Infectious Disease & Antimicrobials

Time-dependent killing — efficacy tracks the percent of the dosing interval that free drug stays above the MIC (%fT>MIC); optimized by frequent dosing or extended/continuous infusion.

Concentration-dependent killing — efficacy correlates with peak/MIC (aminoglycosides) and AUC/MIC; both exhibit a postantibiotic effect, supporting once-daily/extended-interval dosing.

Continued suppression of bacterial growth after drug concentrations fall below the MIC; prominent with aminoglycosides and fluoroquinolones, allowing extended dosing intervals.

Optimize antimicrobial use to improve outcomes while minimizing resistance, toxicity, C. difficile, and cost — via appropriate selection, dose, route, de-escalation, and duration.

Bind penicillin-binding proteins (PBPs), inhibiting transpeptidation/cross-linking of peptidoglycan in the bacterial cell wall; bactericidal.

Streptococci, many oral anaerobes, Treponema pallidum (syphilis), and susceptible enterococci; drug of choice for syphilis. Limited by widespread beta-lactamase resistance.