Evaluation of some commercial media for the cultivation and enumeration of Clostridium perfringens from the chick intestine.

Four commercial media marketed for the detection and enumeration of Clostridium perfringens were found to adequately support the growth of a pure culture (ATCC 13124) of this species but enumeration of colony-forming units was difficult on Clostrisel and lecithin-lactose-agar base (LLA) media. Colonies of C. perfringens on LLA had typical opalescent zones, a distinctive feature that can aid in presumptive identification. Colonies on sulfite-polymyxin-sulfadiazone and tryptose-sulfite-neomycin (TSN) agar media were morphologically similar but black colonies were observed on TSN incubated at 46 C. Extreme difficulty was encountered in enumerating enteric bacteria from the chick intestine on Clostrisel medium because of the pinpoint size of the colonies and on LLA because of the opacity of the medium. Morphological characteristics of bacteria picked from colonies which formed after these media had been inoculated with chick intestinal contents were in sharp contrast to those of the pure culture of C. perfringens. Numbers of colony-forming units were higher than documented levels of C. perfringens in the intestine of chicks. These observations led to the conclusion that these formulations are inadequate for the selective cultivation and enumeration of this bacterial species from the intestine of healthy chicks, unless used in combination with further tests for specific identification.