Pharmaceutical Microbiology: Antibiotics Resistance
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Questions and Answers

What is the mechanism of resistance to beta-lactam antibiotics?

  • Efflux pumps
  • Enzymatic inactivation (correct)
  • Production of aminoglycoside inactivating enzyme
  • Alteration of target site

    • What is the result of the acquisition of mecA gene in MRSA?

  • Alteration of target site
  • PBP2a with high affinity for β-lactams
  • Production of aminoglycoside inactivating enzyme
  • PBP2a with low affinity for β-lactams (correct)

    • What is the mechanism of vancomycin resistance?

  • Enzymatic inactivation
  • Efflux pumps
  • Production of aminoglycoside inactivating enzyme
  • Alteration of target site (correct)

    • What is the effect of efflux pumps on bacterial resistance?

    <p>Increase the elimination of antibiotics</p> Signup and view all the answers

    What is the consequence of antibiotic resistance on healthcare costs?

    <p>Increased healthcare costs</p> Signup and view all the answers

    What is a common misuse of antibiotics?

    <p>Over-prescribing of antibiotics</p> Signup and view all the answers

    What is the effect of antibiotic resistance on morbidity?

    <p>Increased morbidity</p> Signup and view all the answers

    What is the mechanism of resistance to quinolone antibiotics?

    <p>Alteration of DNA gyrase</p> Signup and view all the answers

    What is antimicrobial resistance?

    <p>The ability of microorganisms to survive and reproduce in the presence of antimicrobial agents</p> Signup and view all the answers

    What type of resistance is due to bacterial structural or functional features?

    <p>Intrinsic resistance</p> Signup and view all the answers

    What is an example of intrinsic resistance?

    <p>Gram-negative bacteria are intrinsically resistant to vancomycin</p> Signup and view all the answers

    What is the mechanism of acquired resistance?

    <p>Horizontal Gene Transfer and mutations</p> Signup and view all the answers

    What is cross resistance?

    <p>A single mechanism confers resistance to multiple antimicrobial agents</p> Signup and view all the answers

    What is multiple drug resistance (MDR)?

    <p>Antimicrobial resistance shown by a species of microorganism to at least one antimicrobial drug in three or more antimicrobial categories</p> Signup and view all the answers

    What is an example of intrinsic resistance to metronidazole?

    <p>Aerobic bacteria are intrinsically resistant to metronidazole</p> Signup and view all the answers

    What is the main reason for the emergence of antibiotic resistance?

    <p>The misuse of antibiotics</p> Signup and view all the answers

    What is the mechanism of action of azoles?

    <p>Inhibiting the fungal cytochrome P-450 3-A dependent enzyme 14-alpha demethylase</p> Signup and view all the answers

    What is the effect of azoles on fungal cells?

    <p>Accumulation of toxic intermediate sterols</p> Signup and view all the answers

    Which azole is used to treat Candida albicans?

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

    What is a characteristic of triazole drugs?

    <p>All except Posaconazole are available in injection form</p> Signup and view all the answers

    Why is itraconazole more frequently associated with liver toxicity?

    <p>Because it is more likely to cause liver damage</p> Signup and view all the answers

    What is a characteristic of imidazole azoles?

    <p>They are used to treat dermatophytes</p> Signup and view all the answers

    Why is fluconazole better absorbed from the GIT than itraconazole?

    <p>Because it has a more favorable pharmacokinetic profile</p> Signup and view all the answers

    What is a characteristic of topical azole products?

    <p>They are used to treat superficial fungal infections</p> Signup and view all the answers

    What is one mechanism of resistance where the drug is destroyed?

    <p>Production of inactivating enzymes</p> Signup and view all the answers

    Which type of antibiotics is affected by β-lactamases?

    <p>Penicillins and cephalosporins</p> Signup and view all the answers

    What is the result of modification of the target site?

