Virulence of clinical and fecal isolates of Clostridium perfringens type A for outbred NMRI mice.

Twelve clinical and 102 fecal isolates from healthy carriers of Clostridium perfringens type A were tested for virulence in juvenile, outbred NMRI mice (intramuscular route). There were marked differences (up to 1,000-fold) in virulence among strains of both groups of isolates. On average, clinical isolates were not more virulent than fecal isolates. Fresh epinephrine (10 micrograms/mouse and given concurrently with bacterial inocula) significantly augmented virulence. The murine model of Hill and Osterhout for experimental gas gangrene yielded reproducible results. Myelosuppressed (cyclophosphamide-pretreated) mice were somewhat more susceptible to C. perfringens as contrasted with mice that had been pretreated with either carrageenan type II or with zymosan. The murine virulence of C. perfringens was enhanced significantly by Escherichia coli.