Morphology: Large gram-positive rod, spore-forming (spores rarely seen in clinical specimens), strictly anaerobic. Double-zone β-hemolysis on blood agar. Reverse CAMP test positive.
Typical drugs
- #1Penicillin G— **3–4 million units IV q4h** — drug of choice for myonecrosis (gas gangrene).
- #2Clindamycin— **900 mg IV q8h — add to PCN** for toxin suppression. Critical in invasive disease.
- #3Metronidazole— PCN alternative for true allergy. Active vs all clostridia.
- #4Meropenem— Empiric coverage if mixed infection / unclear etiology.
Empiric therapy when resistant
C. perfringens remains universally susceptible to penicillin. Clindamycin added not for spectrum but for toxin suppression (α-toxin and θ-toxin are responsible for tissue destruction). Imipenem/meropenem also reliable. Resistance is not a clinical concern.
Resistance notes
No clinically significant resistance to first-line agents.
Common syndromes
Pearls
Gas gangrene = clostridial myonecrosis — fulminant infection of muscle following trauma, surgery, or hematogenous spread (esp from colorectal malignancy). Crepitus + severe pain out of proportion + rapid progression. α-toxin (lecithinase) causes massive tissue destruction. Treatment is surgical debridement + PCN + clindamycin (clinda blocks toxin synthesis). Hyperbaric oxygen controversial — case-by-case. Food poisoning is a separate, self-limited GI illness from preformed enterotoxin (heat-stable form C, heat-labile form A) — no antibiotics needed.
References
- IDSA Skin and Soft-Tissue Infection Guidelines (2014)
- Stevens — Necrotizing Soft-Tissue Infections, NEJM (2017)