Abstract
Seventy-four strains of Bifidobacterium were isolated from the feces of three strains of experimental rats, F 344/Jcl, Jcl: Wistar and Slc: Wistar, obtained from two different breeders (Japan Clea; Jcl, and Japan SLC; Slc), by using a non-selective medium (BL agar) and a selective medium (BS agar). Species of these isolates were identified by the sugar fermentation test and DNA-DNA hybridization. All of the 45 strains isolated from F344/Jcl and Jcl: Wistar were identified as Bifidobacterium pseudolongum subsp. globosum. On the other hand, all of the 29 the strains obtained from Slc: Wistar were identified B. animalis. Since B. animalis isolated from Slc: Wistar had not grown on the BS agar, an improved selective medium for the isolation and enumeration of Bifidobacterium from experimental rats was developed. TOS medium, used for enumeration of Bifidobacterium in dairy products, was improved by the addition of cephalothin, phosphomycin, sodium propionate and lithium chloride as selective agents, and by correcting pH of the medium. By using this selective medium, the number of Bifidobacterium in the feces of rats was elucidated 106-8 per gram.