    <p>Decreased affinity for the antibiotic</p> Signup and view all the answers

    Which of the following is NOT a mechanism of resistance?

    <p>Increased cellular uptake</p> Signup and view all the answers

    What is the result of production of inactivating enzymes?

    <p>Inactivation of antibiotics</p> Signup and view all the answers

    Which enzyme is responsible for inactivating aminoglycosides?

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

    What is the result of increased efflux?

    <p>Decreased accumulation of antibiotics in the cell</p> Signup and view all the answers

    What is an example of a bacterium that exhibits methicillin resistance?

    <p>S. aureus</p> Signup and view all the answers

    What is the purpose of using Anidulafungin and Micafungin?

    <p>To minimize the risk of resistance development</p> Signup and view all the answers

    How is Flucytosine absorbed into fungal cells?

    <p>Via cytosine permease</p> Signup and view all the answers

    What is the effect of Flucytosine on fungal cells?

    <p>It interferes with fungal RNA biosynthesis</p> Signup and view all the answers

    What is the use of Flucytosine?

    <p>To treat systemic Candida spp. or Cryptococcus spp.</p> Signup and view all the answers

    What is the mechanism of action of Griseofulvin?

    <p>It binds to polymerized fungal microtubules</p> Signup and view all the answers

    What is the use of Griseofulvin?

    <p>To treat dermatophytoses of the skin, hair, and nails</p> Signup and view all the answers

    Study Notes

    Antimicrobial Resistance

    • Antimicrobial resistance is the ability of microorganisms to survive and reproduce in the presence of antimicrobial agents that were previously thought to be effective against them.

    Classification of Antibiotic Resistance

    • Intrinsic resistance: due to bacterial structural or functional features, naturally occurring, species or genus specific.
      • Examples: Gram-negative bacteria are intrinsically resistant to vancomycin, aerobic bacteria are intrinsically resistant to metronidazole.
    • Acquired resistance: can take place by two different mechanisms: mutations and horizontal gene transfer.
      • Present only in certain strains of a species or genus.

    Mechanisms of Resistance

    • Modification of the drug: production of enzyme that destroys or deactivates drug.
      • Examples: β-lactamases convert penicillins and cephalosporins into penicilloic and cephalosporic acids.
    • Alteration of the target: alter target of drug so it binds less effectively.
      • Example: methicillin resistance in S. aureus (MRSA) due to the acquisition of mecA gene encodes PBP2a, that has low affinity for all β-lactams.
    • Reduced cellular uptake: slow or prevent entry of drug into the cell.
    • Increased efflux: pump antimicrobial drug out of the cell before it can act.

    Common Misuses of Antibiotics

    • Over-prescribing of antibiotics.
    • Prolonged prophylactic therapy.
    • It is too toxic to be given by injection.

    Mechanism of Action of Antifungal Drugs

    Azoles

    • Inhibit ergosterol synthesis by inhibiting the fungal cytochrome P-450 3-A dependent enzyme 14-alpha demethylase, blocking the demethylation of lanosterol to ergosterol.
      • Accumulation of toxic intermediate sterols.
      • Increased membrane permeability, cell death.

    Triazoles

    • Fluconazole, itraconazole, posaconazole
    • All are orally active, except posaconazole, which is available in injection form.

    Nucleic Acid Synthesis

    • Flucytosine is absorbed into fungal cells via cytosine permease and converted to 5-fluorouracil, which interferes with fungal RNA biosynthesis.
      • Used to treat systemic Candida spp. or Cryptococcus spp. infections.

    Cell Mitosis

    • Griseofulvin is a mitotic inhibitor that binds to polymerized fungal microtubules, inhibiting the de-polymerization, and leading to the failure of the fungal cell replication.
      • Used to treat dermatophytoses of the skin, hair, and nails.

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    Description

    This quiz covers the mechanisms of antibiotics resistance and enumeration of different mechanisms in pharmaceutical microbiology.

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