Core40: Principles of antimicrobial treatment - selective toxicity

🎯 High-yield / 要点：Selective toxicity means antimicrobial drugs target microbial-specific structures/pathways while causing minimal host damage. It is relative, not absolute.

Definition / 定義

• Selective toxicity = ability of an antimicrobial to:
  • Kill microorganisms, or
  • Inhibit microbial growth,
  • While causing minimal/no harm to the host.
• This is the basis for treating infections with acceptable side effects.
• Selective toxicity is relative because human toxicity can still occur.

Sources of selective toxicity / 選択毒性の根拠

Basis	Microbial target	Drug examples
Microbe-specific structure	Peptidoglycan cell wall	β-lactams: penicillins, cephalosporins; vancomycin
Virus-specific enzyme	Reverse transcriptase	Tenofovir, emtricitabine
Metabolic pathway difference	Bacterial folate synthesis	Sulfonamides
Structural difference	Bacterial ribosomes	30S: aminoglycosides, tetracyclines; 50S: macrolides, linezolid, clindamycin

Important examples / 重要例

• Cell wall synthesis inhibitors:
  • Humans do not have peptidoglycan cell walls.
  • β-lactams and vancomycin can selectively target bacteria.
• Folate pathway:
  • Humans obtain folate from diet.
  • Bacteria synthesize folate → sulfonamides inhibit bacterial folate synthesis.
• Ribosome inhibitors:
  • Bacterial ribosomes differ from human ribosomes.
  • Allows selective inhibition of bacterial protein synthesis.

Remember / 覚え方

• Best antimicrobial targets are absent or different in humans
• Cell wall, folate synthesis, bacterial ribosomes = classic selective toxicity
• Selective toxicity is relative → adverse effects still possible