Antimicrobial Susceptibility Testing
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Questions and Answers

What type of antimicrobial drugs are synthesized by chemical procedures in the laboratory?

  • Natural products
  • Antibiotics
  • Synthetics (correct)
  • Semisynthetic antibiotics

    • What is the purpose of Antimicrobial Susceptibility Testing?

  • To prescribe antibiotics
  • To determine the side effects of antibiotics
  • To detect antimicrobial resistance (correct)
  • To determine the cost of antibiotics

    • Why is it important to determine the best type of antibmicrobial to be used for a particular microorganism?

  • Because it is a new trend
  • Because it is costly
  • Because it is a physician's preference
  • Because microorganisms are able to acquire and express resistance to antimicrobial agents (correct)

    • What is the name of the microbiological growth medium commonly used for antibiotic susceptibility testing, specifically disk diffusion tests?

    <p>Mueller Hinton Agar</p> Signup and view all the answers

    What does MIC stand for?

    <p>Minimal Inhibitory Concentration</p> Signup and view all the answers

    How is the zone of inhibition determined?

    <p>By measuring the diameter of the obvious absence of growth around the antimicrobial disk</p> Signup and view all the answers

    What is the primary mechanism of action of penicillin?

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

    Which of the following antimicrobials is effective against gram-positive bacteria?

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

    What is the term for antimicrobials that are effective against both gram-positive and gram-negative bacteria?

    <p>Broad-spectrum</p> Signup and view all the answers

    What is the primary mechanism of action of rifampicin?

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

    Which of the following is an example of a semisynthetic antimicrobial?

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

    What is the term for antimicrobials that are derived from microorganisms?

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

    What is the primary purpose of antimicrobial susceptibility testing?

    <p>To determine which antimicrobials will inhibit the growth of the microorganism causing a specific infection</p> Signup and view all the answers

    What is the significance of a large zone of inhibition in a Kirby Bauer Chart?

    <p>The microorganism is susceptible to the antibiotic</p> Signup and view all the answers

    What is the clinical implication of a susceptible result in antimicrobial susceptibility testing?

    <p>The antibiotic is likely to be effective in treating the infection</p> Signup and view all the answers

    What is the mechanism of action of penicillin?

    <p>Inhibiting the synthesis of the bacterial cell wall</p> Signup and view all the answers

    What is the significance of an intermediate result in antimicrobial susceptibility testing?

    <p>The antibiotic may be effective in treating the infection, but the outcome is uncertain</p> Signup and view all the answers

    What is the purpose of comparing the zone size of inhibition to a standard Kirby Bauer Chart?

    <p>To determine the susceptibility of a microorganism to an antibiotic</p> Signup and view all the answers

    Study Notes

    Antimicrobial Drugs

    • Synthetics are antimicrobial drugs synthesized by chemical procedures in the laboratory, examples include Sulfonamides and quinolones.
    • The use of antimicrobials involves the prescription of a physician, who must ensure the prescribed drug is specific for a particular microorganism causing the disease.

    Antimicrobial Susceptibility Testing

    • It is a laboratory procedure to detect antimicrobial resistance.
    • The most common antimicrobial susceptibility test is the Disk Diffusion (Kirby Bauer Method).
    • Sterile disks are impregnated with the Minimal Inhibitory Concentration (MIC) of an antibiotic to determine the sensitivity or resistance of a bacterium to an antimicrobial.
    • Mueller Hinton Agar is a microbiological growth medium used for antibiotic susceptibility testing, specifically disk diffusion tests.

    Minimal Inhibitory Concentration (MIC)

    • MIC refers to the least concentration of an antibiotic that inhibits visible bacterial growth.
    • The zone of inhibition is determined by measuring the diameter of the obvious absence of growth around the antimicrobial disk.

    Antimicrobial Classification

    • Antimicrobials can be classified into three categories: Antibiotics/Antibacterial, Semisynthetic, and Synthetic.
    • Antibiotics/Antibacterial are derived from microorganisms, examples include Penicillin and Streptomycin.
    • Semisynthetic are chemically derived from antibiotic, example is Ampicillin from Penicillin.

    Mechanism of Action

    • Inhibition of Cell Wall Synthesis: Penicillin, Ampicillin, Bacitracin, Ristocetin, Vancomycin, Cephalosporin, and Cycloserine.
    • Inhibition of Protein Synthesis: Chloramphenicol, Erythromycin, Tetracycline, Streptomycin, Gentamycin, Lincomycin, Clindamycin, and Aminoglycosides.
    • Injury to Cell Membrane: Amphotericin B, Polymyxin B, Tyrocidin, and Garamicidin S.
    • Inhibition of Nucleic Acid Synthesis: Rifampicin, Quinolones, Sulfonamides, and Trimethoprim.

    Kirby Bauer Chart

    • The chart is used to compare the zone of inhibition of different antibiotics.
    • The zone size of one drug cannot be compared to the zone size of another.

    Antimicrobial Susceptibility Testing Procedure

    • Plate preparation: 1 medium → 2-8 discs.
    • Incubate for 37°C for 18-24 hours.
    • Measure the zone of inhibition: large zone = SUSCEPTIBLE, small zone = RESISTANT.

    QFR (Quick Facts and Review)

    • Purpose of antimicrobial susceptibility test: to determine which antimicrobials will inhibit the growth of the bacteria or fungi causing a specific infection.
    • Clinical implications of a Resistant, Intermediate, and Susceptible result:
      • Susceptible: high likelihood of therapeutic success.
      • Intermediate: uncertain therapeutic effect.
      • Resistant: high likelihood of therapeutic failure.
    • Mechanism of penicillin: inhibition of cell wall synthesis.

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    Description

    Learn about antimicrobial compounds, antibiotics, and their effects on microorganisms. Understand the differences between narrow-spectrum and broad-spectrum antimicrobials and their effectiveness against various types of microorganisms.

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