Selective medium for Corynebacterium kutscheri and localization of the organism in mice and rats

A new selective medium for isolation of Corynebacterium kutscheri (CK) from animals suffering subclinical infection was made by adding furazolidone, nalidixic acid and corimycin to the heart infusion agar base, this being named FNC agar. The FNC agar inhibited the growth of gram-negative rods, Pseudomonas aeruginosa, Proteus sp. and gram-positive cocci but did not affect the growth of CK. When this medium was used to isolate CK from the oral cavity and cecal contents of mice and rats, two of 6 conventional mouse colonies and three of 8 conventional rat colonies were found to be infected, with isolation of the organism from 19 mice and 12 rats in total. The animals showed neither clinical signs nor lesions, but the antibody was positive in 11 mice and 10 rats. In mice and rats inoculated orally with 4 x 10(8) and 1 x 10(9) organisms, respectively, CK was isolated for 20 weeks post-inoculation by use FNC agar. The isolation rate of the organism was the highest in the oral cavities of both inoculated mice and rats, and also in the submaxillary lymph nodes of the inoculated rats. The organism was also recovered from the cecal contents of more than half of the inoculated mice and rats. Thus, it was considered that FNC agar was useful in isolating CK from the oral cavity and cecal contents of mice and rats with subclinical infection of the organism.