empiric therapy

Empiric therapy is used when waiting for definitive diagnostic results (e.g., cultures, PCR, sensitivities) would delay treatment and risk patient deterioration, as in sepsis, meningitis, febrile neutropenia, or severe pneumonia. Selection of empiric agents relies on: the anatomic site of infection (which determines likely pathogens, e.g., E. coli in UTIs, S. pneumoniae in CAP), patient-specific factors (age, immune status, comorbidities, recent hospitalization, prior antibiotic exposure), local antibiograms/resistance patterns, and severity of illness (broader coverage for critically ill patients). Common examples include: community-acquired pneumonia (macrolide or beta-lactam + macrolide), meningitis (vancomycin + ceftriaxone +/- ampicillin for Listeria in high-risk groups), febrile neutropenia (anti-pseudomonal beta-lactam like cefepime or piperacillin-tazobactam), and suspected sepsis (broad-spectrum coverage per Surviving Sepsis Campaign guidelines, ideally within 1 hour). After obtaining cultures BEFORE starting empiric antibiotics (critical teaching point for boards), therapy should be de-escalated once organism and sensitivities are known, narrowing spectrum to reduce resistance, cost, and adverse effects (antibiotic stewardship principle). Boards often test on knowing appropriate empiric regimens for specific infections and understanding the sequence: obtain cultures → start empiric therapy → adjust based on results. Failure to de-escalate is a common source of antibiotic resistance and C. difficile infection.