Microbiology Antibiotic Testing and Serology
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Questions and Answers

What breakpoint indicates resistance for E.coli against Ampicillin?

  • 18 mm
  • 16 mm
  • 14 mm (correct)
  • 22 mm

    • Which test can be used to detect unknown antibodies?

  • By known antigen detection (correct)
  • By known antibody detection
  • Epidemiological research
  • Complete biochemical identification

    • What is considered a sensitive breakpoint for E.coli using Imipenem?

  • 14 mm
  • 16 mm
  • 18 mm
  • 22 mm (correct)

    • What is the function of the 'K antigen' in cellular components?

    <p>Capsule component</p> Signup and view all the answers

    Which antibiotic shows a breakpoint of 18 mm for resistance in P.aeruginosa?

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

    For E.coli, what is the breakpoint indicating sensitivity of Cefixime?

    <p>17 mm</p> Signup and view all the answers

    Which serological test function involves determining the spreading of serotypes?

    <p>Epidemiological research</p> Signup and view all the answers

    The 'O antigen' is a component of which cellular structure?

    <p>Cell wall</p> Signup and view all the answers

    What is the effect of heat on complement in serum?

    <p>It is heat labile and can be inactivated</p> Signup and view all the answers

    Which cytokines stimulate the production of C reactive protein?

    <p>IL-1 and IL-6</p> Signup and view all the answers

    What is the normal concentration of C reactive protein in serum?

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

    What type of test is used for the detection of antibodies?

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

    Which of the following is NOT a method of detecting agglutination?

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

    What characteristic is true of quantitative serological tests?

    <p>They measure the concentration of antibodies specifically</p> Signup and view all the answers

    When does C reactive protein reach its maximum concentration after production?

    <p>48 hours</p> Signup and view all the answers

    Which category of serological tests includes both visible and invisible methods?

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

    What is the main characteristic of slide agglutination?

    <p>Ab is known and Ag is unknown.</p> Signup and view all the answers

    In tube agglutination, what does the titer indicate?

    <p>The lowest dilution at which agglutination is visible.</p> Signup and view all the answers

    What role does Protein-A play in co-agglutination with Staphylococcus aureus?

    <p>It binds IgG at Fc receptors.</p> Signup and view all the answers

    Which test is an example of tube agglutination used for typhoid fever diagnosis?

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

    What type of agglutination uses latex granules as carriers?

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

    What characterizes precipitation reactions?

    <p>Ag must be soluble in the medium.</p> Signup and view all the answers

    In which medium does ring precipitation occur?

    <p>Fluid medium.</p> Signup and view all the answers

    Which agglutination test specifically involves Rickettsia prowazekii?

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

    What experiment utilizes a known artificial antigen to detect unknown antibodies in patient serum?

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

    In the Quellung reaction, what is the observable change if the test is positive?

    <p>Opacification and growth of the capsule</p> Signup and view all the answers

    What type of antigen is used in the Elek test?

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

    Which component of the ELISA test is labeled with an enzyme?

    <p>Antihuman globulin</p> Signup and view all the answers

    What is the primary purpose of ring precipitation in immunological testing?

    <p>To determine the presence of a soluble antigen</p> Signup and view all the answers

    Which test specifically indicates the presence of toxin-producing strains of bacteria?

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

    In the context of the Quellung reaction, what does a positive result indicate about the unknown bacteria?

    <p>The bacteria has a capsule that reacts with antibodies</p> Signup and view all the answers

    Which of the following statements correctly describes the role of antibodies in the ELISA technique?

    <p>They help in detecting unknown antigens in patient serum</p> Signup and view all the answers

    What is the role of labeled antibodies in the immunofluorescent method?

    <p>They emit fluorescence when exposed to UV light.</p> Signup and view all the answers

    In the indirect immunofluorescent method, which component is unlabeled?

    <p>Primary antibody</p> Signup and view all the answers

    Which type of antigen is specifically mentioned in the context of direct immunofluorescence?

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

    What is one characteristic of the direct immunofluorescent method?

    <p>It uses labeled antibodies that recognize specific antigens.</p> Signup and view all the answers

    What is the primary use of the immunofluorescent method?

    <p>To visualize pathogens in tissues.</p> Signup and view all the answers

    Which of the following best describes the 'indirect' method of immunofluorescence?

    <p>Requires multiple steps with unlabeled antibodies initially.</p> Signup and view all the answers

    What characteristic distinguishes direct immunofluorescence from indirect immunofluorescence?

    <p>Direct immunofluorescence employs labeled antibodies to detect unknown antigens.</p> Signup and view all the answers

    In the immunofluorescent method, what kind of dye is mentioned for labeling antibodies?

