Investigation of Virulence-Associated genes and Cytolethal Distending Toxin Production in Campylobacter spp. isolated from broilers

The aim of this study was to investigate the prevalence of virulence and Cytolethal Distending Toxin (CDT) genes in the Campylobacter isolates from intestinal contents and gall bladders of broilers and, to evalute their cytotoxic effects on HeLa cell cultures. These genes play important roles in bacterial adherence to intestinal mucosa, flagella-mediated motility, invasive capability and the ability to produce toxins in Campylobacter pathogenesis. A total of 121 Campylobacter isolates (106 C. jejuni, 11 C. coli, 2 C. lanienae, and 2 C. lari) were used in this study. The frequency of virulence genes in all the isolates were detected in different proportions ranging from 34-93% using Polymerase Chain Reaction (PCR) assay. Cytolethal Distending Toxin A (CDTA), Cytolethal Distending Toxin B (CDTB) and Cytolethal Distending Toxin C (CDTC) genes were found in 66.1%, 65.3% and 66.9% of the Campylobacter isolates tested, respectively (P> 0.05). Of the 19 isolates, only two (one C. jejuni, one C. coli) showed morphological changes such as cell swelling, expansion, growth, and cell shape change in HeLa cell cultures. CDT and virulence genes were detected at low frequencies in C. jejuni, C. coli and C. lari isolates that were obtained from clinically healthy broilers. Although valuable information was attained about the pathogenicity of C. lanienae, additional studies using animal models are necessary for clarification.