Study of cytolethal distending toxin (cdt) in Campylobacter coli using a multiplex polymerase chain reaction assay and its distribution among clinical and food strains.

From a collection of 242 food isolates of Campylobacter spp. 72 were identified as Campylobacter jejuni and 170 as Campylobacter coli and of 112 isolates from clinical sources, 92 were identified as C. jejuni and 20 as C. coli. The results for food isolates were in contrast to other reported identifications. Twenty C. coli strains from clinical cases of Campylobacter that occurred in Portugal and 170 isolated from poultry products were examined for the presence of cytolethal distending toxin (cdt) by multiplex polymerase chain reaction assay. CdtA, cdtB, and cdtC were present in 100% of the clinical strains. With respect to the food isolates, the cdtA and cdtC genes were detected in 99.4% of the strains and cdtB in 98.8%. Small point mutations or major deletions within the primer binding sites are possible explanations for these observations but need to be further investigated.