Antimicrobial Agents Quiz
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Questions and Answers

What is the minimum inhibitory concentration (MIC)?

  • The concentration needed to kill 99.9% of the original inoculum
  • The concentration that is many dilutions higher than MBC for bacteriostatic agents
  • The concentration needed for visible growth of a microorganism to be inhibited (correct)
  • The concentration at which beta-lactamase is produced by bacteria

    • Why are penicillins used mainly to treat Gram-positive bacterial infections?

  • Most staphylococci are resistant to benzylpenicillin
  • They have a poor spectrum of activity
  • They are resistant to beta-lactamases (correct)
  • They are lipids soluble

    • Why is benzylpenicillin given by injection rather than orally?

  • It has a poor spectrum of activity
  • It is inactivated by gastric acid (correct)
  • It has a high MIC
  • It is lipids soluble

    • Which penicillin is effective against beta-lactamase producing staphylococci?

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

    What is the main reason ampicillin is rarely used now?

    <p>It is inactivated by beta-lactamase</p> Signup and view all the answers

    Why is amoxicillin often given in combination with clavulanic acid?

    <p>To extend the spectrum of activity</p> Signup and view all the answers

    What is a key structural difference between human cells and bacterial cells?

    <p>Human cells have a membrane-bound nucleus while bacterial cells do not.</p> Signup and view all the answers

    Which type of bacteria has a poorly-defined cell wall and does not hold the Gram stain?

    <p>Atypical bacteria</p> Signup and view all the answers

    What is the main purpose of the Gram stain in classifying micro-organisms?

    <p>To classify them based on their cell wall characteristics</p> Signup and view all the answers

    Which component of bacterial cells is essential to their survival?

    <p>Peptidoglycan in the cell wall</p> Signup and view all the answers

    What is the difference in staining outcome between typical and atypical bacteria with the Gram stain?

    <p>Typical bacteria stain red/pink, while atypical bacteria remain colorless.</p> Signup and view all the answers

    What characteristic distinguishes most bacterial species classified as Gram-positive from those classified as Gram-negative?

    <p>Color in the Gram stain</p> Signup and view all the answers

    What is the main structural component of bacterial cell walls, essential for their survival?

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

    Which type of bacteria do not hold the Gram stain due to their poorly-defined cell wall?

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

    What is the main purpose of the Gram stain in microbiology?

    <p>To classify microorganisms based on cell wall characteristics</p> Signup and view all the answers

    Why are penicillins primarily used to treat Gram-positive bacterial infections?

    <p>They bind to peptidoglycan in the thick cell walls of Gram-positive bacteria</p> Signup and view all the answers

    What distinguishes most bacterial species classified as Gram-positive from those classified as Gram-negative?

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

    What is the measure of antimicrobial susceptibility that indicates the lowest concentration of an antimicrobial that inhibits bacterial growth?

    <p>MIC (Minimum Inhibitory Concentration)</p> Signup and view all the answers

    Why must the minimum inhibitory concentration (MIC) be exceeded for antibacterial agents to be effective?

    <p>To inhibit the growth of micro-organisms</p> Signup and view all the answers

    What is the main difference between minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC)?

    <p>MIC is higher than MBC for bacteriostatic agents, MBC is higher for bactericidal agents</p> Signup and view all the answers

    Why is ampicillin rarely used now?

    <p>It has low absorption properties</p> Signup and view all the answers

    Why are penicillins like Benzylpenicillin and Phenoxymethylpenicillin given orally?

    <p>They are stable against gastric acid</p> Signup and view all the answers

    Why are the antipseudomonal penicillins, piperacillin and ticarcillin, administered with an aminoglycoside in Pseudomonas septicaemias?

    <p>To create a synergistic effect against Pseudomonas aeruginosa</p> Signup and view all the answers

    Which penicillin is effective against beta-lactamase producing staphylococci?

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

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