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Antimicrobial Drugs and Mechanisms in Microbiology

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Termini in questo insieme (20)

  • What is the goal of antimicrobial chemotherapy?
    To administer a drug to an infected person that destroys the infective agent without harming the host's cells.
  • Who discovered penicillin and what is its significance?
    Alexander Fleming discovered penicillin, the first true antibiotic released from Penicillium mold.
  • What are beta-lactam antibiotics and their mechanism of action?
    Beta-lactams contain a beta-lactam ring and inhibit enzymes that cross-link NAM subunits in bacterial cell walls, causing cell lysis.
  • How do semisynthetic antibiotics differ from natural antibiotics?
    Semisynthetics are chemically altered natural antibiotics that are more effective, longer lasting, or easier to administer.
  • Name an antibiotic that interferes with mycolic acid formation and its target diseases.
    Isoniazid disrupts mycolic acid formation in mycobacteria, used to treat tuberculosis and leprosy.
  • How do echinocandins inhibit fungal cell wall synthesis?
    They inhibit the enzyme that synthesizes glucan, a key fungal cell wall polysaccharide, causing cell rupture.
  • Why can some antibiotics selectively inhibit bacterial protein synthesis?
    Because prokaryotic ribosomes are 70S, different from eukaryotic 80S ribosomes, allowing selective targeting.
  • What is the role of mupirocin in protein synthesis inhibition?
    Mupirocin binds isoleucyl-tRNA synthetase, preventing isoleucine loading on tRNA in Gram-positive bacteria.
  • How do polyenes like amphotericin B disrupt fungal membranes?
    They bind to ergosterol in fungal membranes, forming pores that disrupt membrane integrity.
  • What is the mechanism of action of polymyxin antibiotics?
    Polymyxins disrupt cytoplasmic membranes of Gram-negative bacteria, causing leakage and cell death.
  • How do sulfonamides act as antimetabolic agents?
    They inhibit folic acid synthesis by competing with para-aminobenzoic acid (PABA), blocking nucleotide production.
  • What is the therapeutic index (TI) and why is it important?
    TI is the ratio of toxic dose to effective dose; a higher TI means a safer drug with a wider margin of safety.
  • What is the Kirby-Bauer test used for?
    It measures antibiotic susceptibility by observing zones of inhibition around antibiotic discs on bacterial lawns.
  • What does the minimum inhibitory concentration (MIC) test determine?
    The smallest concentration of a drug that visibly inhibits bacterial growth.
  • Why is selective toxicity important in antimicrobial drugs?
    It ensures the drug targets pathogens without harming host cells by exploiting differences in structure or metabolism.
  • What causes bacterial resistance to penicillin?
    Production of penicillinase (beta-lactamase) enzymes that destroy the beta-lactam ring of penicillin.
  • List two mechanisms bacteria use to resist antimicrobial drugs.
    Producing enzymes that deactivate drugs and pumping drugs out of the cell before they act.
  • What is the difference between narrow-spectrum and broad-spectrum antibiotics?
    Narrow-spectrum antibiotics target a limited group of bacteria; broad-spectrum target many types.
  • How can misuse of antibiotics lead to superinfections?
    Broad-spectrum antibiotics kill normal flora, reducing microbial antagonism and allowing resistant pathogens to proliferate.
  • What is the significance of reverse transcriptase inhibitors in antiviral therapy?
    They block the enzyme HIV uses for replication, without harming humans who lack reverse transcriptase.