Mueller-Hinton Agar Test Medium in Clinical Bacteriology
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Questions and Answers

What does the agar thickness affect in the agar dilution method?

  • Microbial growth
  • Antibiotic concentration
  • Incubation time
  • Inhibition zone size (correct)
  • What does a spot on the agar surface after incubation indicate?

  • High antibiotic concentration
  • Low bacterial count
  • No inhibition
  • Growth of bacteria (correct)
  • What does a large inhibition zone in the disk diffusion method suggest?

  • Inadequate antibiotic concentration
  • Resistant bacteria
  • Susceptible bacteria (correct)
  • No bacteria present
  • What is one advantage of the agar dilution method over broth mediums?

    <p>Determining MICs for N.gonorrhoeae</p> Signup and view all the answers

    Why is the disk diffusion method also known as the Kirby Bauer method?

    <p>Uses disks with a known concentration of antimicrobial agent</p> Signup and view all the answers

    What problem is associated with agar that is too thick in the agar dilution method?

    <p>Smaller inhibition zones</p> Signup and view all the answers

    Why are media supplements or different media required to obtain good growth and reliable susceptibility profiles for bacteria?

    <p>To enhance bacterial growth and obtain accurate susceptibility profiles</p> Signup and view all the answers

    Which organization is responsible for publishing and updating standards related to susceptibility testing methods?

    <p>Clinical and Laboratory Standards Institute (CLSI)</p> Signup and view all the answers

    What is the purpose of the growth control in the broth dilution method procedure?

    <p>To ensure no bacteria grow in the absence of antimicrobial agents</p> Signup and view all the answers

    Why are susceptibility tests not performed on bacteria that are predictably susceptible to commonly used antimicrobial agents?

    <p>To avoid unnecessary testing</p> Signup and view all the answers

    Why is it important for clinical laboratories to be aware of the antimicrobial agents appropriate for testing?

    <p>To ensure accurate results in susceptibility testing</p> Signup and view all the answers

    When is it necessary to perform antimicrobial susceptibility testing on bacteria according to the text?

    <p>When the bacteria are isolated from blood cultures</p> Signup and view all the answers

    What is the significance of maintaining awareness of the reliability of different test systems for detecting antimicrobial resistance?

    <p>To prevent misinterpretation of susceptibility profiles</p> Signup and view all the answers

    Why would Escherichia coli isolated from stool not undergo susceptibility testing?

    <p>Because they are normal inhabitants of the lower gastrointestinal tract</p> Signup and view all the answers

    In the broth dilution method, what is the purpose of the sterility control?

    <p>To ensure there is no bacterial contamination in the antimicrobial suspension</p> Signup and view all the answers

    Which factor is NOT considered when determining whether antimicrobial susceptibility testing is warranted?

    <p>The host's immune response</p> Signup and view all the answers

    In which scenario would viridans group streptococci not undergo routine susceptibility testing?

    <p>When isolated from throat specimens</p> Signup and view all the answers

    Why would coagulase-negative staphylococci isolated from multiple blood cultures be subjected to susceptibility testing?

    <p>To ensure appropriate treatment for the infection</p> Signup and view all the answers

    What is the primary advantage of breakpoint panels?

    <p>They can test numerous drugs on a single panel</p> Signup and view all the answers

    How is an MIC test performed using an agar-dilution method?

    <p>By spotting antimicrobial solutions onto cooled agar in Petri dishes</p> Signup and view all the answers

    What happens if the lactamase test result is negative?

    <p>The isolate is reported as susceptible</p> Signup and view all the answers

    Why is MUELLER-HINTON AGAR recommended for testing aerobic isolates?

    <p>It can be supplemented with sheep's blood or other nutrients</p> Signup and view all the answers

    What is the primary disadvantage of breakpoint panels?

    <p>A precise MIC is not obtained</p> Signup and view all the answers

    What is the purpose of spot-inoculating test bacteria onto agar plates in an MIC test?

    <p>To ensure even distribution of bacteria on the plate</p> Signup and view all the answers

    What should be done if there is doubt about the validity of the results in the broth microdilution method?

    <p>Results should not be reported and the test should be repeated</p> Signup and view all the answers

    What is a shortcoming of the broth microdilution MIC method mentioned in the text?

    <p>Inability to produce a consistent penicillin MIC for staphylococci</p> Signup and view all the answers

    What does 'breakpoint' refer to in the context of antimicrobial agents?

    <p>A concentration corresponding to a specific MIC breakpoint</p> Signup and view all the answers

    What does it indicate if there is no growth in either well when two concentrations are tested?

    <p>Susceptible isolate</p> Signup and view all the answers

    When is an isolate considered resistant based on its penicillin MIC value?

    <p>$0.25$ μɡ/mL or higher</p> Signup and view all the answers

    What should be done with penicillin MICs of $0.06$ to $0.12$ μɡ/mL in relation to an induced β-lactamase test?

    <p>Induced β-lactamase test should be performed</p> Signup and view all the answers

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