Characterization of strains isolated from human stool samples: results from the prospective German prevalence study Arcopath.

Background: constitute emerging food- and waterborne pathogens causing gastroenteritis in humans, but the underlying mechanisms are only incompletely understood. We therefore characterized isolates derived from human stool samples that had been collected during a prospective prevalence study in Germany in vitro. Thirty-six bacterial isolates belonging to the species (n = 24), (n = 10) and (n = 2) were genotyped by ERIC-PCR, the presence of 10 putative virulence genes was assessed and cytotoxic effects on the human intestinal cell line HT-29/B6 were analyzed applying the WST-assay.

Results: Genotyping revealed high genetic diversity within the species , and . Both, and encoded for a large number of putative virulence genes, while fewer genes were detectable in isolates. Notably, the three cytolethal distending toxin (CDT) genes , and were abundant in both isolates. Furthermore, all and , but only one of the isolates exerted cytotoxic effects.

Conclusions: Our study provides evidence for the abundance of putative virulence genes in isolates and prominent cytotoxic effects of and in vitro. The presence of , , in points towards CDT secretion as potential mechanism underlying cytotoxicity as opposed to . However, the association of the virulence factors detected and human morbidity should be addressed in future studies.