1050 Unit 5 - bacteria and symbiosis
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Questions and Answers

What type of organism is Helicobacter pylori?

  • Gram-positive bacterium
  • Gram-negative, urease-producing bacterium (correct)
  • Fungus
  • Virus

    • How is an H pylori infection MOST commonly diagnosed?

  • X-ray imaging
  • Blood culture
  • PCR test for Mycoplasma pneumoniae
  • Urease detection in stomach biopsy tissue (correct)

    • Which test is considered the gold standard for diagnosing Rocky Mountain spotted fever (RMSF)?

  • Urine antigen test
  • Serologic testing for antibodies to Rickettsia rickettsii by IFA (correct)
  • Blood culture for Rickettsia
  • PCR for Mycoplasma pneumoniae

    • What distinguishes Mycoplasma pneumoniae from other bacteria?

    <p>It lacks a cell wall.</p> Signup and view all the answers

    What method is commonly used to detect Mycoplasma pneumoniae in patients?

    <p>Serologic assays for antibodies</p> Signup and view all the answers

    Which of the following diseases is classified as a non-suppurative manifestation of Group A streptococcal infection?

    <p>Necrotizing fasciitis</p> Signup and view all the answers

    What is the most common sequelae associated with Group A streptococcal infection that involves heart complications?

    <p>Acute rheumatic fever</p> Signup and view all the answers

    Which of the following symptoms is NOT associated with poststreptococcal glomerulonephritis?

    <p>Joint pain</p> Signup and view all the answers

    What ASO titer value is considered a positive test result?

    <p>Greater than 166 Todd units</p> Signup and view all the answers

    What characteristic is expected in the laboratory culture of a Group A streptococcal infection?

    <p>Small translucent colonies surrounded by clear zones of beta hemolysis</p> Signup and view all the answers

    What is the main method used for serologic detection of Group A streptococcal sequelae?

    <p>Antistreptolysin O (ASO) titer</p> Signup and view all the answers

    Which method is currently the method of choice for testing H pylori antibodies?

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

    Which condition can potentially result from a skin infection with Group A streptococcus?

    <p>Poststreptococcal glomerulonephritis</p> Signup and view all the answers

    Which characteristic is NOT true regarding Mycoplasma pneumoniae?

    <p>Can be cultured easily in clinical laboratories</p> Signup and view all the answers

    What is the primary route of transmission for Helicobacter pylori?

    <p>Fecal-oral route</p> Signup and view all the answers

    Which factor is responsible for the symptoms associated with acute rheumatic fever?

    <p>Immune responses to streptococcal antigens</p> Signup and view all the answers

    What is the typical timeframe for the development of acute rheumatic fever after a streptococcal infection?

    <p>1 to 3 weeks</p> Signup and view all the answers

    What is a common complication if Helicobacter pylori infection remains untreated? Select all that apply.

    <p>Mucosa-associated lymphoid tumors</p> Signup and view all the answers

    What percentage of acute rheumatic fever patients will display an elevation in ASO titer?

    <p>85%</p> Signup and view all the answers

    What characteristic feature is displayed by Mycoplasma pneumoniae colonies in culture?

    <p>Fried egg appearance</p> Signup and view all the answers

    Which test detects antibodies to five streptococcal products including ASO?

    <p>Streptozyme test</p> Signup and view all the answers

    What indicates an active Helicobacter pylori infection in serum tests?

    <p>IgG in serum</p> Signup and view all the answers

    Which condition is associated with Mycoplasma pneumoniae in a minority of cases?

    <p>Stevens-Johnson</p> Signup and view all the answers

    What type of antibodies are indicative of a recent infection with Mycoplasma pneumoniae?

    <p>IgM antibodies</p> Signup and view all the answers

    Which infectious agent is transmitted by ticks and can cause Rocky Mountain spotted fever?

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

    What are cold agglutinins associated with, and what percentage of infected patients typically have them?

    <p>Mycoplasma infection; 50%</p> Signup and view all the answers

    Which of the following is a typical symptom of Rocky Mountain spotted fever?

    <p>Skin rash</p> Signup and view all the answers

    What laboratory method is commonly used to diagnose acute streptococcal infections?

    <p>Sheep blood agar culture</p> Signup and view all the answers

    What characterizes the virulence factors of bacteria discussed in the content?

    <p>Virulence factors include structural components and toxins.</p> Signup and view all the answers

    What is the role of serologic methods in the diagnosis of streptococcal sequelae?