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

    Study Notes

    Antibiotic Sensitivity Tests

    • EUCAST is the European Committee on Antimicrobial Susceptibility Testing
    • Standardized test for sensitivity to antibiotics, reported as:
      • S: Susceptible
      • R:Resistant
    • S. aureus: Staphylococcus aureus
    • E.coli: Escherichia coli
    • P. aeruginosa: Pseudomonas aeruginosa

    Serological Reactions

    • Serological tests are used to identify antibodies (Ab), antigens (Ag) or previous infections
    • Antigens are proteins or molecules that trigger an immune response, including:
      • O antigen: cell wall
      • H antigen: flagella
      • K antigen: capsule
      • F antigen: fimbria
    • Complement aids in the destruction of foreign invaders, and involves:
      • Lysis: The breakdown of cells
      • Opsonization: The coating of microbes for better phagocytosis
    • C-reactive protein (CRP) is a type of protein that increases during infection:
      • Normal levels: 10 mg/l
      • Viral infection: 30-40 mg/l
      • Bacterial infection: 200-250 mg/l
      • Fungal infection: 250-300 mg/l
    • Serological Tests can be used to detect:
      • Ag: Directly or from a culture
      • Ab: To demonstrate the presence of a disease or the effect of vaccines

    Classification of Serological Tests

    • Qualitative tests distinguish between the presence or absence of substances
    • Quantitative tests give a numerical value of the concentration of a substance in a sample.
    • Visible Tests include:
      • Agglutination: The clumping of particles
      • Precipitation: The formation of a solid in a solution
    • Invisible Tests require further detection methods, including:
      • Immunofluorescence (IF): Using fluorescent dyes
      • Complement Fixation Test (CFT): Identifying the presence of antibodies by their ability to fix complement
      • Radioimmunoassay (RIA): Using radioactive isotopes
      • Enzyme-Linked Immunosorbent Assay (ELISA): Using enzymes

    Agglutination

    • Slide agglutination is a qualitative test using:
      • Unknown Ag
      • Known Ab (specific sera)
    • Tube agglutination is a quantitative test, using:
      • Known Ag
      • Unknown Ab (diluted from patient serum)
      • Examples:
        • Gruber-Widal test for typhoid fever
        • Wright reaction for brucellosis
        • Weil-Felix reaction for Rickettsia prowazekii
    • Titer is the highest dilution fold, where agglutination is still visible

    Indirect Agglutination

    • Latex agglutination uses Ab bound to a carrier:
      • Carrier:
        • Red blood cells (hemagglutination)
        • Latex granules (latex agglutination)
        • Staphylococcus aureus (co-agglutination)
      • Protein A produced by S. aureus can bind to the Fc receptor of IgG

    Precipitation

    • Precipitation involves soluble Ag forming a solid with Ab in a solution
      • Ring precipitation is the formation of a ring at the junction of Ag and Ab
        • It is a quantitative test
      • Elek test uses filter paper with Ab against a toxin
        • Detects toxin production by a strain
        • If the strain is a toxin producer, a precipitation arch will be visible

    Quellung Reaction

    • Quellung reaction is used to identify bacteria with capsules
      • Unknown capsule-bearing bacteria (Ag)
      • Ab against the capsule
      • If positive, the capsule appears larger and more opaque

    ELISA

    • ELISA is a quantitative test that utilizes:
      • Known artificial Ag
      • Unknown Ab from patient sera
      • Ab*: Anti-human globulin labeled with an enzyme
    • Procedure:
      • Artifical Ag is adhered to a surface
      • Patient sera (containing Ab) is added
      • Ab (labeled)* is added and will bind to patient Ab
      • Substrate (enzyme specific) is added and will bind to the enzyme of Ab*

    Immunofluorescent Method (IF)

    • Direct IF:
      • Ag: Unknown (unlabeled)
      • Ab: Known, labeled with fluorescent dye
    • Indirect IF:
      • Ag: Known
      • Ab: Unknown
      • Ab*: Labeled antiglobulin
    • Procedure:
      • Ag and Ab interact
      • Viewed under UV light, fluorescence indicates positivity

    Vaccines

    • Vaccines are used to stimulate the immune system to produce antibodies against a pathogen
      • Live-attenuated: Contain weakened versions of the pathogen
      • Inactivated: Contain killed versions of the pathogen.
      • Subunit: Contain only specific parts of the pathogen.

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    Serology Handout PDF

    Description

    This quiz covers essential topics in microbiology, including the EUCAST standard for antibiotic sensitivity testing and various serological reactions. You'll explore the significance of antigens and the role of complement in immune responses. Test your knowledge on S. aureus, E. coli, and P. aeruginosa along with serological markers like C-reactive protein.

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