*3.4. Distribution of cdtA, cdtB, and cdtC*

*Campylobacter* can produce CDT, composed of A, B, and C subunits, which are encoded by *cdtA*, *cdtB*, and *cdtC* genes [44]. The 71.1% of the *Campylobacter* isolates had these three genes (Table 5). Nine of 15 chicken *Campylobacter* isolates and 23 of 30 duck *Campylobacter* isolates had the three *cdt* genes. Four isolates were found to be without any *cdt* genes and nine isolates had two *cdt* genes (*cdtA+*/*cdtB+*, *cdtA+*/*cdtC+*, or *cdtB+*/*cdtC+*). There was no relationship between the distribution of *cdt* genes and the regions the isolates had been obtained from. Oh et al. [45] showed that 37 *C. jejuni* isolates out of 38 chicken samples had all *cdt* genes. Findik et al. [5] found that 75.6% of *C. jejuni* isolates (127 isolates out of 168) from various sources, including human, poultry, cattle, sheep, and dog, had all *cdt* genes and five isolates were without *cdt* genes. In Brazil, all *cdt* genes were detected in 66.7% of *Campylobacter* isolates [46]. These results indicate that most *Campylobacter* isolates from our study have the potential to produce CDT.


**Table 5.** Cytolethal Distending Toxin (CDT) gene profiles of *Campylobacter* isolated from chicken and duck carcasses at wet markets.