    <p>To detect antibodies to streptococcal antigens.</p> Signup and view all the answers

    What is the primary target for molecular detection methods in bacterial infections?

    <p>Bacterial nucleic acids</p> Signup and view all the answers

    What type of defense mechanisms are included in the innate defenses against bacteria?

    <p>Antimicrobial defense peptides</p> Signup and view all the answers

    Which of the following statements about endotoxins is true?

    <p>Endotoxins can lead to cytokine production and death.</p> Signup and view all the answers

    What term describes the relationship where both the host and microbes benefit?

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

    Which bacterial structure is specifically involved in adherence to host cells and resistance to phagocytosis?

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

    Which of the following is a component of innate immune defenses against bacteria?

    <p>Intact skin and mucosal surfaces</p> Signup and view all the answers

    What is the primary purpose of culture methods in laboratory detection of bacterial infections?

    <p>To grow the causative agent for diagnosis</p> Signup and view all the answers

    What signifies a current infection when comparing acute and convalescent sample titers?

    <p>A fourfold rise in antibody titer</p> Signup and view all the answers

    How do exotoxins differ from endotoxins?

    <p>Exotoxins are toxic proteins released from living bacteria, endotoxins are part of the bacteria's structure.</p> Signup and view all the answers

    Which mechanism is used by bacteria to evade immune responses?

    <p>Inhibiting complement c3b binding</p> Signup and view all the answers

    What type of laboratory detection method provides DNA results within a few hours?

    <p>PCR molecular detection</p> Signup and view all the answers

    What does the presence of IgM antibodies indicate in the context of bacterial infections?

    <p>Current infection</p> Signup and view all the answers

    Which bacterial infection detection method involves the analysis of proteins produced by specific bacteria?

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

    What characterizes group A streptococci in terms of their gram stain reaction?

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

    What is the main disadvantage of serological testing in bacterial infection diagnosis?

    <p>There is a delay in patient antibody production.</p> Signup and view all the answers

    What helps pathogens to block phagocytosis during infections?

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

    What is the primary clinical manifestation of primary stage syphilis?

    <p>Development of chancre</p> Signup and view all the answers

    Which symptom is NOT typically associated with secondary stage syphilis?

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

    What characterizes the latent stage of syphilis?

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

    Which complication may arise in infants born with congenital syphilis?

    <p>Saber shins</p> Signup and view all the answers

    What is used in dark-field microscopy to help diagnose syphilis?

    <p>Treponemes in active lesions</p> Signup and view all the answers

    What do nontreponemal tests primarily detect in the diagnosis of syphilis?

    <p>Antibodies against cardiolipin</p> Signup and view all the answers

    Which stage of syphilis is characterized by gummatous lesions?

    <p>Tertiary stage</p> Signup and view all the answers

    How can congenital syphilis affect newborns?

    <p>They may develop symptoms like skin rash later</p> Signup and view all the answers

    What is a characteristic feature of spirochete bacteria?

    <p>They contain axial filaments that assist in motility.</p> Signup and view all the answers

    What clinical manifestation is common to many diseases caused by spirochetes?

    <p>Development of a latent stage.</p> Signup and view all the answers

    Which of the following is NOT a known complication of untreated spirochete infections?

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

    Which classification describes the oxygen requirements of spirochete bacteria?

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

    What is a common route of transmission for spirochete diseases like Lyme disease?

    <p>Vector-borne via ticks</p> Signup and view all the answers

    What type of infections are spirochete bacteria primarily associated with?

    <p>Chronic systemic infections</p> Signup and view all the answers

    In what form do spirochetes typically exhibit their motility?

    <p>Corkscrew flexion</p> Signup and view all the answers

    What is a defining feature of spirochete diseases in terms of progression?

    <p>There is a pattern of disseminating to multiple organs.</p> Signup and view all the answers

    What is the primary way syphilis is spread?

    <p>By direct contact with an open lesion</p> Signup and view all the answers

    Which bacterium is identified as the causative agent of syphilis?

    <p>Treponema pallidum</p> Signup and view all the answers

    Which of the following organisms is NOT a subspecies of Treponema pallidum?

    <p>Treponema carateum</p> Signup and view all the answers

    Which statement regarding the transmission of syphilis to a fetus is true?

    <p>It can be transmitted during pregnancy</p> Signup and view all the answers

    What factor significantly affects the survivability of Treponema pallidum outside the body?

