Bacterial Classification and Characteristics
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Questions and Answers

Which organism is characterized by producing ammonia as a rapid urease producer?

  • Enterobacter
  • Proteus (correct)
  • Klebsiella
  • Citrobacter

    • Which of these organisms is linked to bloody diarrhea due to the Shiga-like toxin?

  • Enterobacter
  • Serratia
  • Escherichia (correct)
  • E.coli (EAEC)

    • What is the expected reaction of Citrobacter in a TSI test?

  • K/A G H2S (-)
  • A/A G H2S (+) (correct)
  • A/A G H2S (-)
  • K/K

    • Which organism is known for causing persistent watery diarrhea?

    <p>Enteroaggregative E.coli (EAEC)</p> Signup and view all the answers

    In the LIA test, what indicates a positive result?

    <p>Green color develops on slant</p> Signup and view all the answers

    Which of the following bacteria is non-motile at 37°C?

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

    Which organism is characterized as a lactose fermenter producing a green metallic sheen on Eosin Methylene Blue agar?

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

    Which of the following is not a gas producer?

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

    Which organism is positive for H2S production?

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

    Which of these bacteria is classified as an oxidase positive organism?

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

    Which bacteria are non-fermenters, characterized by colorless colonies?

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

    Which medium is used to enhance enteric bacteria in culture?

    <p>Gram negative broth</p> Signup and view all the answers

    Which of these organisms is a non-lactose fermenter that produces pink colonies?

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

    What is the primary habitat for Plesiomonas?

    <p>Domestic environments</p> Signup and view all the answers

    Which organism is characterized by a 'grape-like or corn tortilla-like' odor?

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

    What distinguishes Aeromonas from other Pseudomonas species?

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

    Which of the following statements is true regarding Vibrio mimicus?

    <p>It is associated with gastroenteritis.</p> Signup and view all the answers

    What is the classification of Pseudomonas aeruginosa?

    <p>Obligate aerobe</p> Signup and view all the answers

    Which characteristic is NOT associated with Aeromonas hydrophilia?

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

    What type of hemolysis is observed with Plesiomonas on blood agar?

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

    Which organism is identified by its non-halophilic nature?

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

    Which of the following statements is true about facultative anaerobes?

    <p>They can grow in both the presence and absence of oxygen.</p> Signup and view all the answers

    Which organism is catalase positive?

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

    What characterizes the fermentation of glucose by these organisms?

    <p>They are glucose fermenters.</p> Signup and view all the answers

    What type of colonies do lactose fermenters produce on MacConkey agar?

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

    Which antigen is primarily heat stable?

    <p>O Antigen</p> Signup and view all the answers

    Which of the following are selective agars for laboratory diagnosis?

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

    Which statement accurately describes the flagella of most facultative anaerobes?

    <p>They are motile with peritrichous flagella.</p> Signup and view all the answers

    Which organism is primarily associated with non-lactose fermentation?

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

    What is the optimal temperature for the growth of Campylobacter species?

    <p>42 - 43 C</p> Signup and view all the answers

    Which of the following is NOT a virulence factor of Chromobacterium violaceum?

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

    Which characteristic is shared by both Chromobacterium violaceum and Campylobacter?

    <p>Microaerophilic nature</p> Signup and view all the answers

    What type of infections is Campylobacter primarily associated with?

    <p>Gastrointestinal infections</p> Signup and view all the answers

    Which morphological feature helps differentiate Campylobacter from other enteric bacteria?

    <p>Curved or seagull-winged rods</p> Signup and view all the answers

    What is the primary method used for culturing Campylobacter species?

    <p>Campy-BAP or Skirrow's medium</p> Signup and view all the answers

    What type of motility is exhibited by Campylobacter species?

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

    What type of infections can Chromobacterium violaceum cause in intravenous drug users?

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

    What characteristic distinguishes Burkholderia pseudomallei in Gram stain preparations?

    <p>Bipolar staining resembling a safety pin</p> Signup and view all the answers

    What environment does Burkholderia cepacia typically thrive in?

    <p>Soil, water, and plants</p> Signup and view all the answers

    Which of the following symptoms is associated with Burkholderia mallei infection?

    <p>Glanders in horses and cattle</p> Signup and view all the answers

    Which of the following best describes the cultural characteristics of Burkholderia pseudomallei on Ashdown media?

    <p>Wrinkled and deep pink colonies</p> Signup and view all the answers

    What is a notable feature of Haemophilus species?

    <p>Nonmotile and facultative anaerobic</p> Signup and view all the answers

    What clinical complication is associated with Burkholderia cepacia in cystic fibrosis patients?

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

    Which of the following is a common odor associated with Burkholderia pseudomallei colonies?

    <p>Earthy odor</p> Signup and view all the answers

    What is the primary growth temperature for Campylobacter jejuni?

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

    Study Notes

    Bacterial Classification and Characteristics

    • Gram-negative cocci: Includes Neisseria and Moraxella. Characterized by oxidase-positive and gram-negative diplococci. These bacteria are capnophilic, meaning they prefer environments with carbon dioxide. Common pathogenic species: N. gonorrhoeae and N. meningitidis.

    • Neisseria: N. gonorrhoeae is a major sexually transmitted disease (STD) cause. N. meningitidis causes serious, life-threatening meningitis, sometimes with rash.

