Antibiotics

Step 3 usually tests syndrome-based empiric therapy and escalation/de-escalation logic.

Syndrome	Typical Empiric Coverage	Notes
Community-acquired pneumonia outpatient	Amoxicillin, doxycycline, or macrolide depending risk/local resistance	Add broader coverage if comorbidities.
CAP inpatient non-ICU	Beta-lactam + macrolide or respiratory fluoroquinolone	Assess severity and QT risks.
Severe pneumonia	Beta-lactam + macrolide/fluoroquinolone; add MRSA/Pseudomonas coverage if risk	Culture before antibiotics if no delay.
UTI uncomplicated	Nitrofurantoin, TMP-SMX, fosfomycin	Check pregnancy/renal function.
Pyelonephritis	Ceftriaxone initially or fluoroquinolone if appropriate	Admit if septic, pregnant, vomiting, obstructed.
Cellulitis nonpurulent	Strep coverage such as cephalexin	Add MRSA coverage if purulent/risk factors.
Meningitis adult	Vancomycin + ceftriaxone; add ampicillin if older/immunocompromised/pregnant	Do not delay antibiotics for LP if CT needed first.
Intra-abdominal infection	Gram-negative + anaerobe coverage	Source control matters.
Neutropenic fever	Anti-pseudomonal beta-lactam	Medical emergency.

Classic Organism Associations

Animal bite: Pasteurella → amoxicillin-clavulanate.
Diabetic foot: polymicrobial; cover gram-positive, gram-negative, anaerobes depending severity.
C. difficile: oral vancomycin or fidaxomicin for typical initial disease.
MRSA skin abscess: incision and drainage; add antibiotics when systemic signs/risk factors.