BACTERIOLOGY
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Questions and Answers

What is the optimum temperature range for mesophiles?

  • 50-60°C
  • 30-37°C
  • 35-37°C (correct)
  • 15-30°C

    • Which type of bacteria is negatively affected by oxygen?

  • Facultative anaerobes
  • Obligate anaerobes (correct)
  • Psychrophiles
  • Aerobes

    • What is the typical CO2 requirement for bacterial incubation?

  • 20-25%
  • 0-2%
  • 30-35%
  • 5-10% (correct)

    • What pH range is optimized for most bacteria?

    <p>6.5-7.5</p> Signup and view all the answers

    What technique effectively sterilizes using moist heat?

    <p>Autoclaving</p> Signup and view all the answers

    What is the role of catalase in bacteria?

    <p>Neutralizes superoxide radicals</p> Signup and view all the answers

    At what temperature and pressure does the autoclave operate to ensure sterilization?

    <p>121°C, 15 lbs pressure/sq.in.</p> Signup and view all the answers

    Which nutrient is specifically required by some bacteria, but not all?

    <p>Vitamin K</p> Signup and view all the answers

    What is the main outcome of adding water to the components of a gas pak?

    <p>It generates hydrogen and carbon dioxide.</p> Signup and view all the answers

    Which method is NOT typically used for sterilization?

    <p>Bleach disinfection</p> Signup and view all the answers

    Which antibiotic is particularly effective against Clostridium difficile and MRSA?

    <p>Vancomycin</p> Signup and view all the answers

    What is the mechanism of action for aminoglycosides?

    <p>Inhibits protein synthesis on the 30S subunit</p> Signup and view all the answers

    Which antibiotic class includes Aztreonam?

    <p>B-lactams</p> Signup and view all the answers

    Which of the following antibiotics can cause aplastic anemia as a side effect?

    <p>Chloramphenicol</p> Signup and view all the answers

    Which of the following actions is characteristic of sulfa drugs?

    <p>Act as an analogue of PABA</p> Signup and view all the answers

    What distinguishes disinfection from sterilization?

    <p>Disinfection may not eliminate spores.</p> Signup and view all the answers

    Which antibiotic is specifically noted for its use against Pseudomonas aeruginosa?

    <p>Ciprofloxacin</p> Signup and view all the answers

    Which antibiotic can affect bones and teeth in children?

    <p>Tetracycline</p> Signup and view all the answers

    What action does bactericidal antibiotics perform?

    <p>Kills bacteria without host immune help</p> Signup and view all the answers

    Which of the following best describes the action of trimethoprim when combined with sulfonamides?

    <p>It shows synergistic effects enhancing antimicrobial activity</p> Signup and view all the answers

    Linezolid is effective against which type of bacteria?

    <p>Gram-positive, including those resistant to other antibiotics</p> Signup and view all the answers

    Which type of antibiotic is characterized by a narrow spectrum of activity?

    <p>Antibiotics that target only specific groups of bacteria</p> Signup and view all the answers

    What principle does selective toxicity refer to in antimicrobial therapy?

    <p>The drug selectively harms only the bacteria without affecting the host</p> Signup and view all the answers

    Which of the following defines bacteriostatic action?

    <p>It temporarily inhibits bacterial growth, relying on the host for ultimate destruction</p> Signup and view all the answers

    What is the term for a drug interaction where the combined effect is less than expected?

    <p>Antagonism</p> Signup and view all the answers

    Quinupristin/dalfopristin is primarily utilized for treating which type of infection?

    <p>Gram-positive infections, especially vancomycin-resistant Enterococcus faecium</p> Signup and view all the answers

    What is the primary purpose of microaerophiles in relation to oxygen levels?

    <p>Prefer lower oxygen levels than in air</p> Signup and view all the answers

    What is the role of capnophiles in bacterial growth?

    <p>They require higher CO2 levels than in air</p> Signup and view all the answers

    Which of the following best describes complex media used for bacterial growth?

    <p>It contains peptones and extracts providing rich nutrients</p> Signup and view all the answers

    What happens during refrigeration regarding bacterial growth?

    <p>It slows growth without killing the organisms</p> Signup and view all the answers

    What is the effect of osmotic pressure from a hypertonic solution on bacteria?

    <p>It induces plasmolysis in bacterial cells</p> Signup and view all the answers

    What is the function of reducing agents in anaerobic media?

    <p>They bind with oxygen present in the media</p> Signup and view all the answers

    Which of the following methods forms hydroxyl radicals that can damage DNA?

    <p>Radiation</p> Signup and view all the answers

    What is the primary action of phenol as a disinfectant?

    <p>It denatures proteins and damages the membrane</p> Signup and view all the answers

    What is the primary purpose of the Kirby-Bauer method in susceptibility testing?

    <p>To assess the efficacy of antibiotics in inhibiting bacterial growth</p> Signup and view all the answers

    Which condition must be maintained for the Mueller-Hinton agar used in susceptibility testing?

    <p>An ambient air incubation at 35°C</p> Signup and view all the answers

    What does a 'D'-shaped zone of inhibition indicate in inducible strains?

    <p>Inducible beta-lactamase production</p> Signup and view all the answers

    What is the significance of determining the minimum bactericidal concentration (MBC)?

    <p>It reveals the lowest concentration that kills 99.9% of bacteria</p> Signup and view all the answers

    What characteristic does the Modified Hodge test assess in bacteria?

    <p>Resistance to beta-lactam antibiotics</p> Signup and view all the answers

    Which bacterial species is notably associated with carbapenem resistance?

    <p>Klebsiella pneumoniae</p> Signup and view all the answers

    What does the detection of MRSA typically involve?

    <p>Molecular testing for the mecA gene</p> Signup and view all the answers

    Which component is crucial for the growth of certain resistant bacterial strains in culture media?

    <p>Physiologic concentration of calcium and magnesium</p> Signup and view all the answers

    What is the primary mechanism of action for quinupristin/dalfopristin?

    <p>Inhibits protein synthesis</p> Signup and view all the answers

    Which of the following statements correctly differentiates between bactericidal and bacteriostatic actions?

    <p>Bactericidal action leads to irreversible inhibition.</p> Signup and view all the answers

    Which class of antibiotics is effective against Gram-positive bacteria resistant to other antibiotics?

    <p>Oxazolidinones</p> Signup and view all the answers

    What type of spectrum does an antibiotic with narrow spectrum activity have?

    <p>Only targets certain groups of bacteria</p> Signup and view all the answers

    What does the term 'synergism' refer to in the context of drug combinations?

    <p>The combined effect of drugs is greater than the sum of their individual effects.</p> Signup and view all the answers

    Which of the following is a characteristic of broad-spectrum antibiotics?

    <p>Effective against a wide range of bacteria</p> Signup and view all the answers

    What is the effect of selective toxicity in antimicrobial therapy?

    <p>It allows drugs to target microbes without harming host cells.</p> Signup and view all the answers

    Which type of action do bacteriostatic antibiotics perform?

    <p>They inhibit bacterial growth reversibly.</p> Signup and view all the answers

    What should be reported as resistant if an extended-spectrum beta-lactamase (ESBL) is detected?

    <p>All penicillins, cephalosporins, and aztreonam</p> Signup and view all the answers

    Which statement accurately describes the enzyme activity related to resistance?

    <p>Enzyme activity may vary between different strains.</p> Signup and view all the answers

    What could lead to a methicillin zone decrease over time in control organisms?

    <p>Degradation of methicillin during refrigeration</p> Signup and view all the answers

    What is a potential reason for observing a 'zone within a zone' phenomenon during antibiotic susceptibility testing?

    <p>Mixed culture with sensitive and resistant strains</p> Signup and view all the answers

    Which organism is especially noted as a potential ESBL producer?

    <p>Escherichia coli</p> Signup and view all the answers

    What is likely the cause if colonies are found within the zone of inhibition?

    <p>Heavy inoculum leading to overwhelm of antibiotic</p> Signup and view all the answers

    What could explain the observed small zones universally on control plates?

    <p>Overly thin agar depth preventing proper diffusion</p> Signup and view all the answers

    Which statement best describes a method for evaluating potential methicillin resistance?

    <p>Implementing D-test to analyze for E-test discrepancies</p> Signup and view all the answers

    Which method is utilized to find the first plate with no bacterial growth when testing near the minimum inhibitory concentration (MIC)?

    <p>BD Phoenix</p> Signup and view all the answers

    What additional methods can be used for testing fastidious bacteria?

    <p>Supplemented MH for S. pneumoniae</p> Signup and view all the answers

    What could be an effect of having a low pH on agar during disk diffusion testing?

    <p>Tetracycline zone too small</p> Signup and view all the answers

    What is a potential source of error in disk diffusion related to inoculum density?

    <p>Zones uniformly too small</p> Signup and view all the answers

    What condition can cause an aminoglycoside zone to appear too large during testing?

    <p>Calcium and magnesium levels too high</p> Signup and view all the answers

    Which of the following is NOT a modified method for testing slow-growing bacteria?

    <p>Plastic strips impregnated with antimicrobials</p> Signup and view all the answers

    What is a characteristic error linked to tetracycline zone sizes in disk diffusion testing?

    <p>Inoculum preparation errors</p> Signup and view all the answers

    Which test method is described as utilizing strips to determine MIC values for antimicrobials?

    <p>E-test</p> Signup and view all the answers

    What is the primary grouping of antibiotics that inhibits cell wall synthesis?

    <p>B-lactams</p> Signup and view all the answers

    Which antibiotics primarily target the 30S ribosomal subunit to inhibit protein synthesis?

    <p>Tetracyclines</p> Signup and view all the answers

    What is the action of Ciprofloxacin, a member of the quinolines class?

    <p>Inhibits nucleic acid synthesis</p> Signup and view all the answers

    What is a common effect of using Tetracyclines in young children?

    <p>Affects bone and teeth development</p> Signup and view all the answers

    What distinguishes antimicrobial actions of Sulfa drugs from other antibiotics?

    <p>Analogue of PABA</p> Signup and view all the answers

    Which antibiotic is primarily used in combination with penicillin for Enterococcus infections?

    <p>Gentamicin</p> Signup and view all the answers

    What is the major mechanism of action for Chloramphenicol?

    <p>Inhibits protein synthesis</p> Signup and view all the answers

    Which of the following antibiotics is known to be effective against anaerobes and Gram-positive organisms?

    <p>Clindamycin</p> Signup and view all the answers

    What is the result of using an autoclave for sterilization?

    <p>Complete kill of microorganisms including spores</p> Signup and view all the answers

    What is a characteristic feature of the action performed by antibiotics like Erythromycin?

    <p>Inhibits protein synthesis</p> Signup and view all the answers

    What type of bacteria is primarily identified using Bordet-Gengou Agar?

    <p>B. pertussis</p> Signup and view all the answers

    Which medium is used to selectively cultivate Gram positive cocci?

    <p>Columbia Colistin-Nalidixic Acid Agar</p> Signup and view all the answers

    What is the primary purpose of using Thiosulfate Citrate-Bile Sucrose (TCBS) agar?

    <p>Select for Vibrio sp.</p> Signup and view all the answers

    CAMPY-Blood Agar is particularly effective for isolating which of the following bacteria?

    <p>Campylobacter sp.</p> Signup and view all the answers

    Which agar is enriched with hemoglobin and is typically used to grow Haemophilus and Neisseria species?

    <p>Chocolate Agar</p> Signup and view all the answers

    Which medium is specifically used for the cultivation of Leptospira?

    <p>Fletcher's Medium</p> Signup and view all the answers

    What type of bacteria does Phenylethyl Alcohol Agar (PEA) mainly select for?

    <p>Gram positive cocci</p> Signup and view all the answers

    What purpose does Buffered Charcoal Yeast Extract (BCYE) serve in microbiology?

    <p>Cultivate Legionella species</p> Signup and view all the answers

    Which medium is specifically enriched with Hemin, Cystine, and Vitamin K for the growth of anaerobes?

    <p>CDC Anaerobic Blood Agar</p> Signup and view all the answers

    What color change occurs on Cooked or Chopped Meat Medium due to deaminase activity following the addition of 10% FeCl3?

    <p>Bright pink</p> Signup and view all the answers

    Which organism is specifically mentioned in the context of anaerobic media?

    <p>Clostridium difficile</p> Signup and view all the answers

    What characteristic is observed in 6.5% NaCl Broth when incubating certain bacteria?

    <p>Both clear and turbid</p> Signup and view all the answers

    Which of the following options correctly identifies the appearance of the surface on CDC Anaerobic Blood Agar after incubation?

    <p>Nondescript</p> Signup and view all the answers

    What does the presence of a turbid medium in 6.5% NaCl Broth indicate?

    <p>Growth of salt-tolerant organisms</p> Signup and view all the answers

    Which component is essential for culturing anaerobes effectively in enriched media?

    <p>Hemin</p> Signup and view all the answers

    What type of surface color change is observed on Cooked or Chopped Meat Medium due to certain metabolic activities?

    <p>Bright pink</p> Signup and view all the answers

    What is the optimal time for collecting a blood culture specimen for Salmonella typhi?

    <p>First week for blood culture, second week for stool culture</p> Signup and view all the answers

    Which of the following methods is NOT appropriate for microscopy as stated in the diagnostic methods?

    <p>Chemical staining with methylene blue</p> Signup and view all the answers

    Which condition is critical for blood culture collection?

    <p>Blood should be drawn during fever spikes</p> Signup and view all the answers

    What should NEVER be done to spinal fluids when preparing specimens?

    <p>Refrigerate the sample</p> Signup and view all the answers

    What is a criterion for the rejection of specimen samples?

