Infectious Disease
Sepsis and empiric therapy
Recognize sepsis early and give broad-spectrum antibiotics within one hour for shock, after cultures when it does not delay treatment. De-escalate based on culture data; treating colonization (asymptomatic bacteriuria, sputum grown from a colonized airway) is a classic trap.
Focused syndromes
S. aureus bacteremia requires repeat cultures, echocardiography, and source control; it is not a contaminant when drawn from two sites. Infective endocarditis is diagnosed by the Duke criteria. For suspected bacterial meningitis, give dexamethasone with or before the first antibiotic dose; add ampicillin when Listeria is a concern (older adults, immunocompromised, pregnancy).
Mycobacteria and HIV
Suspect tuberculosis with apical cavitary disease, and place in airborne isolation; IGRA and PPD cannot distinguish latent from active disease. Latent TB regimens include 4 months of rifampin. Screen everyone for HIV at least once; start antiretroviral therapy regardless of CD4 count, and give prophylaxis for Pneumocystis under CD4 200 and Mycobacterium avium under 50.
C. difficile and stewardship
Diagnose with stool toxin/PCR in symptomatic patients only; oral vancomycin or fidaxomicin is first line, and avoid antimotility agents. Obtain antibiotic allergy histories carefully - many patients labeled penicillin-allergic can safely receive beta-lactams, which improves outcomes.
Worked example
Two sets of blood cultures grow S. aureus in a patient with a new dialysis catheter and fever. This is true bacteremia: remove the catheter, obtain repeat cultures, and get a transesophageal echocardiogram.