    <p>Heat, cold, and drying</p> Signup and view all the answers

    What is the primary purpose of nontreponemal tests like the VDRL and RPR?

    <p>To detect antibodies to cardiolipin</p> Signup and view all the answers

    Why are treponemal tests considered more specific than nontreponemal tests?

    <p>They target antibodies to T.pallidum</p> Signup and view all the answers

    What happens to nontreponemal antibody titers over time in a patient with syphilis?

    <p>They decline in later stages and during effective treatment</p> Signup and view all the answers

    What is a characteristic feature of Lyme disease?

    <p>An expanding red rash at the tick bite site</p> Signup and view all the answers

    What is the gold standard test for confirmation of leptospirosis?

    <p>Microscopic agglutination test (MAT)</p> Signup and view all the answers

    How long does it typically take for antibodies to B.burgdorferi to be detected after a tick bite?

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

    Which testing algorithm screens patient samples with a nontreponemal test first?

    <p>Traditional testing algorithm</p> Signup and view all the answers

    Which of the following symptoms is NOT associated with untreated Lyme disease?

    <p>Golden-yellow discharge at the bite site</p> Signup and view all the answers

    What indicates a positive result in the TP-PA test?

    <p>Smooth mat covering the surface</p> Signup and view all the answers

    Which testing algorithm begins with nontreponemal testing?

    <p>Traditional Testing Algorithm</p> Signup and view all the answers

    What is a common test performed on cerebrospinal fluid to diagnose neurosyphilis?

    <p>CSF VDRL</p> Signup and view all the answers

    What does an absence of fluorescence indicate in a syphilis test?

    <p>A negative test</p> Signup and view all the answers

    In which condition would IgM-specific treponemal assays be performed on both the mother and infant?

    <p>Congenital syphilis</p> Signup and view all the answers

    Which assay is performed to confirm positive results from an automated immunoassay in the Reverse Sequence Algorithm for Syphilis?

    <p>RPR test</p> Signup and view all the answers

    What is the purpose of performing polymerase chain reaction (PCR) in syphilis testing?

    <p>As a potential method for detecting T.pallidum DNA</p> Signup and view all the answers

    What denotes a reactive test result in serological testing for syphilis?

    <p>A result of 2+ or above</p> Signup and view all the answers

    Which proteins are significant in differentiating serotypes of streptococci?

    <p>M and T proteins</p> Signup and view all the answers

    Streptococci can be divided into groups based on the Lancefield classification system.

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

    What is the significance of hyaluronic acid capsules in certain streptococci strains?

    <p>They block phagocytosis</p> Signup and view all the answers

    Match the following virulence factors of streptococci with their functions:

    <p>M protein = Adherence and resistance to phagocytosis DNase B = Degradation of DNA in host tissues Streptokinase = Facilitates spread by dissolving blood clots Hyaluronidase = Breakdown of hyaluronic acid in connective tissue</p> Signup and view all the answers

    Which test is used to detect the presence of Helicobacter pylori antigens in stool samples?

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

    Mycoplasma pneumoniae has a cell wall and is a major cause of respiratory infections.

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

    What type of bacteria are Rickettsia, and how are they primarily transmitted?

    <p>Obligate intracellular gram-negative bacteria, transmitted by ticks</p> Signup and view all the answers

    The disease caused by Rickettsia that is characterized by a rash and fever is called __________.

    <p>Rocky Mountain spotted fever</p> Signup and view all the answers

    Match the following testing methods to their bacteria:

    <p>Urea breath test = Helicobacter pylori Cold agglutinins = Mycoplasma pneumoniae Serologic testing = Rickettsia PCR = Mycoplasma pneumoniae</p> Signup and view all the answers

    Which of the following is a suppurative manifestation of Group A streptococcal infection?

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

    Acute rheumatic fever can develop 1 to 3 weeks after a strep throat infection.

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

    What type of culture is used for diagnosing acute Group A streptococcal infections?

    <p>Sheep blood agar</p> Signup and view all the answers

    Poststreptococcal glomerulonephritis may follow a strep infection of the skin or ______.

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

    What is the primary method for detecting streptococcal antibodies in serologic tests?

    <p>ASO titer</p> Signup and view all the answers

    Match the following clinical manifestations with their corresponding types:

    <p>Pharyngitis = Suppurative Scarlet fever = Non-suppurative Pyoderma = Suppurative Toxic shock syndrome = Non-suppurative</p> Signup and view all the answers

    What type of immune response is primarily responsible for the symptoms of acute rheumatic fever?

