Cultural and physiological characteristics and antimicrobial susceptibility of Clostridium botulinum isolates from foodborne and infant botulism cases.

Isolates Clostridium botulinum from foodborne and infant botulism cases in the United States were compared on the basis of toxigenicity, cultural and biochemical characteristics, metabolic products, and susceptibility to antimicrobial agents. Seventy-eight strains, including 42 from foodborne and 36 from infant botulism sources, were examined. Cultures on anaerobic blood agar exhibited circular, spindle, and rhizoid (medusa head) colonies. Overall, the characteristics of isolates from foodborne and infant botulism cases were quite similar. We concluded that it was not possible to differentiate C. botulinum isolates associated with foodborne botulism from those recovered from infant botulism cases. All of the 78 strains produced an unidentified indole derivative(s), detected with paradimethylaminocinnamaldehyde reagent, and hydrocinnamic acid, detected by gas-liquid chromatography; all exhibited a high degree of resistance to cycloserine, sulfamethoxazole, and trimethoprim. These characteristics should prove to be useful in the isolation and identification of C. botulinum from mixed microbial populations.