Antimicrobial Agents Overview
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Antimicrobial Agents Overview

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Questions and Answers

What does selective toxicity ensure in antimicrobial drugs?

  • The drug can cause harm to the beneficial microbes in the body.
  • The drug kills the host while treating the infection.
  • The drug inhibits microbial pathogens with minimal damage to the host. (correct)
  • The drug has no side effects on any organism.

    • What is the therapeutic dose of an antimicrobial drug?

  • The dose at which the drug becomes ineffective.
  • The dose necessary to kill 50% of the pathogenic microbes.
  • The dose required for clinical treatment of an infection. (correct)
  • The highest dose that does not cause any effect.

    • How is the therapeutic index (TI) calculated?

  • TI = ED50 / ED90
  • TI = TD50 / TD10
  • TI = ED50 / TD50
  • TI = TD50 / ED50 (correct)

    • What does a lower therapeutic index indicate?

    <p>A higher risk of adverse effects relative to the therapeutic effect.</p> Signup and view all the answers

    What is the significance of TD50 in the context of antimicrobial drugs?

    <p>It is the dose at which 50% of the population experiences a toxic effect.</p> Signup and view all the answers

    What discovery is credited to Alexander Fleming in 1928?

    <p>The antibacterial properties of Penicillium mold</p> Signup and view all the answers

    Which term describes antibiotics that inhibit bacterial growth rather than killing them?

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

    What is the role of antivirals in treating infections?

    <p>They prevent the virus from multiplying</p> Signup and view all the answers

    What are antiprotozoal drugs specifically designed to target?

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

    Which type of antibiotic is preferred in severe infections for rapid bacterial eradication?

    <p>Bactericidal antibiotics</p> Signup and view all the answers

    Which mechanism is NOT typically associated with bactericidal agents?

    <p>Blocking viral replication</p> Signup and view all the answers

    Which of the following antibiotics was developed through the purification and development work of Howard Florey and Ernst Chain?

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

    Which category of antimicrobial agents specifically targets fungi?

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

    What does the '50S' in 50S ribosomes indicate?

    <p>The sedimentation coefficient measured in Svedbergs</p> Signup and view all the answers

    Which rRNA is contained in the 30S ribosomal subunit?

    <p>16S rRNA</p> Signup and view all the answers

    Which antibiotic is known to block aminoacyl tRNA binding to the A site?

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

    What is a primary mechanism through which aminoglycosides promote protein mistranslation?

    <p>Causing misreading of the genetic code</p> Signup and view all the answers

    Which of the following is a characteristic of aminoglycosides?

    <p>They are considered bactericidal antibiotics.</p> Signup and view all the answers

    Which mechanism is NOT a way bacteria can develop resistance to aminoglycosides?

    <p>Enhanced binding of aminoglycosides to ribosomes</p> Signup and view all the answers

    What action do macrolides and clindamycin have on the ribosome?

    <p>Block the translocation step</p> Signup and view all the answers

    Which of the following correctly matches the ribosomal subunit with its respective rRNA components?

    <p>30S: 16S rRNA and ribosomal proteins</p> Signup and view all the answers

    What is the primary target of cycloserine in the treatment of tuberculosis?

    <p>Cell wall synthesis</p> Signup and view all the answers

    Which class of antibiotics is known to inhibit the binding process in protein synthesis?

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

    Which mechanism of action is associated with sulfonamides?

    <p>Interference with metabolic pathways</p> Signup and view all the answers

    What is the composition of bacterial ribosomes?

    <p>One large and one small subunit</p> Signup and view all the answers

    Which antibiotic class disrupts peptidoglycan cross-linking in bacterial cell walls?

    <p>β-lactams</p> Signup and view all the answers

    What type of antibiotics bind to membrane phospholipids causing leakage?

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

    Antibiotics that interfere with DNA or RNA synthesis are represented by which class?

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

    Which is NOT a mechanism of action for antimicrobial agents?

    <p>Enhancement of gut flora</p> Signup and view all the answers

    What mechanism allows bacteria to resist chloramphenicol?

    <p>Acetylation of chloramphenicol</p> Signup and view all the answers

    Which condition is associated with chloramphenicol toxicity in neonates?

