Detection of cdtB gene among enteric bacteria in patients with gastroenteritis and irritable bowel syndrome

Introduction: Cytolethal distending toxin (CDT) is one of the bacterial toxins that present in a variety of Gram-negative human pathogens, such as E. coli, Salmonella spp. and Campylobacter spp. CDT consist of three subunits encoded by three adjacent genes, including cdtA, cdtB and cdtC. It is approved thet cdtB had toxic activity and caused DNA damage of the host cell. Despite its presence in different bacterial species, role of CDT in acute and chronic infections, such as gastroenteritis and irritable bowel syndrome (IBS) is unclear. To clear this correlation, we studied the prevalence of cdtB gene among different enteropathogenic bacteria in patients with gastroenteritis and IBS compared with healthy people. Materials and Methods: This study was conducted on stool samples that obtained from patients with gastroenteritis, IBS and healthy people (as control). All the samples were subjected to DNA extraction. cdtB of Campylobacter spp., Yersinia entercolitica, Providencia alkalifacience, Salmonella enterica and E. coli was analyzed by PCR using specific primers. Results: CdtB encoding Campylobacter spp. was found in 7.5% (5/80) and 34.6% (52/150) of patients with IBS and gastroenteritis, respectively. Also, the PCR results showed that 14% (14/150) of the patients with gastroenteritis and 5% (8/80) of IBS patients carried CdtB encoding Salmonellaenterica. None of the samples were infected with CdtB -encoding E. coli and Providensia spp. Finally, all results were confirmed by sequencing. Conclusion: Our results showed the presence of CdtB encoding pathogenic bacteria in IBS patients and those with gastroenteritis. Regarding the high frequency of CdtB encoding Salmonella and Campylobacterspp., it was proposed that infection to these bacterias could be considered as a risk factor for the development of post-infectious IBS in Iranian patients.  Further studies are needed to establish this relationship.