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

    Beta hemolysis is characterized by the presence of a clear zone surrounding small translucent colonies on sheep blood agar.

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

    What ASO titer value indicates a positive test?

    <blockquote> <p>200 IU</p> </blockquote> Signup and view all the answers

    Antistreptolysin O (ASO) titers typically increase in patients with streptococcal skin infections.

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

    What is the method of choice to detect Helicobacter pylori antigens in clinical settings?

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

    The primary transmission route for Helicobacter pylori is through the ______ route.

    <p>fecal-oral</p> Signup and view all the answers

    Match the following bacteria with their associated features:

    <p>Streptococcus = Causes rheumatic fever Helicobacter pylori = Major cause of gastric ulcers Mycoplasma pneumoniae = Causes 'walking pneumonia' Staphylococcus = Can cause skin infections</p> Signup and view all the answers

    All patients with acute rheumatic fever show elevated ASO titers.

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

    Name one complication that can arise from untreated Helicobacter pylori infection.

    <p>Gastric carcinoma</p> Signup and view all the answers

    Which test detects antibodies to five streptococcal products?

    <p>Streptozyme test</p> Signup and view all the answers

    Which of the following correctly describes the term 'pathogenicity'?

    <p>The extent of pathology caused by an organism when it infects a host</p> Signup and view all the answers

    Virulence refers to the level of harm that an organism can inflict on the host.

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

    What is the primary component of the lipopolysaccharide (LPS) in gram-negative bacteria that acts as an endotoxin?

    <p>Lipid A</p> Signup and view all the answers

    Match the following bacterial structures with their respective functions:

    <p>Pili = Adherence to host cells, resistance to phagocytosis Flagella = Motility Capsule = Blocking phagocytosis and antibody attachment Exotoxins = Toxic proteins released from living bacteria</p> Signup and view all the answers

    Which method allows for the rapid detection of bacterial antigens?

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

    Adaptive immune responses fully develop immediately after exposure to an infection.

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

    Name the first line of innate defense against bacterial infections.

    <p>Intact skin</p> Signup and view all the answers

    Bacteria that live together with the host without helping or harming are referred to as ______.

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

    What is a significant disadvantage of serological testing for bacterial infections?

    <p>Delay between infection and antibody production</p> Signup and view all the answers

    Exotoxins are released from dead bacteria.

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

    What is the main method used to culture the causative agent of a bacterial infection?

    <p>Grow on broth or solid media</p> Signup and view all the answers

    Match the following immune defense mechanisms to their descriptions:

    <p>Antibody production = Adaptive defenses Intact skin = Innate defenses Cytotoxic T lymphocytes = Cell-mediated immunity Complement proteins = Innate defenses</p> Signup and view all the answers

    Which stage of syphilis is characterized by generalized lymphadenopathy and rash?

    <p>Secondary stage</p> Signup and view all the answers

    Tertiary syphilis can lead to conditions like gummatous lesions and cardiovascular problems.

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

    What is the main treatment for early-stage syphilis?

    <p>Antibiotics like penicillin</p> Signup and view all the answers

    Congenital syphilis may cause death in ___% of cases.

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

    Match the stage of syphilis with its characteristic:

    <p>Primary = Development of chancre Secondary = Generalized lymphadenopathy Latent = Asymptomatic Tertiary = Gummatous lesions</p> Signup and view all the answers

    Which test detects the anti-cardiolipin antibody called reagin?

    <p>Venereal Disease Research Laboratory (VDRL) test</p> Signup and view all the answers

    Infants born with congenital syphilis are always symptomatic at birth.

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

    Which disease is caused by spirochete bacteria?

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

    Lyme disease and leptospirosis have the same causal organism.

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

    What result indicates a positive test in the TP-PA Test?

    <p>Agglutination that forms a smooth mat</p> Signup and view all the answers

    The __________ stage of syphilis is characterized by the absence of symptoms.

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

    A negative test for syphilis requires a fluorescence indication.

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

    What are the two main test categories in the traditional algorithm used to diagnose syphilis?

    <p>Nontreponemal testing and treponemal testing</p> Signup and view all the answers

    Match the spirochete disease with its corresponding characteristic:

    <p>Syphilis = Tabes dorsalis Lyme disease = Erythema migrans Leptospirosis = A zoonotic infection Leptospirosis = Can lead to Weil’s disease if left untreated</p> Signup and view all the answers

    What characteristic helps spirochetes move?

