questions 4

Aminoglycosides

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Topic updated on 01/20/17 8:23pm

 
Overview of Antibiotic Mechanisms
 
Introduction
  • Classification
    • antibiotic
      • anti-ribosomal 
        • anti-30S ribosomal subunit
          • aminoglycosides
  • Drugs
    • gentamicin
    • neomycin
    • amikacin
    • tobramycin
    • streptomycin
Mechanism
  • Action
    • bactericidal
    • binds to 30S ribosomal subunit 
      • inhibit formation of initiation complex 
      • Aminoglycosides inhibit initiAtion
      • cause misreading of mRNA
    • accumulates inside bacteria via O2-dependent uptake
      • cannot be used against anaerobes
      • "aminO2glycoside"
  • Resistance
    • via modification by acetylation, adenylation, or phosphorylation 
    • Aminglycoside resistance is by Acetylation
Uses
  • Severe infections with Gram-negative rods
    • aerobes only
    • synergistic with β-lactam antibiotics
  • Gentamicin
    • most widely used
    • nosocomial infections
  • Neomycin
    • toxic
    • topically for skin infections
    • bowel surgery
  • Amikacin
    • broadest spectrum
    • nosocomial infections
  • Tobramycin
    • Pseudomonas aeruginosa
  • Streptomycin
    • oldest aminoglycoside
    • resistance is common
Adverse effects
  • Nephrotoxicity
    • especially when used with cephalosporins
  • Ototoxicity 
    • especially when used with loop diuretics
  • Avoid in pregnancy
    • teratogen
    • ototoxicity
  • Neuromuscular block in very high doses


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(M1.MC.3) You are treating a neonate with meningitis using ampicillin and a second antibiotic, X, that is known to cause ototoxicity. What is the mechanism of antibiotic X? Topic Review Topic

1. It binds the 50S ribosomal subunit and inhibits peptidyltransferase
2. It binds the 50S ribosomal subunit and inhibits formation of the initiation complex
3. It binds the 30s ribosomal subunit and inhibits formation of the initiation complex
4. It binds the 30s ribosomal subunit and reversibly inhibits translocation
5. It binds the 50s ribosomal subunit and reversibly inhibits translocation

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