    <p>Gray baby syndrome</p> Signup and view all the answers

    Which type of bacteria are macrolides primarily effective against?

    <p>Respiratory pathogens</p> Signup and view all the answers

    What phenomenon describes the ability of bacteria to resist multiple drugs within the same group?

    <p>Cross-resistance</p> Signup and view all the answers

    Which bacterial group is NOT effectively targeted by macrolides?

    <p>Gram-negative bacilli</p> Signup and view all the answers

    What is a common side effect of chloramphenicol regarding bone marrow function?

    <p>Reversible dose-dependent bone marrow suppression</p> Signup and view all the answers

    Which mechanism contributes to bacterial resistance against macrolides?

    <p>Ribosome binding site alteration</p> Signup and view all the answers

    What is the primary classification of chloramphenicol?

    <p>Bacteriostatic antibiotic</p> Signup and view all the answers

    Study Notes

    Antimicrobial Agents

    • Alexander Fleming discovered the antibacterial properties of Penicillium mold in 1928.
    • Howard Florey and Ernst Chain purified and developed penicillin in the 1940s, leading to its widespread use as an antibiotic.

    Antimicrobial Definitions

    • Antibiotics target bacteria, either killing them (bactericidal) or inhibiting their growth (bacteriostatic).
    • Antivirals target viruses, inhibiting their development and replication.
    • Antiprotozoal drugs target protozoa, single-celled organisms that cause diseases such as malaria and amoebiasis.
    • Antifungals target fungi, either killing them (fungicides) or inhibiting their growth (fungistatics).

    Antimicrobial Mechanisms of Action

    • Bactericidal agents kill bacteria by disrupting cell wall synthesis, damaging cell membranes, or interfering with vital cellular functions.
    • Bacteriostatic agents inhibit bacterial growth, preventing them from multiplying.

    General Characteristics of Antimicrobial Drugs

    • Selective toxicity: Antimicrobial drugs should target microbial pathogens while minimizing harm to the host.
    • Therapeutic dose: The drug level required for clinical treatment of a particular infection.
    • Toxic dose: The drug level at which the agent becomes too toxic for the host.
    • Therapeutic index: The ratio of the toxic dose to the therapeutic dose.

    Antimicrobial Spectrum of Activity

    • Narrow-spectrum antibiotics target a limited range of bacterial species.
    • Broad-spectrum antibiotics target a wider range of bacterial species.

    Protein Synthesis Inhibitors

    • Aminoglycosides bind to the 30S subunit of the bacterial ribosome, causing mismatching between mRNA codons and charged tRNA, leading to protein mistranslation.
    • Chloramphenicol inhibits protein synthesis by binding to the 50S subunit of the bacterial ribosome, blocking peptide bond formation.
    • Macrolides bind to the 50S ribosomal subunit, blocking the translocation step of protein synthesis.
    • Ketolides are a structurally related class of antibiotics to macrolides.

    Aminoglycosides

    • Mechanism of action: Bind to the 30S ribosomal subunit, leading to protein mistranslation.
    • Mechanism of resistance: Decreased accumulation within the bacterium, drug inactivation, and mutations in the ribosome binding site.
    • Spectrum of activity: Broad spectrum, effective against many Gram-positive and Gram-negative bacteria.

    Chloramphenicol

    • Mechanism of action: Binds to the 50S ribosomal subunit, blocking peptidyl transferase.
    • Bacterial resistance: Inactivation of chloramphenicol by bacterial enzymes, and efflux pumps.
    • Side effects: Reversible dose-dependent bone marrow suppression, gray baby syndrome, and neurologic abnormalities.

    Macrolides and Ketolides

    • Mechanism of action: Bind to the 50S ribosomal subunit, blocking the translocation step of protein synthesis.
    • Bacterial resistance: Inhibition of drug entry, enzyme-mediated ribosome binding site alteration, and mutations in the ribosome binding site.
    • Spectrum of activity: Narrow spectrum, effective against specific types of infections, such as respiratory infections.

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    Description

    Explore the history and definitions of various antimicrobial agents, including antibiotics, antivirals, antifungals, and antiprotozoals. This quiz covers key figures like Alexander Fleming and pivotal discoveries in medicine. Test your knowledge on mechanisms of action for these compounds.

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