    <p>Axial filaments</p> Signup and view all the answers

    Perform ____ tests on the mother and infant to confirm congenital syphilis.

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

    All spirochete diseases present only localized symptoms.

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

    Match the following terms related to syphilis testing with their descriptions:

    <p>RPR = A rapid test for detecting syphilis TP-PA = Test that detects antibodies to Treponema pallidum IgM-specific treponemal assays = Used to confirm congenital syphilis CSF VDRL = Test performed on cerebrospinal fluid for neurosyphilis</p> Signup and view all the answers

    Which of the following is a typical pattern of testing for congenital syphilis?

    <p>Nontreponemal tests on the mother and infant</p> Signup and view all the answers

    What type of bacteria are spirochetes classified as?

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

    Lyme disease is transmitted by Ixodes ticks.

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

    What is the main reservoir for Lyme disease?

    <p>White-footed mouse</p> Signup and view all the answers

    What is the main function of nontreponemal tests such as VDRL and RPR?

    <p>To detect antibody to cardiolipin</p> Signup and view all the answers

    Treponemal antibody titers will decline after successful treatment of syphilis.

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

    What is the characteristic feature of Lyme disease?

    <p>An expanding red rash at the site of the tick bite</p> Signup and view all the answers

    The gold standard for confirming a diagnosis of leptospirosis is the _____ test.

    <p>microscopic agglutination</p> Signup and view all the answers

    Match the Treponema strain with its relevant disease:

    <p>T. pallidum pallidum = Syphilis (worldwide) T. pallidum endimecum = Nonvenereal endemic syphilis (desert) T. pallidum pertenue = Yaws (tropics) T. carateum = Pinta (Central &amp; South America)</p> Signup and view all the answers

    In the traditional testing algorithm for syphilis, which type of test is used first?

    <p>Nontreponemal test</p> Signup and view all the answers

    Antibodies to Borrelia burgdorferi can be detected within days after a tick bite.

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

    What type of organism causes leptospirosis?

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

    What test is performed to look for flocculation in patient serum?

    <p>Rapid Plasma Reagin (RPR) Test</p> Signup and view all the answers

    In the RPR test, patient serum is mixed with __________ particles coated with cardiolipin antigen.

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

    Automated immunoassays are not used for detecting antibodies to T.pallidum.

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

    Study Notes

    Host-Microbe Relationships

    • Host and microbes can have symbiotic, commensalistic, mutualistic, or parasitic relationships
    • Symbiotic relationships involve long-term cohabitation
    • Commensalistic relationships have no benefit or harm to either organism
    • Mutualistic relationships provide benefits for both the host and the microbe
    • Parasitic relationships harm the host

    Infectivity, Pathogenicity, and Virulence

    • Infectivity measures an organism's ability to establish an infection
    • Pathogenicity describes an organism's ability to cause disease
    • Virulence assesses the extent of pathology caused by an organism during infection

    Structural Components of Bacteria

    • Endotoxin is the lipid A portion of lipopolysaccharide (LPS) found in gram-negative cell walls
    • Endotoxin is a powerful stimulator of cytokine release
    • Pili are hair-like structures that aid in adherence to host cells and provide resistance to phagocytosis
    • Flagella are whip-like structures that facilitate adherence to host cells and motility
    • Capsule is an outer layer that blocks phagocytosis, antibody attachment, and complement activation

    Bacterial Virulence Factors

    • Exotoxins are potent toxic proteins released from living bacteria
    • Exotoxins can be classified as neurotoxins, cytotoxins, or enterotoxins

    Immune Defenses Against Bacteria

    • Innate defenses include barriers like skin and mucosal surfaces, antimicrobial peptides, complement proteins, cytokines, and acute-phase reactants
    • Adaptive defenses involve antibody production, complement activation (opsonization, neutralization), and cell-mediated immunity

    Bacterial Evasion Mechanisms

    • Bacteria can evade the immune system by inhibiting chemotaxis, blocking phagocyte adherence, inhibiting digestion, preventing complement binding, and cleaving IgA

