ROUNDS·
Infectious Disease

Common Antibiotics Guide: CAP, UTI, and Sepsis

A quick orientation to antibiotic classes by clinical syndrome — for understanding, not for prescribing.

By Drug Class

ClassExamplesCommon use
PenicillinsAmoxicillin, co-amoxiclavRespiratory, UTI
CephalosporinsCeftriaxone, cefalexinBroad-spectrum, meningitis
MacrolidesClarithromycin, azithromycinAtypical pneumonia, penicillin allergy
FluoroquinolonesCiprofloxacinUTI, GI — caution: tendon/QT risk
GlycopeptidesVancomycinMRSA, severe Gram-positive infection
CarbapenemsMeropenemBroad-spectrum, reserved for resistant organisms
AminoglycosidesGentamicinGram-negative; nephrotoxic/ototoxic, monitor levels

This table is for orientation only — doses and exact agent choice vary by local protocol and resistance patterns.

Community-Acquired Pneumonia

Treatment is guided by severity (see the full pneumonia management guide and CURB-65 calculator) — outpatient single-agent therapy for low severity, combination therapy for moderate-severe disease.

Urinary Tract Infection

Uncomplicated lower UTI typically needs a short oral course per local resistance guidance. Pyelonephritis needs a longer course and possibly IV therapy. Catheter-associated UTI should only be treated if symptomatic.

Sepsis

The Hour-1 bundle calls for broad-spectrum empirical antibiotics within one hour of recognition (see the qSOFA calculator for screening) — choice depends on the suspected source and local resistance patterns, then de-escalates once cultures return.

A Note on Stewardship

Antibiotic choice and dosing should always follow local antimicrobial guidelines. Resistance patterns vary significantly by region and change over time — this page is for orientation, not prescribing.

Frequently Asked Questions

Why does antibiotic choice vary by region?

Local resistance patterns (antibiograms) differ by hospital and region, so the empirical agent most likely to work in one area may not be ideal in another.

What's the difference between empirical and targeted therapy?

Empirical therapy is started before culture results are known, based on the most likely pathogens. Once cultures and sensitivities return, therapy is narrowed (de-escalated) to a targeted agent.

Why is vancomycin reserved rather than first-line?

Reserving glycopeptides and other broad-spectrum agents for confirmed or strongly suspected resistant organisms helps limit the development of further antibiotic resistance.