Clinical meaning
Antibiotic stewardship at the clinician prescriptive level requires deep understanding of resistance mechanisms, pharmacokinetic/pharmacodynamic (PK/PD) optimization, and evidence-based prescribing. Key resistance mechanisms include: ESBL-producing Enterobacterales (plasmid-mediated CTX-M enzymes hydrolyzing third-generation cephalosporins), carbapenem-resistant Enterobacterales (CRE via KPC, NDM, OXA-48 enzymes), MRSA (mecA gene encoding PBP2a with reduced beta-lactam affinity), and vancomycin-resistant Enterococcus (vanA/vanB gene clusters). PK/PD targets drive dosing: time-dependent antibiotics (beta-lactams) target fT>MIC >40-70%, concentration-dependent antibiotics (aminoglycosides) target Cmax/MIC >10, and AUC-dependent antibiotics (vancomycin, fluoroquinolones) target AUC/MIC ratios. The clinician must select empiric therapy based on local antibiograms, optimize dosing using PK/PD principles, de-escalate based on culture data, determine appropriate duration, and implement stewardship quality metrics.
Diagnosis & workup
Diagnostics & workup: - Order appropriate cultures with susceptibility testing before empiric therapy - Interpret antibiogram data to guide empiric prescribing for the institution - Order rapid diagnostic panels (BCID, respiratory panels) when available for faster pathogen identification - Order therapeutic drug monitoring: vancomycin AUC/MIC (target 400-600), aminoglycoside peak/trough - Order procalcitonin for antibiotic initiation and de-escalation decisions - Interpret MIC breakpoints and CLSI susceptibility categories (S, I, R) for dosing decisions - Order MRSA nasal swab PCR to guide vancomycin de-escalation (NPV >95%) - Order beta-D-glucan and galactomannan for invasive fungal infection workup when needed