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Classes of Antibiotics

Jun 8, 2024

Classes of Antibiotics

Overview

The lecture introduces various classes of antibiotics, how they work, and what type of bacteria they target. A mnemonic “Antibiotics Can Protect The Queen’s Men, Servants, and Guards” is used to remember the different classes of antibiotics.

Aminoglycosides (A)

  • Examples: Streptomycin, Gentamicin
  • Target: Gram-negative bacteria
  • Mechanism: Inhibits protein synthesis by targeting the 30S ribosomal subunit
    • Bacteria: 50S and 30S subunits
    • Humans: 60S and 40S subunits

Cephalosporins (C)

  • Examples: Cefazolin, Cefadroxil
  • Target: Both gram-positive and gram-negative bacteria
  • Mechanism: Inhibits cell wall synthesis by breaking bonds between protein links holding sugar molecules together

Penicillins (P)

  • Examples: Penicillin G, Ampicillin
  • Target: Initially gram-positive, later versions like Ampicillin target both gram-positive and gram-negative bacteria
  • Mechanism: Inhibits cell wall synthesis by breaking peptide bonds in the cell wall structure
  • Resistance: Development of beta-lactamase enzymes by bacteria, leading to newer forms like Methicillin, but resistance (MRSA - Methicillin-Resistant Staphylococcus Aureus) still occurs

Tetracyclines (T)

  • Examples: Tetracycline, Doxycycline
  • Target: Both gram-positive and gram-negative bacteria
  • Mechanism: Inhibits protein synthesis by targeting the 30S ribosomal subunit

Quinolones and Fluoroquinolones (Q)

  • Examples: Ciprofloxacin
  • Target: Both gram-positive and gram-negative bacteria
  • Mechanism: Inhibits DNA replication by blocking the enzyme topoisomerase
    • DNA must unwind to replicate, topoisomerase aids this process

Macrolides (M)

  • Examples: Erythromycin
  • Target: Gram-positive bacteria
  • Mechanism: Inhibits protein synthesis by targeting the 50S ribosomal subunit

Sulfonamides (S)

  • Examples: Sulfamethoxazole
  • Target: Both gram-positive and gram-negative bacteria
  • Mechanism: Inhibits folate synthesis
    • Bacteria can make their own folate; humans get folate from their diet

Glycopeptides (G)

  • Examples: Vancomycin
  • Target: Gram-positive bacteria
  • Mechanism: Inhibits cell wall synthesis

Summary

  • Antibiotics target specific bacterial structures/functions not found in human cells
  • Resistance can occur, necessitating the development of new antibiotics

Full transcript