    <p>Presence of preservatives</p> Signup and view all the answers

    In what temperature range are most culture plates incubated?

    <p>35-37°C</p> Signup and view all the answers

    What is the minimum requirement of cultures to draw within a 24-hour period for blood cultures?

    <p>2 cultures, but no more than 3</p> Signup and view all the answers

    Which type of microscopy is specifically useful for observing spirochetes?

    <p>Darkfield microscopy</p> Signup and view all the answers

    Which medium is specifically designed to enhance the pigment production of Bacteroides species?

    <p>Kanamycin-Vancomycin Laked Blood Agar</p> Signup and view all the answers

    What biochemical reaction occurs with the carbohydrate fermentations in the Bacteroides Bile Esculin Agar?

    <p>Red coloration indicates a positive reaction</p> Signup and view all the answers

    Which medium is utilized for the selection of Mycobacterium species?

    <p>Petragnani Agar</p> Signup and view all the answers

    Which indicator is used in carbohydrate fermentation tests within anaerobic media?

    <p>Phenol red</p> Signup and view all the answers

    What characteristic do black colonies signify in Bacteroides Bile Esculin Agar?

    <p>Fermentation of esculin</p> Signup and view all the answers

    Which medium is particularly noted for enhancing grouping and the visibility of metachromatic granules in C. diphtheriae?

    <p>Loeffler's Medium</p> Signup and view all the answers

    Which metabolic reaction in anaerobic media is indicated by the formation of a blurred stab?

    <p>Severe motility</p> Signup and view all the answers

    Which type of colonies are typically associated with the B. fragilis group in anaerobic cultures?

    <p>Black colonies</p> Signup and view all the answers

    Which type of anaerobic media supports most organisms?

    <p>Blood agar</p> Signup and view all the answers

    What is the primary purpose of a gas pak jar in anaerobic culture?

    <p>To create anaerobic conditions</p> Signup and view all the answers

    Which of the following is a characteristic trait of selective agar?

    <p>Inhibits growth of certain organisms</p> Signup and view all the answers

    What dilution of blood to broth is recommended for anaerobic cultures in adults?

    <p>1:10</p> Signup and view all the answers

    Which environment composition is typically used in anaerobic gas generation?

    <p>10% H2, 5% CO2, 85% N2</p> Signup and view all the answers

    What type of media includes chemicals or dyes to differentiate between organisms?

    <p>Differential selective media</p> Signup and view all the answers

    Which type of container is deemed best for culturing fungi and acid-fast organisms?

    <p>Isolator®</p> Signup and view all the answers

    What is the primary characteristic of pre-reduced media used for anaerobic culture?

    <p>Is reduced in oxygen content prior to use</p> Signup and view all the answers

    What is the preferred action to take before collecting a blood culture specimen?

    <p>Thoroughly prep the skin with 70% alcohol and iodine</p> Signup and view all the answers

    Which of the following is NOT a criterion for rejection of a specimen?

    <p>Use of appropriate collection devices</p> Signup and view all the answers

    Which type of microscopy is useful for identifying spirochetes?

    <p>Darkfield microscopy</p> Signup and view all the answers

    What is the optimal temperature for culturing Campylobacter species?

    <p>42°C</p> Signup and view all the answers

    What is the recommended action to ensure integrity in spinal fluid specimen handling?

    <p>Never refrigerate the spinal fluid specimen</p> Signup and view all the answers

    Why should specimens be collected prior to antibiotic therapy?

    <p>To increase the chances of identifying the pathogen</p> Signup and view all the answers

    What should never be done with anaerobic or GC specimens during handling?

    <p>Refrigerate the specimens</p> Signup and view all the answers

    Which of the following dyes is used in fluorescence microscopy for staining?

    <p>Auramine rhodamine</p> Signup and view all the answers

    What is the optimal humidity level required for bacterial culture in specific conditions?

    <p>50-70% humidity</p> Signup and view all the answers

    Which condition is necessary for supporting anaerobic bacteria growth?

    <p>Anaerobic conditions with reduced media</p> Signup and view all the answers

    In collecting blood cultures, what is the recommended minimum dilution of blood to broth for adults?

    <p>1:10 dilution</p> Signup and view all the answers

    Which media type supports the growth of most organisms without selective inhibition?

    <p>Non-selective agar</p> Signup and view all the answers

    How many cultures should be drawn within a 24-hour period?

    <p>At least 2, but no more than 3</p> Signup and view all the answers

    Which type of organisms is best isolated using the Isolator® system?

    <p>Fungi and acid-fast organisms</p> Signup and view all the answers

    For the growth of anaerobic microbes, which environmental gas composition is optimal?

    <p>10% H2, 5% CO2, 85% N2</p> Signup and view all the answers

    What is the role of broth media containing thioglycollate or cysteine?

    <p>To provide anaerobic growth conditions</p> Signup and view all the answers

    What is a common symptom of food poisoning caused by enterotoxins?

    <p>Symptoms appear within 1-5 hours after ingestion</p> Signup and view all the answers

    Which exotoxin is NOT typically associated with Staphylococcus infections?

    <p>Aflatoxin</p> Signup and view all the answers

    Which group of patients is most at risk for infections caused by coagulase negative Staphylococcus?

    <p>Immunocompromised hosts</p> Signup and view all the answers

    What characteristic allows Staphylococcus species to show resistance to penicillin?

    <p>Plasmid-mediated B-lactamase</p> Signup and view all the answers

    Which of the following antibiotics is often used against penicillin-resistant Staphylococcus aureus?

    <p>Methicillin</p> Signup and view all the answers

    What is the primary target of the exotoxin TSST-1 in toxic shock syndrome?

    <p>Immune cells</p> Signup and view all the answers

    What is the primary reason for using 10% KOH in conjunction with Calcofluor White?

    <p>To break down debris and mucous</p> Signup and view all the answers

    Which characteristic is NOT associated with Staphylococcus aureus?

    <p>Commonly forms long chains</p> Signup and view all the answers

    Which of the following infections is NOT typically caused by Staphylococcus aureus?

    <p>Urinary tract infections</p> Signup and view all the answers

    What is the drug of choice for treating methicillin-resistant Staphylococcus aureus (MRSA)?

    <p>Vancomycin</p> Signup and view all the answers

    What is the primary function of the iodine mordant during Gram Staining?

    <p>Forms a complex with the violet dye</p> Signup and view all the answers

    Which statement best describes the colony morphology of Staphylococcus aureus on Blood Agar Plate (BAP)?

    <p>Soft, opaque colonies 2-3 mm in diameter</p> Signup and view all the answers

    What does the presence of catalase positive indicate about a bacterial species?

    <p>It can break down hydrogen peroxide</p> Signup and view all the answers

    Which of the following stains is specifically designed for Mycobacteria?

    <p>Auramine-Rhodamine</p> Signup and view all the answers

    What role does the decolorizer play in the Gram Staining process?

    <p>It removes the complex from Gram-negative cells</p> Signup and view all the answers

    Which of the following is a common feature of infections caused by Staphylococcus aureus?

    <p>Often involves deep tissue and systemic infections</p> Signup and view all the answers

    In identification tests, which characteristic is unique to Staphylococcus aureus as compared to other staphylococci?

    <p>Coagulase positivity</p> Signup and view all the answers

    Which loop calibration is conventionally used for urine colony count plates?

    <p>0.001 ml loop</p> Signup and view all the answers

    Which result is expected from a Gram-positive organism after performing a Gram Stain?

    <p>Purple after crystal violet staining</p> Signup and view all the answers

    How long should stained bacteria be read and reported after the inoculation process?

    <p>18-24 hours</p> Signup and view all the answers

    What is the outcome when using Auramine and Rhodamine for staining?

    <p>Fluorescent orange coloration of Mycobacteria</p> Signup and view all the answers

    Which of the following is a primary stain in microbiological methods?

    <p>Crystal Violet</p> Signup and view all the answers

    What is the purpose of using a calibrated 0.001 ml loop in microbiological procedures?

    <p>To ensure accurate measurement of bacterial colonies</p> Signup and view all the answers

    Which primary stain in microbiology is used alongside a decolorizer to differentiate between Gram-positive and Gram-negative bacteria?

    <p>Crystal Violet</p> Signup and view all the answers

    What is the result obtained when performing the Kinyoun or Ziehl-Neilson stain on Mycobacteria?

    <p>Pink cells indicating acid-fast bacilli</p> Signup and view all the answers

    What characteristic differentiates the staining results of Auramine-Rhodamine from traditional methods?

    <p>Fluorescence under UV light</p> Signup and view all the answers

    In the Gram staining process, what role does the decolorizer play?

    <p>It differentiates between Gram-positive and Gram-negative cells</p> Signup and view all the answers

    Why is methanol or heat used in the Gram staining procedure?

    <p>To fix the cells onto the slide</p> Signup and view all the answers

    What does the use of potassium permanganate in the Auramine-Rhodamine stain primarily accomplish?

    <p>Enhancing the visibility of Mycobacterial cells</p> Signup and view all the answers

    How long should the colonies be read and reported after inoculation?

    <p>18-24 hours</p> Signup and view all the answers

    What is a distinguishing trait of Staphylococcus aureus related to its pathogenicity?

    <p>Has Protein A as a major trait</p> Signup and view all the answers

    What is the primary role of catalase in bacteria?

    <p>To convert hydrogen peroxide into water and oxygen</p> Signup and view all the answers

    What characteristic does Staphylococcus saprophyticus have among urinary tract pathogens?

    <p>Resistant to novobiocin</p> Signup and view all the answers

    What type of infections is Staphylococcus aureus primarily associated with?

    <p>Scalded Skin Syndrome and toxic shock syndrome</p> Signup and view all the answers

    Which group of bacteria is primarily associated with opportunistic infections in immunocompromised patients?

    <p>Coagulase-negative Staphylococci</p> Signup and view all the answers

    What is the primary mechanism of action of vancomycin against bacteria?

    <p>Inhibits cell wall synthesis</p> Signup and view all the answers

    Which statement is true regarding Staphylococcus epidermidis?

    <p>It is coagulase-negative and primarily involved in prosthetic device infections</p> Signup and view all the answers

    Which of the following best describes the role of Streptolysin O?

    <p>Oxygen labile and antigenic</p> Signup and view all the answers

    Which of the following is a feature of Staphylococcus aureus in relation to antibiotic resistance?

    <p>Most strains produce beta-lactamase</p> Signup and view all the answers

    What does a positive coagulase test indicate about the bacteria?

    <p>The organism may be a human pathogen</p> Signup and view all the answers

    What type of hemolytic activity does Streptococcus pyogenes (Group A) exhibit?

    <p>Beta-hemolytic</p> Signup and view all the answers

    What is the main consequence of methicillin resistance in Staphylococcus aureus?

    <p>Limited options for treatment based on antibiotic susceptibility</p> Signup and view all the answers

    What is the expected reaction of the catalase test for Staphylococcus species?

    <p>Rapid formation of bubbles indicating a positive result</p> Signup and view all the answers

    What is a common characteristic of coagulase-negative Staphylococci in relation to infections?

    <p>They are associated with infections in hospitalized patients</p> Signup and view all the answers

    Which Staphylococcus species is most commonly associated with community-acquired infections?

    <p>Staphylococcus aureus</p> Signup and view all the answers

    What effect does storing bacterial cultures at 35-37°C have on Staphylococcus species?

    <p>Promotes optimal growth for testing purposes</p> Signup and view all the answers

    Which bacterium is identified by its growth in 6.5% NaCl and is commonly associated with UTIs and bacteremia?

    <p>Enterococcus</p> Signup and view all the answers

    What characteristic colony morphology distinguishes Streptococcus pneumoniae?

    <p>Alpha hemolytic crater-like colonies</p> Signup and view all the answers

    Which method can be used to identify antibiotic sensitivity of Streptococcus pneumoniae?

    <p>Oxacillin disc sensitivity test</p> Signup and view all the answers

    What laboratory feature is commonly used to identify Enterococcus in culture?

    <p>Growth on bile esculin medium</p> Signup and view all the answers

    Which bacterial species is primarily associated with color cancer?

    <p>bovis</p> Signup and view all the answers

    Which specific hemolytic pattern is typically observed in viridans group streptococci associated with subacute bacterial endocarditis?

    <p>Alpha hemolytic</p> Signup and view all the answers

    What is the hemolysis reaction indicated by the greening around a colony?

    <p>Alpha hemolysis</p> Signup and view all the answers

    What key attribute differentiates Staphylococcus from Streptococcus in terms of catalase activity?

    <p>Staphylococcus is catalase positive</p> Signup and view all the answers

    Which of the following conditions is NOT typically associated with Streptococcus pneumoniae?

    <p>Tonsillitis</p> Signup and view all the answers

    Which condition defines a positive screening for penicillin resistance in S.pneumoniae?

    <p>Hemolytic activity greater than 20 mm</p> Signup and view all the answers

    What type of infection is rarely caused by S.viridans?

    <p>Endocarditis</p> Signup and view all the answers

    What does a 'rusty sputum' indicate in patients and which pathogen is commonly responsible for this symptom?

    <p>Bacterial pneumonia; Streptococcus pneumoniae</p> Signup and view all the answers

    The shaded areas in laboratory results signify what?

    <p>Key reactions</p> Signup and view all the answers

    Which characteristic is incorrectly associated with alpha hemolysis?

    <p>Complete clearing around the colony</p> Signup and view all the answers

    What is the main clinical implication of identifying S.pneumoniae with the mentioned characteristics?

