Pharmacotherapy of Infectious Diseases and Antimicrobial Stewardship
Core concepts
Know the pharmacology of major antibiotic classes (beta-lactams, glycopeptides, aminoglycosides, fluoroquinolones, macrolides), their spectrum and key toxicities. Understand antimicrobial stewardship: right drug, right dose, right duration, de-escalation based on culture, and avoidance of unnecessary broad-spectrum agents. Time-dependent killing (beta-lactams) requires extended or continuous infusion for optimisation; concentration-dependent killing (aminoglycosides) favours once-daily dosing. Know that vancomycin requires AUC-guided monitoring.
Traps in questions
A frequent trap is treating asymptomatic bacteriuria - generally not indicated except in pregnancy or before urological procedures. Another is extending surgical prophylaxis beyond 24 hours (no benefit, more resistance). Questions may confuse colonisation with infection. Also watch for fluoroquinolone restrictions (tendinopathy, QT prolongation) and the fact that aminoglycosides are nephrotoxic and ototoxic.
Worked rule of thumb
Use the "culture before, narrow after" rule: obtain cultures before the first dose, start empirical broad therapy if severe, then de-escalate within 48–72 hours once susceptibilities return. For a stable patient with a positive urine culture but no symptoms, the correct action is no antibiotic - document and monitor.
Stewardship metrics
Know that defined daily doses and days of therapy are stewardship metrics, and that allergy labels (especially penicillin) should be verified because most patients labelled penicillin-allergic can tolerate beta-lactams after assessment.