Characterization of freshly isolated Campylobacter coli strains and suitability of selective media for their growth.

Typical and atypical Campylobacter strains were isolated from the colons of cattle and swine by techniques that enabled the selective pressures of antibiotics to be avoided. Some cephalothin-susceptible strains and a strain with an indeterminate hippurate reaction were classified as Campylobacter coli by DNA homology testing. Tetracycline-resistant isolates were obtained from animals with no recorded exposure to antibiotics. A selection of 12 C. coli and 6 C. jejuni strains was used to determine the ability of fresh isolates to grow on a range of selective media. C. coli isolates were inhibited more than C. jejuni on selective media containing antibiotics. The least inhibitory media were Skirrow medium (M. B. Skirrow, Br. Med. J. 2:9-11, 1977) and the charcoal-based media developed by Hutchinson and Bolton (D. N. Hutchinson and F. J. Bolton, J. Clin. Pathol. 37:956-957, 1984) and Karmali et al. (M. A. Karmali, A. E. Simon, M. Roscoe, P. C. Fleming, S. S. Smith, and J. Lane, J. Clin. Microbiol. 23:456-459, 1986). The plasmid contents of the isolates did not appear to be related to their sensitivity to growth on selective (antibiotic-containing) media. The study indicates that selective media used to detect Campylobacter spp. could select against the isolation of C. coli.