*6.2.2 Cytotoxins production*

EIEC strains also carry a plasmid-borne gene, *sen* that mediates a novel 63-kDa enterotoxin (ShET2) [166]. A mutation in this gene was reported to cause a substantial loss in the enterotoxic ability of EIEC strain. Although the role of this gene in the pathogenesis of EIEC is not fully understood, toxins are known to be important in the induction of watery diarrhea during *E. coli* infection. Additionally, plasmid encoding enterotoxigenic and cytotoxigenic factors namely *pic*, *sepA*, *sigA,* and *sat* that belong to SPATEs family and that are reported to contribute to intestinal fluid accumulation in an animal model are carried by EIEC strains. Nonetheless, these genes are not carried by all EIEC strains. Two different studies on the prevalence of the virulence genes among EIEC reported that *sen*, *sigA,* and *pic* were found in at least 70%, 64%, and 27% of the isolates, respectively [167, 168], whereas *sat* gene was found only in 15% of the collection [167].
