Physiological characteristics ofClostridium bifermentans selectively isolated from California desert tortoise

A selective agar medium containing cycloserine (250 mg/L), sulfamethoxazole (76 mg/L), and trimethoprim (4 mg/L) was used for isolation ofClostridium bifermentans from the intestinal contents of California desert tortoise. Typical lecithinase positive colonies that appeared on the plates, were biochemically characterized with the API 20A System and a conventional procedure. The susceptibility of the isolates to 12 antimicrobial agents was determined by the broth microtitration technique using the ANA MIC System.C. bifermentans strains were shown to be highly susceptible to cefoxitin, cefotetan, ceftizoxime, cefotaxime, chloramphenicol, clindamycin, penicillin, metronidazole, piperacillin, ticarcillin, and mezlocillin. Less than 10% of the isolates exhibited resistance to tetracycline. All strains were found to be highly resistant to cycloserine, sulfamethoxazole, and trimethoprim. The GLC analysis of the culture supernatants for volatile fatty acids revealed the presence of formic, acetic, isobutyric, butyric, isovaleric, and isocaproic acids.