    Laboratory Detection of Bacterial Infections

    • Culture methods involve growing bacteria on broth or solid media
    • Microscopic examination techniques include Gram staining and special staining
    • Detection of bacterial antigens can be performed using rapid tests like ELISA, LFA, and LA
    • Molecular detection of bacterial DNA or RNA utilizes PCR for faster results
    • Proteomics analyzes proteins produced by bacteria

    Laboratory Detection of Bacterial Infections (Continued)

    • Serologic methods detect antibodies to bacterial antigens
    • Serology can be used to:
      • Detect and confirm infections when other methods are unavailable
      • Diagnose infections with nonspecific clinical symptoms
      • Determine current infection through IgM, high IgG titer, or fourfold rise in antibody titer
      • Identify past exposure to an organism (IgM negative, IgG positive)
      • Assess reactivation or re-exposure
    • Serology disadvantages:
      • Delay between infection and antibody production
      • Low antibody production in immunosuppressed patients

    Streptococci (GAS)

    • Streptococci are gram-positive, catalase-negative cocci often seen in pairs or chains

    Clinical Manifestations of Acute Group A Streptococcal Infection

    • Suppurative infections include pharyngitis (strep throat) and pyoderma (impetigo)
    • Non-suppurative infections include scarlet fever, toxic shock syndrome, and necrotizing fasciitis
    • Treatment for streptococcal infections involves antibiotics

    Group A Streptococcal Sequelae

    • Acute rheumatic fever:
      • Develops 1 to 3 weeks after pharyngitis or tonsillitis
      • Symptoms include fever, joint pain, and heart inflammation
      • Caused by cross-reactivity between streptococcal antigens and human heart tissue
    • Poststreptococcal glomerulonephritis:
      • Can follow streptococcal infection of the skin or pharynx
      • Damages glomeruli causing hematuria, proteinuria, edema, and renal impairment

    Laboratory Diagnosis of Acute Group A Streptococcal Infections (Suppurative)

    • Culture on sheep blood agar: produces small translucent colonies surrounded by beta-hemolysis
    • Rapid assays for group A streptococcal antigens: Strep Screens, LFA

    Serologic Detection of Group A Streptococcal Sequelae

    • Antistreptolysin O (ASO):
      • Classic hemolytic method measures antibody neutralization of streptolysin O hemolytic activity
      • Titer > 166 Todd units (or >200 IU) indicates a positive test
      • Nephelometric methods measure light scatter produced by immune complexes
      • Elevated titers in 85% of acute rheumatic fever patients
      • Does not increase in skin infection patients
    • Anti-DNase B:
      • Produced in both rheumatic fever and impetigo patients
      • Tested by EIA and nephelometric methods
    • Streptozyme test:
      • Detects antibodies to five streptococcal products: ASO, AHase, ASKase, Anti-NAD, and Anti-DNase B

    Helicobacter pylori

    • Gram-negative, microaerophilic, spiral bacterium
    • Transmitted likely by fecal-oral route
    • Major cause of gastric and duodenal ulcers
    • Survives in the acidic stomach environment due to urease production
    • Treated with antibiotics and anti-ulcer medications
    • Untreated infections can lead to gastric carcinoma or MALT tumors

    Detection of Helicobacter pylori Infection

    • Detection of urease in stomach biopsy (CLOtest)
    • Urea breath test
    • H. pylori antigens
    • H. pylori antibodies (ELISA is the method of choice, IgG indicates active infection, titers decrease after successful treatment)

    Mycoplasma pneumoniae

    • Tiny bacteria lacking a cell wall
    • Leading cause of respiratory infections (fever, headache, malaise, cough, walking pneumonia, Raynaud syndrome)
    • Can cause Stevens-Johnson syndrome in some cases
    • Spread by respiratory droplets

    Laboratory Diagnosis of M. pneumoniae Infection

    • Culture: produces mulberry colonies with a "fried egg" appearance
    • Antibodies to M. pneumoniae: IgM antibodies indicate recent infection, IgG antibodies suggest possible reinfection
    • Cold agglutinins: present in ~50% of patients, but not specific, cause RBC agglutination at 4°C (reversible at 37°C)
    • Molecular methods: Film array respiratory panel

    Rickettsial Infections

    • Obligate intracellular gram-negative bacteria transmitted by arthropods
    • Spotted fever group (SPF): e.g., Rocky Mountain spotted fever
    • Typhus group (TG): e.g., epidemic typhus

    Rocky Mountain Spotted Fever (RMSF)