    <p>Potential for bacteremia and pneumonia</p> Signup and view all the answers

    Which colony morphology is associated with S.pneumoniae?

    <p>Crater colonies</p> Signup and view all the answers

    Which organism is characterized by the presence of metachromatic granules and a 'Chinese Letter' arrangement?

    <p>Corynebacterium</p> Signup and view all the answers

    What characteristic movement is associated with Listeria monocytogenes at 25°C?

    <p>Tumbling motility</p> Signup and view all the answers

    Which species causes infections in individuals such as fishermen and veterinarians?

    <p>Erysipelothrix</p> Signup and view all the answers

    What distinguishes Bacillus from other Gram-positive rods regarding hemolysis?

    <p>Strongly beta-hemolytic</p> Signup and view all the answers

    The Elek test is used to determine the production of which of the following?

    <p>Toxin</p> Signup and view all the answers

    Which Gram-positive rod is associated with causing neonatal meningitis and sepsis?

    <p>Listeria</p> Signup and view all the answers

    Which Gram-positive rod is catalase positive and can form spores?

    <p>Bacillus</p> Signup and view all the answers

    What is a significant characteristic of Erysipelothrix when grown in gelatin?

    <p>Test tube brush growth</p> Signup and view all the answers

    What is a key characteristic of Neisseria gonorrhoeae in terms of its growth conditions?

    <p>It requires 5-10% CO2 and may take up to 48 hours for growth.</p> Signup and view all the answers

    Which statement accurately describes Moraxella catarrhalis?

    <p>It usually produces beta-lactamase.</p> Signup and view all the answers

    What distinguishes the colony appearance of Moraxella catarrhalis?

    <p>Colony is hard and has a tendency to 'move over'.</p> Signup and view all the answers

    Which of the following statements is true regarding Neisseria gonorrhoeae?

    <p>It can be confused with Moraxella catarrhalis in clinical specimens.</p> Signup and view all the answers

    What type of infections can Acinetobacter species cause?

    <p>Respiratory infections and urinary tract infections.</p> Signup and view all the answers

    What is the reaction of Neisseria gonorrhoeae on culture media?

    <p>It grows well on chocolate agar and Thayer-Martin agar.</p> Signup and view all the answers

    Which of the following properties is true about Acinetobacter species?

    <p>They exhibit a high level of resistance to many antibiotics.</p> Signup and view all the answers

    In the context of bacterial meningitis, what is a common finding in the CSF for infections caused by Gram-negative cocci?

    <p>Presence of neutrophils.</p> Signup and view all the answers

    What condition must be met for the organism S.enterica to cause infection?

    <p>A large number of bacteria (&gt;100,000) is necessary.</p> Signup and view all the answers

    Which biochemical test indicates a positive result for H2S production?

    <p>Precipitation of a black pigment.</p> Signup and view all the answers

    Which of the following correctly describes the structure related to Plesiomonas?

    <p>It is motile due to lophotrichous flagella.</p> Signup and view all the answers

    Which biochemical test result indicates a strong preference for lysine?

    <p>Lysine positive.</p> Signup and view all the answers

    What is the expected result of the ONPG test in the presence of B-d-galactosidase?

    <p>Yellow coloration.</p> Signup and view all the answers

    Which serotype of S.enterica is primarily associated with septicemia?

    <p>S.cholerasuis.</p> Signup and view all the answers

    What reagent is used to confirm positive nitrate reduction in bacteria?

    <p>Zinc powder.</p> Signup and view all the answers

    What does a positive urea test indicate in bacterial cultures?

    <p>Ammonia production, resulting in a color change.</p> Signup and view all the answers

    Which selective media uses Eosin Y as a differentiating agent?

    <p>Eosin Methylene Blue (EMB)</p> Signup and view all the answers

    In Hektoen-Enteric (HE) agar, what is the H2S indicator that produces a black precipitate?

    <p>Sodium Thiosulfate</p> Signup and view all the answers

    Which of the following is a key reaction that differentiates Enterobacter from Citrobacter?

    <p>Voges-Proskauer test</p> Signup and view all the answers

    What is the color of lactose-positive colonies on MacConkey Agar?

    <p>Dark Pink</p> Signup and view all the answers

    In which agar is Salicin used as a differentiating agent?

    <p>Hektoen-Enteric (HE) Agar</p> Signup and view all the answers

    Which reaction is variable (v) in the biochemical tests for Escherichia coli?

    <p>Voges-Proskauer</p> Signup and view all the answers

    Which of the following exhibits a negative reaction for hydrogen sulfide production on KIA tests?

    <p>Klebsiella</p> Signup and view all the answers

    Which agar has a transparent appearance for lactose-negative colonies?

    <p>Salmonella-Shigella (SS) Agar</p> Signup and view all the answers

    What is the acid-base indicator used in MacConkey Agar?

    <p>None</p> Signup and view all the answers

    Which organism shows a positive reaction for deaminase activity?

    <p>Proteus</p> Signup and view all the answers

    What characteristic distinguishes Escherichia coli from Enteroinvasive E. coli (EIEC)?

    <p>EIEC penetrates epithelial cells in the large intestine.</p> Signup and view all the answers

    Which strain of Shigella is associated with the most severe cases of bacillary dysentery?

    <p>Shigella dysenteriae</p> Signup and view all the answers

    What type of toxin is produced by Enterotoxigenic E. coli (ETEC)?

    <p>Both heat labile and heat stable toxins</p> Signup and view all the answers

    Which characteristic applies solely to the strain 0157:H7 of Enterohemorrhagic E. coli (EHEC)?

    <p>It produces a Shigella-like toxin.</p> Signup and view all the answers

    What is the minimum number of organisms needed for the disease caused by Bacillary dysentery?

    <p>Less than 200 organisms</p> Signup and view all the answers

    Which statement correctly describes the lactose fermentation characteristic of Shigella species?

    <p>All Shigella species are lactose negative.</p> Signup and view all the answers

    Qual es le resultato positive in le agar de ferro de lysine (LIA)?

    <p>Butt deveni purpureo</p> Signup and view all the answers

    Qual dye es utilizate como indicatore in le detection de acetylmethylcarbinol?

    <p>Bromcresol purple</p> Signup and view all the answers

    Qual es le percentuale de glucose in le media MIO?

    <p>0.1%</p> Signup and view all the answers

    Le agar de lysine iron (LIA) ha un indicatore de quale gas?

    <p>H2S</p> Signup and view all the answers

    Qual es le colore indicative de un reaction positive in le media MIO?

    <p>Purpureo</p> Signup and view all the answers

    Qual de le sequente non es un resultato positive pro acetoin detection?

    <p>Verde</p> Signup and view all the answers

    Le que type de resultato in KIA representa un aumento de fermento de glucose?

    <p>Acido-acido (A/A)</p> Signup and view all the answers

    Qual es le resultato in KIA quando H2S es presente?

    <p>Slant deveni negro</p> Signup and view all the answers

    Quo tipo de fermentatio resulta in un butt jaune in un medio de Kligler Iron Agar?

    <p>Fermentatio de glucose</p> Signup and view all the answers

    Qual es le significato de un slant jaune in un test de Kligler Iron Agar?

    <p>Lactose o sucrose es fermentate</p> Signup and view all the answers

    Quale caracteristica es specific a Klebsiella pneumoniae?

    <p>Capasitate de causar pneumonia lobar</p> Signup and view all the answers

    Qual de le sequentes bacterias es indole positive?

    <p>Proteus vulgaris</p> Signup and view all the answers

    Qual test verifica la capacitate de bacteria a decarboxylate amino acidos?

    <p>Test de decarboxylase</p> Signup and view all the answers

    Quale de le sequente afirmations es ver de Citrobacter?

    <p>Opportunista</p> Signup and view all the answers

    In un test de indole, qual es le resultato positive?

    <p>Pink</p> Signup and view all the answers

    Quale bacterium non es un motile?

    <p>Klebsiella</p> Signup and view all the answers

    Qual es le resultato de un test de citrate quando le medio es positive?

    <p>Blu</p> Signup and view all the answers

    Qual resulta indicara la production de H2S in un medio de Kligler Iron Agar?

    <p>Butt nigre</p> Signup and view all the answers

    Quale bacterium es asociated con la enfermedad de cuela mesenterica?

    <p>Yersinia pseudotuberculosis</p> Signup and view all the answers

    Qual es le resultato positive in un test de urease?

    <p>Slant rosa</p> Signup and view all the answers

    Quales caracteristicas distingue la specie Yersinia enterocolitica?

    <p>Invasiva e toxigenica</p> Signup and view all the answers

    Quo es le reagent in le test de indole?

    <p>p-dimethyl-aminobenzaldehyde</p> Signup and view all the answers

    Quale de le sequentes affirmations es vera pro Proteus mirabilis?

    <p>Motile</p> Signup and view all the answers

    Quale substantia non es considerata un caracteristica de Serratia?

    <p>Indole negative</p> Signup and view all the answers

    Quo es le resultado positive quando un organism realmente produce phenylalanine deaminase?

    <p>Green coloration</p> Signup and view all the answers

    Qual de istas caracteristicas es typic per organismos gram-negativ non-fermentadores?

    <p>Oxidase positive</p> Signup and view all the answers

    Qual es le interpretazione de un tub macconkey con coloration verde?

    <p>Asaccharolytic</p> Signup and view all the answers

    Qual organismo es general in relation a infecciones in pacientes con fibrose cystica?

    <p>Burkholderia cepacia</p> Signup and view all the answers

    Qual pigmento non es typic per Pseudomonas aeruginosa?

    <p>Xanthomonas</p> Signup and view all the answers

    Quo indica un tub semi-solide incubate in un modo con oxygeno restrictate, donde le parte aperte es yellow e le parte claude es green?

    <p>Oxidizer properties</p> Signup and view all the answers

    Quo es le resultato de un tige OF media que es color yellow in le tige aperte e verde in le tige claude?

    <p>Oxidizer</p> Signup and view all the answers

    Qual de iste organismos es oxydase positive e cuje crescimento es tipic in le cultura de MacConkey?

    <p>Pseudomonas aeruginosa</p> Signup and view all the answers

    Quale de iste bacterias es associato con odore de sulfuro?

    <p>Yersinia</p> Signup and view all the answers

    Quale action es le conde de protection indicale quando urgen in le deserto?

    <p>Porta un cap</p> Signup and view all the answers

    Le que bacteria es notabile pro su association con geysers?

    <p>Serratia</p> Signup and view all the answers

    Quale statement es ver si considerante H2S?

    <p>H2S es un indicatore de contaminazione microbiologica.</p> Signup and view all the answers

    Quale de iste bacterias non produce H2S?

    <p>Klebsiella</p> Signup and view all the answers

    Quale descrition correcte reflecte un caso de 'firecracker' in un desert?

    <p>Iste eventus es periculose e non debe esser ignorate.</p> Signup and view all the answers

    Which organism is characterized by being motile with polar flagella and having hemolytic colonies on BAP?

    <p>Aeromonas</p> Signup and view all the answers

    What color is Vibrio cholerae on TCBS agar?

    <p>Yellow</p> Signup and view all the answers

    Which biochemical test is positive for Campylobacter jejuni?

    <p>Catalase positivity</p> Signup and view all the answers

    Which characteristic differentiates Vibrio species from enteric bacteria?

    <p>Lactose fermentation</p> Signup and view all the answers

    Which type of growth medium is used for isolating Campylobacter jejuni?

    <p>CAMPY agar</p> Signup and view all the answers

    What is a typical clinical presentation of V. cholerae infection?

    <p>Profuse diarrhea described as 'rice water' stools</p> Signup and view all the answers

    What treatment is commonly effective for infections caused by Campylobacter jejuni?

    <p>Erythromycin or tetracycline</p> Signup and view all the answers

    Which compound do Vibrio species test positive for that aids in their classification?

    <p>Nitrate</p> Signup and view all the answers

    Which species of Brucella is known to cause brucellosis in cows?

    <p>B. abortus</p> Signup and view all the answers

    Which Brucella species demonstrates a positive result for the presence of H2S?

    <p>B. abortus</p> Signup and view all the answers

    What unique characteristic regarding nutrient consumption is associated with B. abortus?

    <p>It consumes Thionine.</p> Signup and view all the answers

    Which species of Brucella is primarily associated with causing disease in goats?

    <p>B. melitensis</p> Signup and view all the answers

    Which of the following Brucella species has an uncertain result for Thionine consumption?

    <p>B. suis</p> Signup and view all the answers

    What is the incubation period during which brucellosis can be confirmed through blood culture?

    <p>First two weeks</p> Signup and view all the answers

    Which characteristic differentiates Yersinia pestis from Francisella tularensis?

    <p>Presence of bi-polar staining</p> Signup and view all the answers

    What is a common feature of Pasteurella multocida?

    <p>Produces a 'mousy' odor</p> Signup and view all the answers

    Which organism requires Ascitic Fluid Sample for diagnosis?

    <p>Streptobacillus moniliformis</p> Signup and view all the answers

    What kind of media supports the growth of Francisella tularensis?

    <p>Cystine-Glucose Media</p> Signup and view all the answers

    Which pathogen is primarily associated with the disease known as 'Rabbit Fever'?

    <p>Francisella tularensis</p> Signup and view all the answers

    What is the biosafety level of Yersinia pestis?

    <p>Biosafety level 3</p> Signup and view all the answers

    What characteristic is used to distinguish the colonies of Streptobacillus moniliformis?

    <p>String of pearls</p> Signup and view all the answers

    Which organism is NOT primarily transmitted through animal bites?

    <p>Yersinia pestis</p> Signup and view all the answers

    What is the purpose of using chocolate agar in bacterial culture?

