Detection of cytolethal distending toxin activity and cdt genes in Campylobacter spp. isolated from chicken carcasses

This study was designed to determine whether isolates from chicken carcasse s, the primary source of Campylobacter jejuni and Campylobacter coli in hum an infections, commonly carry the cdt genes and also whether active cytolet hal distending toxin (CDT) is produced by these isolates. Campylobacter spp . were isolated from all 91 fresh chicken carcasses purchased from local su permarkets. Campylobacter spp. were identified on the basis of both biochem ical and PCR tests. Of the 105 isolates, 70 (67%) were identified as C. jej uni, and 35 (33%) were identified as C. coli, PCR tests amplified portions of the cdt genes from all 105 isolates. Restriction analysis of PCR product s indicated that there appeared to be species-specific differences between the C. jejuni and C, coli cdt genes, but that the restriction patterns of t he cdt genes within strains of the same species were almost invariant. Quan titation of active CDT levels produced by the isolates indicated that all C . jejuni strains except four (94%) had mean CDT titers greater than 100. On ly one C. jejuni strain appeared to produce no active CDT. C. coli isolates produced little or no toxin. These results confirm the high rate of Campyl obacter sp, contamination of fresh chicken carcasses and indicate that cdt genes may be universally present in C. jejuni and C. coli isolates from chi cken carcasses.