    • Moraxella catarrhalis: Causes localized respiratory tract infections, including sinusitis and pneumonia, commonly affecting elderly patients and those with COPD (chronic obstructive pulmonary disease).

    • Gram-negative bacilli: Include species within the Enterobacteriaceae family. These are non-spore forming, facultative anaerobes, and primarily motile but Klebsiella and Shigella are notable exceptions. Most are glucose fermenters, and catalase positive (except Shigella dysenteriae).

    • Enterobacteriaceae: Many are motile at 37°C but species like Yersinia pestis are motile at 25°C but not 37°C. Species vary in whether they are rapid or slow lactose and/or sucrose fermenters. Many produce gas and H2S. Significant differences exist in their reactions to various biochemical tests (e.g., IMVIC, LIA, TSI, etc.). Critically, Shigella species are xylose non-fermenters.

    • HACEK group: Include Haemophilus spp., Aggregatibacter actinomycetemcomitans, Cardiobacterium hominis, Eikenella corrodens, and Kingella spp.. Known for fastidious nutritional requirements and need for increased CO2.

    Other Gram-Negative Bacteria

    • Vibrio, Aeromonas, Plesiomonas, Chromobacterium: These bacteria possess certain characteristics: curved comma shape, polar or peritrichous flagella, facultatively anaerobic, rapid darting/shooting star motility, and are oxidase and catalase positive. Except V. cholerae, species may be halophilic. V. cholerae causes cholera characterized by rice-water stool.

    • Campylobacter: Microaerophilic, curved/sea gull-winged, faintly staining, and associated with gastritis and diarrhea. Optimum temp for growth is 42-43°C and these are motile with a single polar flagellum.

    • Helicobacter: S-shaped, seagull wings, microaerophilic and associated with peptic ulcers. Rapid urease producer.

    Non-fermenting Gram-Negative Bacilli

    • Pseudomonas aeruginosa: An important opportunistic pathogen causing various community- and health-care-associated infections. Known for its characteristic odor, non-fermenter of glucose, and β-hemolysis. Growth at 42°C differentiates it from other Pseudomonas sp.

    • Burkholderia:

    • Burkholderia pseudomallei causes melioidosis. Characterized by bipolar staining and earthy oder.

    • Burkholderia cepacia is another important species of the genus, associated with cystic fibrosis. Nonfastidious.

    • Stenotrophomonas maltophilia: Often found in hospital settings, resistant to many drugs, and has a distinctive lavender-green colony. Oxidizes glucose and maltose strongly.

    • Acinetobacter: A variety of species exist within the genus, notable for their differences in oxidase and carbohydrate utilization. Some species grow at 42°C. Differentiable species include Acinetobacter baumannii, with a reputation for drug resistance and frequent infections. Nonmotile.

    Gram-Positive Bacilli and Other Bacteria

    • Listeria monocytogenes: Characterized by a ability to cross the placenta, causing perinatal infections. It is a gram-positive rod, and motile at 22°C.

    • Erysipelothrix rhusiopathiae: Causes veterinary infections and can be an occupational hazard for those who work with meat, poultry or fish. Gram-positive rod, nonmotile, and catalase negative, while producing H2S.

    • Lactobacillus and Gardnerella vaginalis: Not typically pathogenic, although Gardnerella vaginalis is associated with vaginal discharge and "clue cells."

    • Mycobacterium: Includes M. tuberculosis (tuberculosis) causing lung granulomas and Nontuberculous mycobacteria (NTM), that are found in the environment or can colonize humans.

    • Actinomyces, Nocardia, Tropheryma whipplei, etc.: are distinct bacteria types.

    • Chlamydia, Mycoplasma, Rickettsiae: These are obligate intracellular bacteria, with diverse pathogenic species and unique characteristics. C. psittaci infects birds and humans.

    • Borrelia, Leptospira, Treponema: These are spirochetes, with significant pathogenic roles in relapsing fevers, Weil disease (Leptospirosis), and syphilis. Treponemal infections typically involve skin and mucous membranes. Transmission is often linked to sexual or non-sexual contact.

    • Streptobacillus: Frequently associated with various fevers and also normal oral biota

    • Haemophilus: Fastidious, gram-negative coccobacilli, needing X and V factors and capnophilic conditions (5% to 10% CO2 at 35°C to 37°C for up to 3 days).

    • Brucella and Francisella tularensis: Important zoonotic pathogens, typically acquired through exposure to infected animals or their products.

    • Legionella: Associated with water sources, especially in hospital settings, and L. pneumophila is a frequent cause of pneumonia in humans.

    • Clostridia (anaerobic): This group includes C. perfringens, known for food poisoning; C. botulinum, associated with various forms of botulism through food or wound contamination; and C. tetani responsible for tetanus. Key characteristic is that they are gram-positive and anaerobes. These are noted for producing various toxins.

    • Corynebacterium diphtheriae: Causes diphtheria, characterized by inflammation and pseudomembrane formation in the throat.

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    Bacterial Classification - PDF

    Description

    This quiz covers the classification and characteristics of gram-negative cocci and bacilli, focusing on genera such as Neisseria and Moraxella. It also explores the pathogenic species associated with these bacteria and their clinical significance. Test your understanding of these important microorganisms.

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