    <p>To facilitate the breakdown of red blood cells and release growth factors</p> Signup and view all the answers

    Which statement best describes the Regan/Lowe medium?

    <p>It has a longer shelf life compared to chocolate agar</p> Signup and view all the answers

    What is a key characteristic of S. aureus in relation to satellite colonies?

    <p>It produces V factor and allows Haemophilus growth nearby</p> Signup and view all the answers

    What is the recommended incubation period for bacterial colonies in this context?

    <p>72-96 hours at 35°C</p> Signup and view all the answers

    Which factor is necessary for growing certain bacterial species in a hemolytic area?

    <p>5% rabbit or horse blood</p> Signup and view all the answers

    What is the main reason for moving away from cough plates for specimen collection?

    <p>NP swabs provide a better sample directly from the nasal passages</p> Signup and view all the answers

    What is the role of PCR in the context of bacterial identification?

    <p>To confirm the identity of the bacteria present</p> Signup and view all the answers

    Which type of bacteria is effectively grown using Bordet-Gengou medium?

    <p>Specific respiratory pathogens such as Bordetella pertussis</p> Signup and view all the answers

    What is a common clue indicating an anaerobic infection?

    <p>Foul odor to specimen</p> Signup and view all the answers

    Which of the following techniques is utilized for anaerobic culture?

    <p>Jar technique with Gas Pak jar</p> Signup and view all the answers

    What is indicated by the presence of sulfur granules in a specimen?

    <p>Possible presence of an anaerobic organism</p> Signup and view all the answers

    Which of the following is one of the classic indications of anaerobic infection?

    <p>Gas in the specimen</p> Signup and view all the answers

    In anaerobic culture, what role do indicators like methylene blue or resazurin play?

    <p>Signal the presence of oxygen by changing color</p> Signup and view all the answers

    What might be a characteristic finding in blood containing exudates from an anaerobic infection?

    <p>Black discoloration</p> Signup and view all the answers

    What is a potential problem if an organism fails to grow when cultured aerobically?

    <p>The organism is likely anaerobic.</p> Signup and view all the answers

    What can contribute to the failure of organism growth on aerobic culture when an anaerobic organism is suspected?

    <p>Administration of aminoglycosides</p> Signup and view all the answers

    Which of the following organisms is associated with a 'bleachy' odor and can pit agar?

    <p>Eikenella corrodens</p> Signup and view all the answers

    What type of abscess is commonly associated with Aggregatibacter actinomycetemcomitans?

    <p>Jaw abscesses</p> Signup and view all the answers

    Which organism is known to give false positive Gram reactions due to its rosette grouping?

    <p>Cardiobacterium hominis</p> Signup and view all the answers

    Which colony type is described as having a center with 4-6 pointed stars?

    <p>Aggregatibacter actinomycetemcomitans</p> Signup and view all the answers

    What type of infection is Kingella kingae primarily associated with in children?

    <p>Septic arthritis</p> Signup and view all the answers

    What is a primary feature of Legionella pneumophila serogroups 1 and 6 in relation to human illness?

    <p>It leads to 75% of Legionnaires' disease cases.</p> Signup and view all the answers

    Which feature is common to Cardiobacterium hominis and Eikenella corrodens?

    <p>They both cause endocarditis.</p> Signup and view all the answers

    Which substance is used to determine bacterial sensitivity to ampicillin in urethritis cases?

    <p>Beta lactamase</p> Signup and view all the answers

    What is a distinguishing characteristic of the HACEK group of bacteria?

    <p>They are commonly associated with endocarditis.</p> Signup and view all the answers

    How is Spirillum minor primarily diagnosed in clinical settings?

    <p>Visualizing under darkfield microscopy or Giemsa stain.</p> Signup and view all the answers

    Which organism is recognized for its characteristic spreading, corroding colonies?

    <p>Kingella kingae</p> Signup and view all the answers

    What is a common environmental source for L.pneumophila infections?

    <p>Contaminated potable water sources.</p> Signup and view all the answers

    Which antibiotic is known to be resistant in treating Mycoplasma hominis infections?

    <p>Erythromycin</p> Signup and view all the answers

    Which method is NOT typically effective in growing species involved in Mycoplasma infections?

    <p>Artificial media cultivation.</p> Signup and view all the answers

    What is a significant clinical complication associated with M.hominis colonization?

    <p>Postpartum fever.</p> Signup and view all the answers

    Which factor contributes to the corkscrew motility observed in spirilla bacteria?

    <p>Bipolar tufts of flagella.</p> Signup and view all the answers

    What is the primary culture requirement for the microorganism discussed in the characteristics section?

    <p>Growth only on chocolate agar</p> Signup and view all the answers

    Which of the following correctly describes the staining characteristics of the microorganism mentioned in the content?

    <p>Does not stain with Gram's stain but can be stained with Dienes stain</p> Signup and view all the answers

    What appearance does the center of the colony take when grown on the special media mentioned?

    <p>Like an inverted 'fried egg'</p> Signup and view all the answers

    What condition is associated with the painful genital ulcers resulting from the microorganism discussed?

    <p>Chancroid</p> Signup and view all the answers

    Which antibiotic is suggested for the treatment of the atypical pneumonia caused by M. pneumoniae?

    <p>Erythromycin</p> Signup and view all the answers

    What diagnostic feature can be identified with a cold agglutinin titer in the context of M. pneumoniae infection?

    <p>False positive result in rapid plasma reagin (RPR)</p> Signup and view all the answers

    What best describes the relationship between Ureaplasma urealyticum and other infections?

    <p>It is a non-gonococcal, non-chlamydial infection</p> Signup and view all the answers

    What specific media composition is essential for the growth of the microorganisms discussed?

    <p>Media that contains sterols</p> Signup and view all the answers

    What is a common characteristic of the morphology of acid-fast bacteria?

    <p>Slim gram-variable rods</p> Signup and view all the answers

    Which staining method utilizes heat during its procedure?

    <p>Ziehl-Neilsen stain</p> Signup and view all the answers

    What determines the significance of the number of acid-fast bacteria seen on a smear?

    <p>Any number seen on a smear is significant</p> Signup and view all the answers

    What additional requirement is necessary for the growth of some acid-fast bacteria?

    <p>Specific CO2 enrichment</p> Signup and view all the answers

    For collecting sputum specimens, which procedure is advised?

    <p>First morning sputum on three consecutive mornings</p> Signup and view all the answers

    What is the expected timeframe for the growth of acid-fast bacteria in culture?

    <p>3-6 weeks</p> Signup and view all the answers

    Which type of culture system is commonly used for rapid growth and susceptibility testing of bacteria?

    <p>Automated liquid culture systems</p> Signup and view all the answers

    In the context of acid-fast bacteria, what specifically do all stains rely on?

    <p>Presence of mycolic acid</p> Signup and view all the answers

    Which organism is characterized by molar tooth colonies of gram-positive branching rods?

    <p>Actinomyces</p> Signup and view all the answers

    What is a notable characteristic of Bacteroides fragilis when grown on BBE agar?

    <p>Forms dark colonies larger than 1mm</p> Signup and view all the answers

    Which characteristic is true of Fusobacterium nucleatum?

    <p>Exhibits thin, fusiform rods</p> Signup and view all the answers

    Which organism is primarily associated with pseudomembranous colitis?

    <p>Clostridium difficile</p> Signup and view all the answers

    How does Fusobacterium mortiferum's morphology differ from other Fusobacterium species?

    <p>It is highly pleomorphic</p> Signup and view all the answers

    What type of spores do Clostridium tetani produce?

    <p>Terminal spores</p> Signup and view all the answers

    What general type of colony appearance is associated with Bacteroides ureolyticus?

    <p>Black colonies on BBE</p> Signup and view all the answers

    Which organism produces a weakly positive lipase reaction?

    <p>Fusobacterium mortiferum</p> Signup and view all the answers

    What differentiates Clostridium perfringens from other Clostridium species?

    <p>It produces a double zone of hemolysis</p> Signup and view all the answers

    What type of antibiotic resistance is often observed in Clostridium difficile?

    <p>Emerging resistance to multiple antibiotics</p> Signup and view all the answers

    Which organism is associated with Rickettsial Pox?

    <p>Rickettsia akari</p> Signup and view all the answers

    What method is used to confirm infection by Coxiella burnetti?

    <p>Complement fixation test</p> Signup and view all the answers

    Which vector is responsible for transmitting Typhus Fever?

    <p>Lice</p> Signup and view all the answers

    Which Rickettsial infection is characterized by a rash on the palms of the hands and soles of the feet?

    <p>Rocky Mountain Spotted Fever</p> Signup and view all the answers

    What growth requirement medium is used for culturing Mycobacteria?

    <p>Lowenstein-Jensen</p> Signup and view all the answers

    Which element is integral in dispersing colonies in liquid media when culturing Mycobacteria?

    <p>Tween 80</p> Signup and view all the answers

    What is the main vector for Rickettsia typhi, known for causing Murine Typhus?

    <p>Rat Fleas</p> Signup and view all the answers

    What is the characteristic titer level indicative of a Rickettsial infection?

    <p>1:160</p> Signup and view all the answers

    What is a characteristic feature that distinguishes Actinomyces israelii colonies?

    <p>Molar Tooth appearance</p> Signup and view all the answers

    What is the primary method through which Leptospira is transmitted to humans?

    <p>Through water contaminated with animal urine</p> Signup and view all the answers

    Which antibiotic is Actinomyces israelii known to be sensitive to?

    <p>Penicillin</p> Signup and view all the answers

    What is the estimated time frame for the primary lesion of syphilis to heal without treatment?

    <p>3-8 weeks</p> Signup and view all the answers

    What characteristic distinguishes Chlamydia trachomatis in terms of growth dependency?

    <p>It is dependent on a host for ATP.</p> Signup and view all the answers

    Which of the following best describes the growth characteristics of Actinomyces israelii in culture media?

    <p>No growth on artificial media</p> Signup and view all the answers

    Which laboratory technique is best for identifying Borrelia species in blood samples?

    <p>Giemsa stain</p> Signup and view all the answers

    What common diagnostic technique is employed for identifying syphilis?

    <p>Serological tests</p> Signup and view all the answers

    What is the typical time frame for the latent stage of syphilis to occur after initial infection?

    <p>2-20 years</p> Signup and view all the answers

    What is a clinical manifestation of Chlamydia trachomatis infection in females?

    <p>Salpingitis</p> Signup and view all the answers

    Which group is characterized as obligate intracellular parasites?

    <p>Chlamydia species</p> Signup and view all the answers

    Which of the following statements is true regarding the survival and growth of Chlamydia?

    <p>It can grow in Fletcher's semi-solid media provided specific conditions.</p> Signup and view all the answers

    Which type of infection can Chlamydia trachomatis be transmitted to newborns?

    <p>Conjunctivitis</p> Signup and view all the answers

    What is a significant characteristic of Borrelia's ability to cause relapsing fever?

    <p>It can mutate to evade the immune response.</p> Signup and view all the answers

    Which method is used for laboratory diagnosis of Chlamydia trachomatis?

    <p>Indirect fluorescent antibody (FA) test</p> Signup and view all the answers

    Which of the following best explains the mechanism behind the relapses seen in Borrelia infections?

    <p>Mutation of surface antigens during the disease.</p> Signup and view all the answers

    Which type of microorganism produces pigment only in the presence of light?

    <p>Photochromogen</p> Signup and view all the answers

    Which classification describes bacteria that do not produce any pigment?

    <p>Non-photochromogen</p> Signup and view all the answers

    What is the characteristic growth rate of a rapid grower?

    <p>Growth in &lt; 7 days</p> Signup and view all the answers

    Which organism is most likely to be considered a pathogen in the throat or oropharynx?

    <p>Streptococcus Group A</p> Signup and view all the answers

    Which of the following bacteria is associated with the presence of Neisseria in the throat?

    <p>Alpha Strep</p> Signup and view all the answers

    Which type of pigment-producing bacteria generates pigment in both light and dark conditions?

    <p>Scotochromogen</p> Signup and view all the answers

    In a throat culture, what organism would NOT be expected as part of the normal flora?

    <p>Strep Group A</p> Signup and view all the answers

    What differentiates a scotochromogen from a non-photochromogen?

    <p>Pigment production in darkness</p> Signup and view all the answers

    Which organism is associated with Rickettsial Pox and is primarily spread by house mites?

    <p>R. akari</p> Signup and view all the answers

    What vector is involved in the transmission of Typhus Fever caused by R. prowazekii?

    <p>Lice</p> Signup and view all the answers

    Which of the following organisms is confirmed to cause Q Fever and requires a CF test for confirmation?

    <p>Coxiella burnetti</p> Signup and view all the answers

    Which of these tests is utilized for detecting Rickettsial antibodies through the use of Proteus antigens?

    <p>Weil-Felix test</p> Signup and view all the answers

    Which species is characterized by a rash present on the palms of the hands and soles of the feet?

    <p>R. rickettsiae</p> Signup and view all the answers

    Which organism is primarily identified by its small gram-negative coccobacilli structure?

    <p>R. rickettsiae</p> Signup and view all the answers

    What is the minimum fourfold rise in titer indicated in serological tests for confirming rickettsial infections?

    <p>1:160 titer</p> Signup and view all the answers

    Which vector is responsible for the transmission of Rocky Mountain Spotted Fever?

    <p>Ticks</p> Signup and view all the answers

    Which organism is primarily associated with infections in neonates?

    <p>E.coli</p> Signup and view all the answers

    What type of bacteria are commonly involved in deep wounds or abscesses?