    • Caused by Rickettsia rickettsii
    • Transmitted by three species of ticks
    • Symptoms include headache, nausea, vomiting, diarrhea, skin rash, and potentially death
    • Diagnosis: clinical presentation, serology by IFA

    Summary

    • Host-microbe relationships fall into four categories: symbiotic, commensalistic, mutualistic, and parasitic
    • Bacterial virulence factors contribute to disease-causing ability, including endotoxin, pili, flagella, capsule, and exotoxins
    • Immune defenses against bacteria include innate barriers like skin and mucous membranes, antimicrobial peptides, and adaptive responses like antibody production and cell-mediated immunity
    • Laboratory detection of bacterial infections can involve culture, staining, rapid antigen detection, molecular methods, and serology

    Group A Streptococci

    • Gram-positive bacteria causing upper respiratory tract and skin infections
    • Sequelae include acute rheumatic fever and poststreptococcal glomerulonephritis
    • Diagnostic techniques include sheep blood agar culture, rapid antigen detection, and serologic tests (ASO, anti-DNase B, Streptozyme)

    Helicobacter pylori

    • Gram-negative, urease-producing bacterium causing gastric ulcers
    • Untreated infections can lead to gastric carcinoma or MALT tumors
    • Detection methods include urease detection, urea breath test, H. pylori antigen tests, and serologic tests

    Mycoplasma pneumoniae

    • Tiny, cell wall-lacking bacteria causing respiratory infections
    • Diagnosis uses serologic testing for antibodies and PCR for DNA detection
    • Cold agglutinins can be present, but are not specific for infection

    Rickettsial Infections

    • Transmitted by arthropods
    • Spotted fever group (SPF) and typhus group (TG)
    • Rocky Mountain spotted fever (RMSF) caused by R. rickettsii
    • RMSF diagnosis involves clinical presentation and serologic testing by IFA

    Syphilis

    • A sexually transmitted disease caused by the spirochete bacterium Treponema pallidum
    • Rapidly destroyed by heat, cold, and drying
    • Direct contact with an open lesion is necessary for transmission
    • Transmission to the fetus can occur during pregnancy
    • Bloodborne transmission is rare
    • Most commonly acquired spirochete disease in the United States
    • Typically spread through sexual transmission

    Stages of Syphilis

    • Primary stage:
      • Development of a chancre
    • Secondary stage:
      • Generalized lymphadenopathy, malaise, fever, pharyngitis, rash
    • Latent stage:
      • Asymptomatic
    • Tertiary stage:
      • Gummatous, cardiovascular, neurosyphilis, tabes dorsalis (shuffling gate)

    Congenital Syphilis

    • Transmission of treponemes to the fetus occurs when a pregnant woman has early-stage or latent syphilis
    • Causes death in approximately 10% of cases
    • Live-born infants may be asymptomatic at birth but develop symptoms later:
      • Runny nose, skin rash, generalized lymphadenopathy, hepatosplenomegaly, jaundice, anemia, bone abnormalities such as saddle nose or saber shins, neurosyphilis

    Laboratory Diagnosis of Syphilis

    • Direct Detection

      • Demonstration of treponemes in active lesions
      • Dark-field microscopy
      • Fluorescent antibody staining

    • Serological Tests

      • Nontreponemal: Detect antibody against cardiolipin
        • Venereal Disease Research Laboratory (VDRL) test
      • Treponemal: More specific tests that detect antibodies to T. pallidum
        • Fluorescent Treponemal Antibody Absorption (FTA-ABS) test
        • T. pallidum particle agglutination (TP-PA) test
        • Automated ELISA for T. pallidum antibodies

    Lyme Disease

    • Caused by the spirochete bacterium Borrelia burgdorferi
    • Transmitted by Ixodes ticks
    • Main reservoir: white-footed mouse
    • Most common vector-borne disease in the United States

    Leptospirosis

    • A zoonosis caused by exposure to water contaminated with animal urine containing leptospires
    • Can progress to a severe illness that may involve renal or hepatic failure

    Laboratory Diagnosis of Leptospirosis

    • The gold standard for confirmation is the microscopic agglutination test (MAT)

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    Related Documents

    Bacterial Infections Lecture Notes PDF
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    Description

    This quiz explores the various types of relationships between hosts and microbes, including symbiotic, commensalistic, mutualistic, and parasitic interactions. Learn about the concepts of infectivity, pathogenicity, and virulence, as well as the structural components of bacteria that play crucial roles in these relationships.

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