Core41: Principles of antimicrobial treatment - empirical, targeted and prophylactic therapy

🦠 High-yield / 要点：Antimicrobial treatment can be empirical before pathogen identification, targeted after results, or prophylactic to prevent infection.

Main treatment strategies / 主な治療戦略

Strategy	Meaning	Key point
Empirical therapy	Treatment before exact pathogen is known	Used early, especially in severe infection
Targeted therapy	Treatment after test results identify pathogen	Prefer narrow-spectrum antibiotic when possible
Prophylactic therapy	Prevention/suppression before infection manifests	Used in defined high-risk situations

Empirical therapy / 経験的治療

• Started before blood/culture results are available.
• Choice depends on:
  • Likely pathogens.
  • Severity of disease.
  • Comorbidities.
  • Antibiotic kinetic parameters.
  • Local resistance patterns/previous experience.
• Examples:
  • Levofloxacin for community-acquired pneumonia.
  • Ceftriaxone + metronidazole, piperacillin-tazobactam, or carbapenems for surgical peritonitis.
  • Ceftriaxone or cefotaxime for bacterial meningitis.
  • Amoxicillin-clavulanate or cephalosporins for acute sinusitis.
  • Penicillin V for tonsillitis follicularis.

Targeted therapy / 標的治療

• Given after pathogen is known.
• Narrow-spectrum therapy is preferred when possible.
• Examples:
  • Benzathine penicillin for Treponema pallidum.
  • Vancomycin for MRSA; flucloxacillin for MSSA.
  • Ceftriaxone for Neisseria meningitidis.
  • Oral vancomycin, metronidazole, or fidaxomicin for C. difficile.

Prophylactic therapy / 予防的治療

• Prevents infection before it occurs or manifests.
• Examples:
  • Cefazolin for orthopedic surgery prophylaxis.
  • Amoxicillin-clavulanate for abdominal surgical prophylaxis.
  • Rifampin or ciprofloxacin for close contacts of meningococcal infection.
  • Isoniazid for tuberculosis contacts.
  • Nitrofurantoin for recurrent UTI prophylaxis.

Remember / 覚え方

• Empirical = before results
• Targeted = after pathogen known
• Prophylactic = before infection
• De-escalate to narrow spectrum when possible