    <p>Anaerobes and aerobes</p> Signup and view all the answers

    Which organism is considered pathogenic in immunocompromised patients with prosthetic heart devices?

    <p>Any organism</p> Signup and view all the answers

    What is a specific characteristic of blood specimens collected for microbiological analysis?

    <p>They are normally sterile</p> Signup and view all the answers

    Which bacteria are most commonly isolated in superficial wounds such as pustules and dermatitis?

    <p>Strep Group A and S.aureus</p> Signup and view all the answers

    What indication is assessed through colony count in urine specimens?

    <p>Urinary Tract Infection (UTI)</p> Signup and view all the answers

    Which of the following is true regarding specimen collection from deep wounds?

    <p>The method depends on the site of the wound.</p> Signup and view all the answers

    Which bacteria is primarily associated with peptic ulcers?

    <p>Helicobacter pylori</p> Signup and view all the answers

    Which characteristic is unique to Mycobacterium leprae in comparison to other mycobacteria?

    <p>Grows best in armadillo footpads</p> Signup and view all the answers

    What is the primary disease caused by Mycobacterium avium complex?

    <p>Pulmonary disease</p> Signup and view all the answers

    Which tests can be used to differentiate between various Mycobacterium species?

    <p>Niacin production</p> Signup and view all the answers

    Which of the following statements about Mycobacterium avium complex is false?

    <p>It thrives in sunlight</p> Signup and view all the answers

    In what unique environmental condition does Mycobacterium leprae primarily grow?

    <p>In armadillo footpads</p> Signup and view all the answers

    Which characteristic does NOT apply to Mycobacterium tuberculosis?

    <p>Negative for acid-fastness</p> Signup and view all the answers

    Which of these mycobacterial species can be identified primarily through the presence of non-pigmented colonies on LJ media?

    <p>Mycobacterium avium complex</p> Signup and view all the answers

    Which condition is primarily associated with infections from Mycobacterium avium complex?

    <p>Immunocompromised patients</p> Signup and view all the answers

    What is the primary reason mycobacteria do not gram stain well?

    <p>They have high lipid content in their wall.</p> Signup and view all the answers

    Which type of staining method is classified as a 'cold' acid fast method?

    <p>Kinyoun stain</p> Signup and view all the answers

    What is the recommended incubation temperature for optimum growth of most mycobacteria?

    <p>36°C</p> Signup and view all the answers

    Which component is NOT used in the Lowenstein-Jensen growth medium?

    <p>Carbohydrates</p> Signup and view all the answers

    How long does it typically take for mycobacteria to grow in culture?

    <p>3-6 weeks</p> Signup and view all the answers

    What is the role of Tween 80 in mycobacterial culture media?

    <p>To aid in dispersing colonies</p> Signup and view all the answers

    Which technique is used for rapid growth and susceptibility testing of mycobacteria?

    <p>Automated liquid culture systems</p> Signup and view all the answers

    What staining method is specifically associated with the presence of mycolic acids in bacteria?

    <p>Acid fast stain</p> Signup and view all the answers

    Which statement correctly describes viruses?

    <p>Viruses infect specific cell types.</p> Signup and view all the answers

    What is a common characteristic of RNA viruses mentioned?

    <p>They include viruses responsible for diseases like yellow fever.</p> Signup and view all the answers

    Which of the following is NOT a feature of viruses?

    <p>They are capable of independent metabolism.</p> Signup and view all the answers

    Which disease is NOT associated with flaviviruses?

    <p>Measles</p> Signup and view all the answers

    What primarily distinguishes viruses from bacteria?

    <p>Viruses are made up of nucleic acid and a protein coat.</p> Signup and view all the answers

    Which of the following correctly identifies the reproduction mode of viruses?

    <p>They require host cells for their reproduction.</p> Signup and view all the answers

    Which virus is primarily associated with chronic fatigue syndrome?

    <p>Epstein-Barr Virus (EBV)</p> Signup and view all the answers

    Which of the following statements regarding Human Papillomavirus (HPV) is accurate?

    <p>Certain serotypes of HPV are associated with cervical carcinoma.</p> Signup and view all the answers

    Which of the following viruses is associated with serious congenital abnormalities and is contraindicated in pregnancy?

    <p>Rubivirus</p> Signup and view all the answers

    What is a common method used for diagnosing Hepatitis B Virus (HBV)?

    <p>ELISA techniques</p> Signup and view all the answers

    What type of virus is known to cause severe respiratory infections predominantly in young children and leads to the formation of giant multinucleated cells?

    <p>Respiratory Syncytial Virus (RSV)</p> Signup and view all the answers

    Which of the following viruses is naturally occurring only in humans and can lead to aseptic meningitis?

    <p>Poliovirus</p> Signup and view all the answers

    Which of the following diseases is not caused by a DNA virus listed in the content?

    <p>Influenza</p> Signup and view all the answers

    The virus associated with acute infectious infantile diarrhea, which can lead to serious complications like death in infants, is:

    <p>Rotavirus</p> Signup and view all the answers

    Which virus is most commonly associated with congenital infections?

    <p>Cytomegalovirus (CMV)</p> Signup and view all the answers

    What is the primary cause of smallpox outbreaks in laboratory settings today?

    <p>Accidental exposure to stored cultures</p> Signup and view all the answers

    What is the primary reservoir for Rhabdovirus, which is known for causing rabies?

    <p>Wildlife</p> Signup and view all the answers

    Which of the following viruses utilizes EIA techniques and is confirmed by Western Blot for testing?

    <p>HIV-I</p> Signup and view all the answers

    Which type of infections are primarily caused by Herpes Simplex Virus type II?

    <p>Genital infections (STD)</p> Signup and view all the answers

    What is a notable characteristic of the Poxvirus?

    <p>It is eradicated but may still cause outbreaks in labs.</p> Signup and view all the answers

    What category do both Human T-Cell Leukemia Virus I and II belong to, based on their characteristics?

    <p>Retrovirus</p> Signup and view all the answers

    Which virus has been associated with the common cold?

    <p>Rhinovirus</p> Signup and view all the answers

    What is a primary characteristic of viral nucleic acid compared to cellular nucleic acid?

    <p>Can be either DNA or RNA</p> Signup and view all the answers

    What is the role of pre- and post-convalescent sera in specimen collection and handling for virology?

    <p>They are shipped on dry ice to preserve integrity.</p> Signup and view all the answers

    Which method is utilized for amplifying nucleic acid sequences in virology?

    <p>Polymerase chain reaction (PCR)</p> Signup and view all the answers

    How does the PCR method function in terms of nucleic acid amplification?

    <p>It carries out cycles that double the targeted nucleic acid product.</p> Signup and view all the answers

    What is the significance of using fetal calf serum in viral culture media?

    <p>It provides nutrients necessary for viral replication.</p> Signup and view all the answers

    What does the EIA in laboratory methods for virology detect?

    <p>The presence of viral antibodies or antigens</p> Signup and view all the answers

    Which laboratory technique allows visualization of viruses at a structural level?

    <p>Electron microscopy</p> Signup and view all the answers

    Which component is essential in transport media for viral culture to ensure viability?

    <p>Antibiotics and nutrients</p> Signup and view all the answers

    What organism is indicated by a 'rice water stool' in patients?

    <p>Vibrio cholerae</p> Signup and view all the answers

    Which organism is likely to be isolated from bluish purulent head lesions?

    <p>Pseudomonas aeruginosa</p> Signup and view all the answers

    What is the typical pressure and temperature for autoclave sterilization?

    <p>15 lbs pressure, 121 °C for 15 min</p> Signup and view all the answers

    What does a gram-stained smear from a genital soft chancre showing small gram-negative rods arranged in tangled chains suggest?

    <p>Haemophilus ducreyi</p> Signup and view all the answers

    Which virus is primarily associated with the development of acute infectious infantile diarrhea characterized by 'rice water stools'?

    <p>Rotavirus</p> Signup and view all the answers

    What is typically observed in the brain tissue for diagnosing rabies in infected animals?

    <p>Negri bodies</p> Signup and view all the answers

    Which organism is primarily associated with causing acute gastroenteritis characterized by bloody diarrhea?

    <p>Shigella dysenteriae</p> Signup and view all the answers

    What is the primary specimen type recommended for diagnosing epiglottitis?

    <p>Throat swab</p> Signup and view all the answers

    For viral culture transportation, which medium is most appropriate?

    <p>Nutrient medium with antibiotics</p> Signup and view all the answers

    Which of the following is NOT used as a primary isolation medium?

    <p>Nutrient broth</p> Signup and view all the answers

    What typical result is demonstrated by Campylobacter jejuni?

    <p>Catalase negative</p> Signup and view all the answers

    Which organism is most likely responsible for a vaginal specimen showing a 'fishy' odor when mixed with 10% KOH?

    <p>Gardnerella vaginalis</p> Signup and view all the answers

    A photochromogenic mycobacterium isolated at 30°C is most likely which species?

    <p>M. marinum</p> Signup and view all the answers

    Which specimen type is least effective for detecting the hallmark of rabies?

    <p>Blood</p> Signup and view all the answers

    Which acute infectious condition is not caused by a virus listed in the options?

    <p>Botulism caused by Hantavirus</p> Signup and view all the answers

    Which statement describes a characteristic that helps distinguish non-motile rods from motile rods?

    <p>Temperature preference of 42°C</p> Signup and view all the answers

    Which medium is inappropriate when transporting specimens for viral cultures?

    <p>Anaerobic containers</p> Signup and view all the answers

    Which organism is most likely implicated in septicemia and pulmonary infections based on its characteristics?

    <p>Pseudomonas aeruginosa</p> Signup and view all the answers

    Which characteristic is commonly used to differentiate between Citrobacter and Salmonella?

    <p>H2S production</p> Signup and view all the answers

    In evaluating a sputum specimen, what collection characteristic would indicate an appropriate sample?

    <blockquote> <p>25 epithelial cells, &gt; 25 white cells</p> </blockquote> Signup and view all the answers

    When testing for possible Streptococcus pneumoniae, which specific test should be performed?

    <p>Optochin susceptibility</p> Signup and view all the answers

    Which statement correctly describes a feature of Serratia marcescens?

    <p>Is known for its unique chromogenic properties</p> Signup and view all the answers

    What is the significance of a clean catch urine specimen showing gram-positive cocci that are catalase positive?

    <p>Suggests an infection with Staphylococcus species</p> Signup and view all the answers

    Which group of antibiotics is commonly considered in the combination therapy for endocarditis caused by Streptococcus Group D?

    <p>Aminoglycosides and beta-lactams</p> Signup and view all the answers

    Which organism is correctly identified as producing a red pigment?

    <p>Serratia</p> Signup and view all the answers

    Which characteristic distinguishes Streptococcus pneumoniae from other Streptococci?

    <p>Optochin susceptibility</p> Signup and view all the answers

    What is the primary cause of gas gangrene?

    <p>Clostridium perfringens</p> Signup and view all the answers

    Which organism is resistant to novobiocin and is known to cause urinary tract infections?

    <p>Staphylococcus saprophyticus</p> Signup and view all the answers

    Which conclusion can be drawn about the presence of greater than 10 epithelial cells in a specimen?

    <p>The specimen is heavily contaminated with oral flora.</p> Signup and view all the answers

    What separates Staphylococcus from Streptococcus in terms of catalase activity?

    <p>Staphylococcus is catalase positive, while Streptococcus is negative.</p> Signup and view all the answers

    What characterizes Streptococcus viridans in terms of clinical significance?

    <p>Associated with subacute bacterial endocarditis</p> Signup and view all the answers

    Which biochemical test differentiates the two genera in question based on lysine production?

    <p>Lysine decarboxylase test</p> Signup and view all the answers

    Which bacterial species is identified by its 'racquet' or 'drumstick' shaped terminal endospores?

    <p>C. tetani</p> Signup and view all the answers

    Which of the following options is associated with the characteristic 'fishy' odor when mixed with KOH?

    <p>Gardnerella</p> Signup and view all the answers

    What type of media is C. difficile primarily grown on?

    <p>CCFA agar</p> Signup and view all the answers

    Which bacterial option grows well on blood agar?

    <p>N. meningitidis</p> Signup and view all the answers

    What is the primary production characteristic of a scotochromagen?

    <p>Produces pigments in the dark</p> Signup and view all the answers

    Which outcome is characteristic of overwhelming disseminated intravascular coagulation (DIC) caused by N. meningitidis?

    <p>Shock and adrenal gland destruction</p> Signup and view all the answers

    Which deaminase activity is associated with H2S production in relation to TSI?

    <p>H2S positive and urease positive</p> Signup and view all the answers

    Which option is a non-photochromagen that does not show hydrolysis of Tween 30?

    <p>C. freundi</p> Signup and view all the answers

    Study Notes

    Bacterial Growth Requirements

    • Temperature influences bacterial growth:
      • Psychrophiles thrive at low temperatures (optimum = 15°C).
      • Mesophiles prefer moderate temperatures (optimum = 37°C; most pathogens).
      • Thermophiles grow at high temperatures (optimum = 50-60°C).
    • Optimal pH levels:
      • Bacteria typically thrive at pH 6.5-7.5.
      • Fungi prefer pH 5.0-6.0.
    • Oxygen requirements vary:
      • Aerobes need oxygen to grow.
      • Facultative anaerobes can utilize oxygen but can survive without it.
      • Obligate anaerobes are harmed by oxygen.
      • Microaerophiles prefer lower oxygen levels than atmospheric concentration.
      • Capnophiles prefer higher CO2 concentrations.
      • Aerotolerant organisms do not require oxygen but are not harmed by it.

    Typical Incubation Conditions

    • Requires 5-10% CO2, achievable in incubators or candle jars.
    • Temperature needed is generally between 35-37°C.
    • Humidity levels should be maintained at 50-70%.

    Culture Media

    • Growth media must meet the specific needs of bacteria.
    • Agar, a polysaccharide from marine algae, is commonly used (melts at 100°C, solidifies at ~45°C).
    • Complex media are frequently used, containing peptones and extracts.
    • Anaerobic media includes reducing agents to eliminate dissolved oxygen.

    Sterilization and Inhibition Techniques

    • Heat denatures proteins:
      • Moist heat via autoclave (121°C, 15 psi for 15 minutes).
      • Dry heat methods like incineration and hot air ovens (170°C for 2 hours).
      • Pasteurization uses temperatures like 140°C for short durations.
    • Filtration removes microorganisms (pore size 0.22 µm - 0.45 µm).
    • Refrigeration slows microbial growth while desiccation maintains organism viability.
    • Hypertonic solutions (osmotic pressure) can result in plasmolysis.
    • Radiation can damage microbial DNA by forming hydroxyl radicals.
    • Disinfection methods include:
      • Phenols, halogens (iodine, chlorine), alcohols for microbial cell disruption.

    Antibiotics and Their Actions

    • β-lactams (e.g., penicillins, cephalosporins) inhibit cell wall synthesis.
    • Glycopeptides (e.g., vancomycin) are effective against Clostridium difficile and MRSA.
    • Aminoglycosides (e.g., gentamicin) inhibit protein synthesis but are ineffective against anaerobes.
    • Tetracyclines (e.g., doxycycline) target protein synthesis affecting bone and teeth development.
    • Chloramphenicol can cause aplastic anemia; it intervenes in protein synthesis.
    • Macrolides (e.g., erythromycin) affect 50S ribosomal subunits in protein synthesis.
    • Quinolones (e.g., ciprofloxacin) inhibit nucleic acid synthesis, particularly effective against certain aerobes.
    • Sulfa Drugs (e.g., sulfamethoxazole) serve as folic acid synthesis intermediates; used in combination with trimethoprim for enhanced efficacy.
    • Streptogramins and Oxazolidinones target protein synthesis, useful against resistant Gram-positive bacteria.

    Antimicrobial Therapy Principles

    • Narrow-spectrum antibiotics target specific groups, while broad-spectrum cover both Gram-positive and Gram-negative bacteria.
    • Selective toxicity ensures microbial destruction without harming host cells.
    • Antimicrobial action categorization:
      • Bactericidal: kills the bacteria outright.
      • Bacteriostatic: halts bacterial growth; dependency on host immune response for eradication.
    • Drug interactions can exhibit:
      • Synergism: combined effect greater than individual actions.
      • Antagonism: one drug diminishes the effect of another.

    Sterilization and Disinfection

    • Sterilization kills all microorganisms, including spores and viruses.
    • Disinfection inactivates or inhibits microorganisms but may not affect spores.
    • Autoclave example: 121°C at 15 psi for 15 minutes.
    • Other sterilization methods: Incineration and Filtration.

    Antibiotics and Their Actions

    • B-lactams (e.g., Penicillins, Cephalosporins): Inhibit cell wall synthesis.

      • Notable examples include Ceftriaxone and Imipenem.

    • Glycopeptides (e.g., Vancomycin): Target cell wall synthesis and are effective against Clostridium difficile and MRSA.

    • Aminoglycosides (e.g., Gentamicin, Tobramycin): Inhibit protein synthesis, specifically act on the 30S ribosomal subunit, not effective against anaerobes.

    • Tetracyclines (e.g., Tetracycline, Doxycycline): Also inhibit protein synthesis on the 30S subunit; may affect bone and teeth development in children.

    • Chloramphenicol: Inhibits protein synthesis on the 50S subunit and may cause aplastic anemia.

    • Macrolides (e.g., Erythromycin, Clindamycin): Act on the 50S ribosomal subunit; Clindamycin is used for Gram-positive and Gram-negative anaerobes.

    • Quinolones (e.g., Ciprofloxacin): Inhibit nucleic acid synthesis, effective against Pseudomonas aeruginosa and other aerobes.

    • Sulfa Drugs (Sulfonomides) (e.g., Sulfamethoxazole): Analogues of PABA, used for UTIs and enteric infections; often combined with trimethoprim.

    • Streptogramins (e.g., Quinupristin/dalfopristin): Inhibit protein synthesis; effective against vancomycin-resistant Enterococcus faecium.

    • Oxazolidinones (e.g., Linezolid): Inhibit protein synthesis; used for Gram-positive infections, resistant to other antibiotics.

    Antimicrobial Therapy Principles

    • Narrow spectrum: Target specific groups of bacteria.
    • Broad spectrum: Effective against both Gram-positive and Gram-negative bacteria.
    • Selective toxicity: Only targets microbes without harming host cells.
    • Bactericidal action: Kills bacteria without the need for host immune response.
    • Bacteriostatic action: Reversible inhibition; depends on the host's defenses for ultimate effectiveness.

    Susceptibility Testing

    • Kirby-Bauer Method: Disk diffusion test using Mueller-Hinton agar; determines antibiotic susceptibility.

      • Critical parameters include agar depth, pH, and incubation conditions.

    • Broth Methods:

      • MIC (Minimum Inhibitory Concentration): Lowest concentration preventing bacterial growth.
      • MBC (Minimum Bactericidal Concentration): Lowest concentration resulting in >99.9% killing.

    • E-test: Uses a strip with a gradient of antibiotic concentrations to determine MIC.

    • Automated AST: Includes systems such as BD Phoenix and Vitek for susceptibility testing.

    Extended Spectrum Beta-Lactamase (ESBL)

    • Enzymes provide resistance to extended-spectrum cephalosporins and monobactams.
    • Common in Escherichia and Klebsiella species.
    • Detection requires reporting all penicillin, cephalosporin, and aztreonam as resistant if ESBL is present.

    Sources of Error in Disk Diffusion Testing

    • Incorrect pH or nutrient deficiencies in the agar can lead to abnormal results.
    • Inoculum size and agar depth can significantly impact inhibition zone sizes.
    • Methicillin degradation in storage affects test reliability.

    Detection of Resistance

    • MRSA detected with a zone of ≤10 mm using an oxacillin disk.
    • Vancomycin-resistant Enterococci (VRE) and carbapenem-resistant Enterobacteriaceae (CRE) are significant clinical concerns.

    Media Types and Purposes

    • Routine Media is common and assesses general bacterial presence.
    • Blood Agar (BA) detects hemolytic reactions in most bacteria.
    • Phenylethyl Alcohol Agar (PEA) selects for Gram-positive cocci and certain anaerobic Gram-negative bacilli.
    • Columbia CNA Agar specifically selects for Gram-positive cocci.
    • Thayer-Martin Agar is used for culturing Neisseria gonorrhoeae and N. meningitidis.
    • CAMPY-Blood Agar is optimal for isolating Campylobacter sp..
    • Thiosulfate-Citrate-Bile Salts-Sucrose (TCBS) Agar identifies Vibrio sp..
    • Buffered Charcoal Yeast Extract (BCYE) Agar is cultured for Legionella sp..

    Special Media

    • Bordet-Gengou Agar isolates Bordetella pertussis.
    • Cystine-Glucose Agar is specific for Francisella tularensis.
    • Fletcher's Medium is used for Leptospira isolation.
    • Skirrow Agar is selective for Helicobacter pylori.
    • Loeffler's Medium is utilized for Corynebacterium diphtheriae.
    • Thiosulfate-Citrate-Bile Salts-Sucrose (TCBS) Agar is tailored for Vibrio sp.

    Anaerobic Media

    • Bacteroides Bile Esculin Agar (BBE) selects for Bacteroides fragilis group.
    • Kanamycin-Vancomycin Laked Blood Agar (KVLB) enhances pigment production of Bacteroides sp..
    • Cycloserine-Cefoxitin Fructose Agar (CCFA) is selective for Clostridium difficile.
    • CDC Anaerobic Blood Agar enriched with hemin, cystine, and vitamin K supports anaerobes.
    • Cooked or Chopped Meat Medium is used to culture anaerobes.

    Specimen Collection and Handling

    • Collect material directly from the infection site for accurate results.
    • Timing is critical; for example, collect blood for Salmonella typhi during the first week and stool in subsequent weeks.
    • Utilize appropriate collection devices to avoid contamination.
    • Avoid refrigerating spinal fluids, anaerobic specimens, or GC samples.
    • Collect samples before antibiotic therapy for optimal culture results.
    • Set up cultures within 2 hours post-collection to ensure viability.

    Criteria for Rejection

    • Avoid preservatives that can interfere with results.
    • Insufficient sample quantity or dry swabs are unacceptable.
    • Leaky containers may lead to contamination and pose biohazard risks.

    Blood Culture Collection

    • Prep skin with alcohol (70%) and iodine to reduce contamination.
    • Ideal time to draw blood is prior to fever spikes.
    • Limit to 2-3 cultures in a 24-hour period to prevent overflow.
    • Utilize an antibiotic removal device if the patient is on antibiotics.
    • Ideal blood-to-broth dilution ratio is 1:10, with a minimum of 10 ml for adults.

    Culture Conditions

    • Most media incubated at 35-37°C, with exceptions for Campylobacter (42°C) and Yersinia (25-30°C).
    • Maintain anaerobic conditions using media like thioglycollate.
    • Utilize gas pak jars or anaerobic chambers for optimal growth.

    Microscopy Techniques

    • Light Microscopy offers resolving power of 0.2 µm, using ocular and oil immersion lenses.
    • Darkfield Microscopy highlights spirochetes via reflected light.
    • Fluorescence Microscopy employs stains like auramine-rhodamine for enhanced visualization.
    • Electron Microscopy achieves high-resolution imaging, effective for viral identification.

    Specimen Collection and Handling

    • Collect material from the infection site promptly.
    • Optimal timing for specific cultures, e.g., Salmonella typhi: blood in the first week, stool in the second and third weeks.
    • Use appropriate collection devices for different specimens.
    • Do not refrigerate spinal fluids, anaerobic, or gonococcal specimens.
    • Collect specimens before the initiation of antibiotic therapy.
    • Set up cultures within two hours of collection to ensure viability.

    Criteria for Rejection of Specimens

    • Presence of preservatives in collected samples.
    • Insufficient specimen quantity impacts diagnostic utility.
    • Dry swabs will not yield viable organisms.
    • Leaky containers may lead to contamination and pose biohazard risks.

    Blood Culture Collection

    • Prep the skin with 70% alcohol and iodine before collection.
    • Best to draw blood cultures right before fever spikes for accurate results.
    • At least two cultures should be collected, but limit to three within a 24-hour window.
    • Utilize antibiotic removal devices (ARD) if the patient is on antibiotics.
    • Isolator® systems are most effective for fungi and acid-fast organisms.
    • Blood should be diluted at a ratio of 1:10 into broth; for adults, collect at least 10 mL.

    Culture Conditions

    • Most plates incubate at 35-37°C; Campylobacter requires 42°C, Yersinia between 25-30°C.
    • Maintain anaerobic conditions using broths with thioglycollate or cysteine and gas pak systems.
    • Media types include non-selective (blood agar) and selective (EMB, MAC) which inhibit certain organisms.

    Inoculation Techniques

    • Use nichrome or platinum loops for streaking to isolate cultures.
    • Employ calibrated loops for urine colony counts, with a standard reading after 18-24 hours.

    Common Stains in Microbiology

    • Gram Stain: Crystal Violet, decolorized with alcohol/acetone, counterstained with Safranin; identifies gram-positive (purple) and gram-negative (pink) organisms.
    • Kinyoun & Ziehl-Nielson Stains: Used for mycobacteria, pink results indicate acid-fast organisms.
    • Auramine-Rhodamine Stain: Fluorescent stain for mycobacteria with an orange color indicating positive results.
    • Calcofluor White Stain: Identifies yeast and fungi; produces a bluish-white fluorescence when combined with 10% KOH.

    Gram Positive Cocci - Staphylococcus

    • Staphylococcus forms "grape-like" clusters; common pathogen includes Staphylococcus aureus.
    • S. aureus: Coagulase positive; causes furuncles, impetigo, and post-surgical infections.
    • Incidence of intoxications like toxic shock syndrome and food poisoning are notable.
    • Resistant strains (MRSA) pose challenges; vancomycin is the treatment of choice.
    • Coagulase Negative Staphylococcus: Opportunistic infections in immunocompromised individuals and those with prosthetic devices.

    Resistance and Susceptibility

    • Staphylococcus is often resistant to penicillin due to plasmid-mediated β-lactamase production.
    • Susceptibility to penicillinase-resistant penicillins (e.g., methicillin) can vary among strains.

    Inoculation Techniques

    • Streak for isolation using nichrome, platinum, or disposable loops.
    • Use calibrated loops (0.01 ml or 0.001 ml for urine colony count plates).
    • For colony counting: Multiply the number of colonies by 100 for a 0.01 ml loop or by 1000 for a 0.001 ml loop.
    • Read and report results after 18-24 hours.

    Common Stains in Microbiology/Mycobacteriology

    • Gram Stain

      • Primary: Crystal Violet
      • Decolorizer: Alcohol/Acetone
      • Counterstain: Safranin
      • Results: Positive (Purple), Negative (Pink)
      • Principle: Iodine mordant forms a complex with violet dye; washes out from gram-negative cells.

    • Kinyoun & Ziehl-Nielsen Stain

      • Primary: Carbol Fuchsin
      • Decolorizer: Acid Alcohol
      • Counterstain: Methylene Blue
      • Results: Positive (Pink), Negative (Blue)
      • Principle: Specifically for Mycobacteria.

    • Auramine-Rhodamine Stain

      • Primary: Auramine and Rhodamine
      • Decolorizer: Acid Alcohol
      • Counterstain: Potassium Permanganate
      • Results: Positive (Orange), Negative (No Fluorescence)
      • Principle: Quick detection of Mycobacteria.

    Catalase and Coagulase Tests

    • Catalase Test: H2O2 breaks down to water and oxygen; positive results show bubbling (Staphylococcus positive, Streptococcus negative).
    • Coagulase Test: Detects coagulase and Protein A; determines Staphylococcus aureus from other staphylococci.

    Staphylococcus (Catalase Positive)

    • S. aureus

      • Coagulase Positive
      • Associated Infections: Carbuncles, furuncles, paronychia, and bacteremia.
      • Intoxications: Scalded Skin Syndrome, Toxic Shock Syndrome, Gastritis (enterotoxin).
      • Characteristics: Most beta-lactamase producers; many are MRSA (Methicillin-resistant).

    • S. epidermidis

      • Coagulase Negative
      • Associated Infections: Endocarditis, prosthetic device infections.
      • Characteristics: Most are methicillin-resistant; sensitive to novobiocin.

    • S. saprophyticus

      • Coagulase Negative
      • Associated Infections: Urinary Tract Infections (UTIs) in young women.
      • Characteristics: Resistant to novobiocin.

    Streptococcus Overview

    • Spherical or oval bacteria; can form chains or pairs.

    • Lancefield classification based on specific carbohydrate characteristics.

    • S. pyogenes (Group A)

      • Beta hemolytic.
      • Produces Streptolysin S (stable) and Streptolysin O (oxygen-labile).
      • Causes scarlet fever rash due to erythrogenic toxin.

    • Enterococcus

      • Grows on bile esculin medium (BEM) and in 6.5% NaCl.
      • Associated Infections: UTIs, bacteremia.

    • S. pneumoniae

      • Alpha hemolytic. Characterized by crater-like colonies.
      • Associated Infections: Primary lobar pneumonia, meningitis, bacteremia.
      • Laboratory Diagnosis: Quellung reaction and sensitivity to optochin; bile soluble.

    Other Notable Streptococci

    • S. viridans
      • Associated with subacute bacterial endocarditis; typically alpha hemolytic.

    Key Points for Practitioners

    • Perform daily quality control (QC) tests for reliable results.
    • Wash hands and wear lab coats to prevent contamination.
    • Remember the key morphology and biochemical characteristics for accurate identification and diagnosis.

    Gram Negative Cocci

    • Neisseria and Moraxella are key genera characterized as diplococci (kidney bean shape) and oxidase positive.
    • Neisseria gonorrhoeae:
      • Grows on chocolate and Thayer-Martin agar requiring 5-10% CO2; may take up to 48 hours for growth.
      • Ferments glucose and is associated with gonorrhea, often asymptomatic and commonly mixed with Chlamydia.
      • Gram stain is sensitive in males but not in females.
    • Moraxella catarrhalis:
      • Causes respiratory infections, grows well on chocolate and blood agar but not on MacConkey's agar.
      • Colonies are hard, motile, asaccharolytic, and usually beta-lactamase positive.

    Acinetobacter Species

    • Emerging pathogen causing respiratory infections, UTIs, or acts as a colonizer.
    • Appears as a coccobacillus and displays resistance to many drugs requiring antibiotic susceptibility testing.
    • Can cause neonatal meningitis and sepsis.

    Gram Positive Rods

    • Corynebacterium:
      • Catalase positive and displays a "Chinese letter" arrangement; metachromatic granules may be observed.
      • Growth on Loeffler's slants and capable of Tellurite hydrolysis.
      • Toxin production is determined by the Elek test.
    • Listeria:
      • Catalase positive with tumbling motility at 25°C; may cause neonatal meningitis and sepsis.
      • Can survive in cold conditions (cold enrichment).
    • Erysipelothrix:
      • Catalase negative, associated with infections in fishermen, butchers, and veterinarians.
      • Demonstrates "test tube brush" growth in gelatin.

    Bacillus Species

    • Bacillus species are spore formers, catalase positive, with "ground glass" hemolytic colonies.
    • Capable of producing exotoxins and linked with bacillary dysentery.

    Escherichia coli

    • Most common cause of UTIs in females and responsible for various intestinal infections.
    • Key characteristics include being indole and lactose positive with IMViC reactions of ++--.
    • Types of pathogenic E. coli:
      • Enterotoxigenic (ETEC) produces heat labile (LT) and heat stable (ST) toxins.
      • Enteroinvasive (EIEC) penetrates epithelial cells of the large intestine, may be lactose negative.
      • Enterohemorrhagic (EHEC), notably O157:H7, causes severe illness with Shiga-like toxin production.

    Shigella

    • Comprised of four groups:
      • S. dysenteriae (Group A, most severe),
      • S. flexneri (Group B),
      • S. boydii (Group C),
      • S. sonnei (Group D, most common in the US).

    Common Gram Negative Selective Media

    • MacConkey Agar differentiates lactose fermenters (dark pink) from non-fermenters (transparent).
    • Eosin Methylene Blue (EMB) agar indicates lactose fermentation with green sheen.
    • Hektoen-Enteric (HE) agar and Salmonella-Shigella (SS) agar differentiate species based on H2S production and lactose fermentation.

    Enterobacteriaceae: Primary Differentiating Tests

    • Triple Sugar Iron (TSI) tests indicate fermentation patterns.
    • Various biochemical tests assess urease, VP, and motility to differentiate genera.
    • Notable reactions include oxidase tests and ONPG tests to detect beta-galactosidase.

    Salmonella

    • Requires a large inoculum for infection (>100,000).
    • Key biochemical characteristics include H2S positive and lysine positive reactions.
    • S. enterica has over 2000 serotypes, including pathogenic strains leading to typhoid fever and septicemia.

    Biochemical Tests Summary

    • Oxidase test: positive = purple; Nitrate test: positive = pink.
    • TSI slant can provide a complete metabolic profile for identification of bacteria.

    Key Reminders

    • Differentiate bacteria based on catalase, H2S, and hemolytic activity.
    • Recognize the importance of resistance patterns in emerging pathogens like Acinetobacter.
    • Klebsiella is an opportunistic pathogen commonly associated with urinary tract infections (UTIs) and pneumonia; often resistant to ampicillin.
    • Characterized as non-motile, encapsulated, with variable urease activity, VP positive, and negative for ornithine.
    • Notably includes Klebsiella granulomatis, previously known as Calymmatobacterium granulomatis, linked to sexually transmitted infections (STIs).
    • Citrobacter is an opportunistic pathogen, lysine negative, and biochemically similar to Salmonella.
    • Enterobacter species are motile and positive for ornithine, distinguishing them from Klebsiella.
    • Serratia can produce red pigment and is positive for DNase and gelatinase.

    Key Characteristics of Proteus Species

    • Proteus mirabilis is highly sensitive to penicillins and indole negative.
    • Proteus vulgaris is indole positive and produces hydrogen sulfide (H2S).
    • Both species exhibit urea positive activity, which aids in their identification.

    Yersinia Characteristics

    • Yersinia enterocolitica grows optimally at room temperature with cold enrichment, known for being invasive and toxigenic.
    • Yersinia pseudotuberculosis causes acute mesenteric lymphadenitis and resembles true tuberculosis.
    • Yersinia arizonae tests positive for ONPG and ferments glucose with characteristic fermentation patterns on KIA media.

    Biochemical Tests

    • Kligler Iron Agar (KIA) distinguishes carbohydrate fermentation; no sucrose is present unlike TSI.
    • Citrate test utilizes green media, turning blue for positive results indicating citrate utilization.
    • Decarboxylase tests measure the ability to decarboxylate amino acids, with lysine, ornithine, and arginine indicators.
    • Indole test indicates the presence of tryptophan breakdown; Kovac's reagent turns pink if positive.

    Various Tests and Indicators

    • Voges-Proskauer (VP) test detects acetylmethylcarbinol (acetoin); a pink color indicates a positive result.
    • Urease test measures the breakdown of urea into ammonia and CO2, indicated by a pink phenol red color change.
    • TSI test reactions use a mnemonic for visualization of results, distinguishing between acid and alkaline reactions.
    • Pigment production can be tested with ferric chloride for phenylalanine deaminase, positive reaction yielding a green color.

    Gram-Negative Non-Fermenters

    • Oxidase-positive organisms often show weakly positive results or exceptions.
    • Rarely grow on MacConkey's agar, do not ferment glucose, resulting in alkaline/alkaline reaction (alk/alk).
    • Pseudomonas aeruginosa is a common pathogen, oxidase positive, and typically does not utilize lactose.
    • Burkholderia cepacia is a polymyxin B-resistant opportunistic pathogen particularly concerning patients with cystic fibrosis.

    Gram-Negative Oxidase Positive Fermenters

    • Vibrio Characteristics
      • Curved rod-shaped bacteria with polar flagella
      • Selectively cultured on Thiosulfate-Citrate-Bile Salts-Sucrose (TCBS) agar
      • Blood Agar Plate (BAP) shows hemolytic colonies
      • Lactose negative, differentiating them from enteric bacteria
      • Nitrate reduction test: positive (NO3 to NO2)

    Vibrio cholerae (Serogroup 01)

    • Causes rapid onset gastroenteritis within 3-10 hours
    • Results in profuse diarrhea often described as "rice water" stools, with mucus flecks
    • Requires a high concentration of organisms for infection unless the host is hypochlorohydric
    • Appears yellow on TCBS agar

    Vibrio parahemolyticus

    • Appears green on TCBS
    • Associated with enteritis, often from consuming contaminated seafood

    Vibrio vulnificus

    • Also appears green on TCBS
    • Can cause wound infections and other severe diseases, particularly in immunocompromised individuals

    Aeromonas

    • Motile with polar flagella, resembling Vibrio
    • Majority are indole positive, differentiating them from other pathogens
    • Capable of growing on MacConkey agar (MAC)
    • Causes cellulitis, wound infections, and diarrhea

    Other Organisms

    • Campylobacter jejuni
      • Small, curved rods with a "seagull" appearance
      • Microaerophilic, takes 2-4 days for growth
      • Cultured on CAMPY agar
      • Linked to raw poultry and contaminated water, similar to Salmonella
      • Treatment usually involves erythromycin or tetracycline
      • Biochemical characteristics include:
        • Catalase positive
        • Oxidase positive
        • Hippurate positive

    Zoonotic Diseases Overview

    • Zoonotic diseases are infections that can be acquired directly or indirectly from animals to humans.

    Brucella

    • Gram-negative coccobacilli associated with brucellosis.
    • Blood culture is positive within the first two weeks; cultures should be held for 21 days.
    • Different species have varying features:
      • B. abortus (cows): H2S positive, thionine positive, basic fuchsin negative.
      • B. suis (pigs): H2S variable, thionine negative, basic fuchsin positive.
      • B. melitensis (goats): H2S negative, thionine negative, basic fuchsin negative.
    • Mnemonic: "Cows eat Thionine. Pigs eat Basic Fuchsin. Goats eat neither."

    Francisella tularensis

    • Faintly staining gram-negative coccobacillus that causes tularemia, also known as "rabbit fever."
    • Infection through tick bites, posing a high risk to laboratory personnel.
    • Characterized by tiny pinpoint colonies, requiring cystine-glucose media for growth.
    • Tests positive for H2S using lead acetate.
    • Operates under biosafety level 3 due to its infectious potential.

    Yersinia pestis

    • Gram-negative bacterium responsible for plague.
    • Notable for bi-polar staining, resembling a safety pin under microscope.
    • Transmitted primarily by fleas, rats, and other mammal reservoirs.
    • Managed at biosafety level 3 due to its pathogenicity.

    Pasteurella multocida

    • Gram-negative rod associated with infections from cat and dog bites.
    • Exhibits a "mousy" odor and demonstrates bi-polar staining.
    • Oxidase and indole positive, indicating specific biochemical reactions.
    • Ferments glucose and sucrose, useful for identification.
    • Operates under biosafety level 2 precautions.

    Streptobacillus moniliformis

    • Long filamentous gram-negative rods presenting a pleomorphic shape with "puffball" or "string of pearls" colonies in thioglycolate broth.
    • Causes "rat bite fever" and Haverhill fever, infections resulting from contact with infected species.
    • Ascitic fluid sample is necessary for diagnosis; sodium polyanethol sulfonate (SPS) inhibits growth of other bacteria in cultures.

    Bacterial Growth Requirements and Culture Techniques

    • Red blood cells need heat to break down and release necessary growth factors (X and V factors).
    • Special media is required for certain bacteria; common media includes:
      • Chocolate Agar: Used for growth of fastidious organisms.
      • Bordet-Gengou: Contains potato infusion with glycerol and 20% sheep red blood cells.
      • Regan/Lowe: Oxoid charcoal agar with 10% horse blood; has a longer shelf life than other media.
    • Satellitism: Phenomenon where Haemophilus species grow in the hemolytic zone surrounding S. aureus colonies, as S. aureus produces V factor and hemolyzes blood to release X factor.

    Infections Caused by Haemophilus Species

    • Meningitis in children predominantly affects 2-4 year-olds, usually preceded by nasopharyngeal colonization.
    • Classic symptoms and diagnosis often involve blood culture over throat cultures, especially in epiglottitis cases in children.

    Characteristics of HACEK Group

    • Aggregatibacter aphrophilus: Associated with endocarditis, weakly oxidase-positive, indole negative.
    • Aggregatibacter actinomycetemcomitans: Linked to periodontal and jaw abscesses; shows distinctive colony morphology in plaque.
    • Cardiobacterium hominis: Can cause endocarditis and may result in false positive Gram reactions; oxidase positive, indole positive.
    • Eikenella corrodens: Notable for its "bleachy" odor and pitting of agar; involved in periodontal infections.
    • Kingella kingae: Causes septic arthritis and osteomyelitis primarily in children; presents with corroding colony appearance.

    Mycoplasma and Ureaplasma

    • Mycoplasma are the smallest free-living microorganisms, lacking a cell wall, making them resistant to Gram staining.
    • M. pneumoniae is known for causing atypical pneumonia ("walking pneumonia") and leads to a positive cold agglutinin titer.
    • Ureaplasma urealyticum is associated with non-gonococcal urethritis and urease production; treated with tetracycline or spectinomycin.
    • M. hominis can colonize the genitourinary tract and is linked to postpartum fever.

    Legionella pneumophila

    • Causes Legionnaires' disease, a severe form of pneumonia; milder form called Pontiac fever.
    • L. pneumophila serogroups 1 and 6 account for approximately 75% of cases.
    • Found in potable water and faulty air conditioning systems.
    • Identification relies on sputum, bronchial washings, or pleural fluid; Dienes stain used for specificity.

    Anaerobic Infections

    • Indicators of anaerobic infections include foul odor, close proximity to mucosal surfaces, and previous antibiotic therapy.
    • Culture techniques include:
      • Classic anaerobic culture using Gas Pak jars with palladium pellets for hydrogen generation.
      • Methylene blue or resazurin act as indicators in cultures, changing color based on oxidation state.

    Gram-Negative Anaerobes

    • Fusobacterium nucleatum: Characterized by spear-shaped, gram-negative slender fusiforms, and shows bread crumb or speckled colonies at 36°C in anaerobic conditions.
    • Bacteroides fragilis: Produces dark colonies greater than 1 mm on BBE and catalase positive. May fluoresce brick-red and is commonly found in polymicrobial infections.
    • Resistance Susceptibility Testing: Notable resistance patterns include Bacteroides fragilis resistant to vancomycin and sensitive to kanamycin, while Fusobacterium genera show variable reactions.

    Gram-Positive Anaerobes

    • Clostridium difficile: Associated with Pseudomembranous Colitis (PMC) and recognized by the 'horse stable' odor on CCFA agar; known for emerging resistant strains.
    • Clostridium perfringens: Exhibits a double zone of hemolysis and is a well-known cause of gas gangrene and food poisoning, though spores are seldom observed.
    • Clostridium tetani: Notable for terminal spores shaped like racquets and is the causative agent of tetanus.

    Actinomyces

    • Actinomyces israelli: Identified by "molar tooth" colonies, branching gram-positive rods, and linked with lumpy jaw; associated with sulfur granules.

    Treponema and Leptospira

    • Treponema pallidum: Causes syphilis, with lesions appearing 2-10 weeks post-infection; chancre heals without treatment.
    • Leptospira: Hooked spirals that are animal pathogens spread through contaminated water; darkfield microscopy useful for diagnosis, culturable in Fletcher’s media.

    Chlamydia

    • Chlamydia trachomatis: An obligate intracellular parasite responsible for sexually transmitted infections, treated with penicillin or tetracycline; diagnosed through Giemsa stain.

    Borrelia

    • Borrelia recurrentis: Known for "relapsing fever," transmitted by ticks or lice, characterized by looser coils visible under Giemsa or Wright's stain, and capable of relapsing due to antigenic variation.

    Rickettsial Infections

    • Infection vectors and notable Rickettsiae include:
      • Coxiella burnetti: Transmitted via inhalation; confirmed with Complement Fixation Test.
      • Rickettsia rickettsii: Transmitted by ticks; characterized by a rash on palms and soles.
      • Rickettsia typhi: Flea-borne and associated with murine typhus.

    Mycobacteria

    • Mycobacteria Characteristics: Slim, gram-variable rods resistant to normal staining due to high lipid content; distinguished through acid-fast staining techniques such as Ziehl-Neelsen and Kinyoun stains.
    • Growth and Culture:
      • Optimal growth conditions include incubation at around 30-36°C and can take 3-6 weeks for visibility; special media like Lowenstein-Jensen and Tween 80 may be employed for enhanced growth.

    Specimen Collection Guidelines

    • Recommended specimens include sputum (three consecutive mornings), bronchial washings, and urine; must be collected sterilely and stored properly to prevent contamination.

    Rickettsiae

    • Small gram-negative coccobacilli, obligate intracellular parasites.
    • Transmitted primarily by arthropod vectors (insects).
    • Common symptoms include fever, headache, and rash; notable exception is Q fever which presents without a rash.
    • Best visualized using Giemsa stain.
    • Weil-Felix test detects Rickettsial antibodies using Proteus serotypes OX-19, OX-2, and OX-K; a titer of 1:160 or a four-fold rise indicates infection.

    Common Rickettsiae and Associated Vectors

    • Rickettsial Pox (R. akari): spread by house mites; no Proteus reactions.
    • Q Fever (Coxiella burnetti): airborne transmission; confirmed via complement fixation test.
    • Typhus Fever (R. prowazekii): transmitted by lice; positive for OX-19, variable for OX-2.
    • Rocky Mountain Spotted Fever (R. rickettsiae): ticks as vectors; characterized by rash on palms and soles; positive for OX-19 and OX-2.
    • Murine Typhus (R. typhi): transmitted by rat fleas; positive for OX-19 and OX-2.

    Mycobacteria

    • Slim, gram-variable rods with high lipid content, resulting in poor Gram staining.
    • Staining methods include Ziehl-Neilsen (hot) and Kinyoun (cold) acid-fast stains; Auramine-Rhodamine for fluorescent microscopy.
    • Cultivation requires specific conditions: Lowenstein-Jensen media, temperature at 36°C (some at 30°C), and takes 3-6 weeks for growth.
    • Automated cultures can expedite growth and testing for antibiotic susceptibility.
    • Significant pathogen: Mycobacterium avium complex, associated with pulmonary and disseminated disease, especially in immunocompromised patients.

    Mycobacterium Leprae

    • Etiological agent of leprosy (Hansen disease), affects skin, mucous membranes, and nerves.
    • Characterized by progressive disease manageable with treatment.
    • Optimal growth in the footpads of armadillos.

    Differentiating Mycobacteria

    • Notable characteristics for identifying species: niacin production, nitrate reduction, Tween 80 hydrolysis, and tellurite utilization.
    • Mycobacterium tuberculosis: rapid grower and positive for key biochemical reactions; forms a distinct identification profile.

    Specimen Collection and Pathogen Association

    • Throat/Oropharynx: normal flora includes alpha-streptococci; pathogens can be Group A Streptococcus and Neisseria meningitidis, especially in children.
    • Deep Wounds/Abscesses: typically contain anaerobes and aerobes; collection methods should bypass normal flora.
    • Superficial Wounds: often colonized by Staphylococcus aureus and Streptococcus Group A.
    • Blood: typically sterile; any organism found in immunocompromised individuals or those with prosthetic heart devices is seen as pathogenic.
    • Peptic Ulcers: associated organisms vary; specimen collection may involve NP swabbing procedures.

    Virology Overview

    • Viruses contain either RNA or DNA, but not both; they lack structural elements for protein synthesis and replicate exclusively within host cells.
    • Viral specimens, including pre- and post-convalescent sera, should be shipped on dry ice.
    • Specimens for viral culture require transport media enriched with nutrients (such as fetal calf serum or albumin) and antibiotics.

    Laboratory Methods

    • Enzyme Immunoassay (EIA) detects viral antibodies or antigens, like HBsAg and anti-HBsAb.
    • Viral culture methods assess live virus presence.
    • Electron microscopy allows visualization of viral particles.
    • Molecular techniques include DNA probes and Polymerase Chain Reaction (PCR):
      • PCR amplifies nucleic acid sequences in cycles, doubling the target each time.

    RNA Viruses and Associated Diseases

    • Flavivirus: Causes Yellow Fever, Dengue, and St. Louis Encephalitis; primarily transmitted by mosquitoes.
    • Hantavirus: Linked to Pulmonary Syndrome and Hemorrhagic Fever; transmitted by rodents.
    • Hepatitis A Virus (HAV): Causes Hepatitis A; commonly associated with shellfish; among the most stable viruses infecting humans.
    • Hepatitis C Virus (HCV): Previously known as non-A, non-B hepatitis; causes Hepatitis C.
    • Influenzavirus: Responsible for influenza outbreaks.
    • Morbillivirus: Causes measles; more severe in adults.
    • Mumps Virus: Causes mumps.
    • Poliovirus: Leads to poliomyelitis and aseptic meningitis; naturally infects only humans.
    • Respiratory Syncytial Virus (RSV): Causes serious respiratory infections in young children, leading to giant multinucleated cells.
    • Rhabdovirus: Causes rabies; identified by Negri bodies in the brain; wildlife is a reservoir.
    • Rhinovirus: Common cause of the cold.
    • Rotavirus: Causes acute infantile diarrhea, potential fatality in infants.
    • Rubivirus: Causes rubella; linked to serious congenital abnormalities; vaccination available but contraindicated during pregnancy.

    Retroviruses and Associated Diseases

    • Human Immunodeficiency Virus (HIV): Causes AIDS; detected via EIA, confirmed by Western Blot.
    • Human T-Cell Leukemia Virus (HTLV-I): Causes T-cell leukemia and tropical spastic paraparesis; confirmed by EIA techniques.
    • Human T-Cell Leukemia Virus (HTLV-II): Associated with hairy-cell leukemia; confirmed by EIA.

    DNA Viruses and Associated Diseases

    • Adenovirus: Common cause of respiratory infections.
    • Cytomegalovirus (CMV): Primary viral cause of mental retardation; significant risk for immunocompromised patients.
    • Epstein-Barr Virus (EBV): Causes infectious mononucleosis and chronic fatigue syndrome; associated with Burkitt's lymphoma.
    • Hepatitis B Virus (HBV): Causes Hepatitis B; detectable via ELISA; vaccination available.
    • Herpesviruses: Includes HSV-1 (oral infections) and HSV-2 (genital infections).
    • Human Papillomavirus (HPV): Causes genital and cutaneous warts; some types associated with cervical carcinoma; vaccine available.
    • Poxvirus: Smallpox, eradicated in the general population but noted for lab outbreaks.
    • Varicella-Zoster Virus: Causes chickenpox in children and shingles in adults; diagnosis based on clinical observation.

    Important Notes

    • Recognize that viruses are non-cellular entities that reproduce only in host cells, consisting of nucleic acid enveloped in a protein coat.
    • Evaluate laboratory results carefully to distinguish viral diseases and assess disease association, notably Negri bodies in rabies diagnoses.

    Microbiology Sample Questions

    • "Rice water stool" is linked to Vibrio cholerae infections.
    • Bluish purulent lesions with a gram-negative, motile rod suggest Pseudomonas aeruginosa.
    • Small gram-negative rods in genital soft chancre indicate a possible infection by Haemophilus ducreyi.
    • Phenomenon of alpha hemolysin observed on blood agar often relates to Streptococcus pneumoniae.
    • Lysine decarboxylase production differentiates Citrobacter from Salmonella.
    • Autoclave sterilization requires 15 psi, at 121 °C for 15 minutes.
    • Clinical rabies diagnosis relies on the observation of Negri bodies in brain tissue.
    • Catalase positive, coagulase negative gram-positive cocci suggest Staphylococcus saprophyticus in suspected UTI specimens.
    • Gardnerella vaginalis is associated with a "fishy" odor when mixed with KOH, indicating bacterial vaginosis.

    Gram Stain and Biochemical Tests

    • A sputum specimen showing gram-positive cocci in chains may suggest Streptococcus pneumoniae, confirmed via optochin susceptibility.
    • Serratia marcescens is recognized for producing a red non-water soluble pigment.
    • For urinary tract infections, the presence of > 10 epithelial cells indicates specimen contamination.
    • Campylobacter jejuni demonstrates oxidase positivity and optimal growth at 42 °C.

    Specific Pathogens and Media

    • Loeffler’s medium is optimal for isolating Corynebacterium diphtheriae.
    • The drug of choice for methicillin-resistant Staphylococcus infections is vancomycin.
    • Clostridium perfringens is linked to gas gangrene, identifiable by its stormy fermentation.
    • Photochromogenic mycobacterium isolated at 30 °C is likely Mycobacterium marinum.
    • Ebola virus causes hemorrhagic fever, while HIV is responsible for AIDS, and rabies virus presents differently.

    Diagnosis and Clinical Presentation

    • Endocarditis due to Streptococcus Group D necessitates a synergistic relationship between penicillin and aminoglycosides.
    • Gram variable rods in a wet prep from a patient with vaginitis indicate a possible Gardnerella vaginalis infection.
    • Diagnosis of Clostridium difficile requires examination of CCFA agar, while C. tetani displays "drumstick" shaped endospores.
    • Textural differences in TSI (triple sugar iron) can help identify unknown organisms, particularly H2S production.

    Additional Notes

    • Endotoxins from Neisseria meningitidis can lead to DIC (disseminated intravascular coagulation) and adrenal gland destruction.
    • Mycobacterium xenopi is a non-photochromogenic organism grown typically at 37 °C.
    • The specimen of choice for epiglottitis is collected via spinal fluid analysis.

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