Molecular epidemiology of cytolethal distending toxin-producing Escherichia coli

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We have shown that cdtB gene was specifically identified among enteropathogenic E.coli(EPEC). Some of the strains are associated in causing bloody diarrhea among children and exhibited higher production of CDT. The cdtB positive strain mostly belongs to O86a and O127a serogroups. Pulsed-field gel electrophoresis profiles showed that the EPEC strains harboring ctdB were genetically diverse.In this study, 1607 stool specimens were screened for the cdtB harboring enteric pathogens. In the probe hybridization assay, 6 samples (0.4%) were positive and the PCR assay confirmed 5 strains. Form the cdtB probe or PCR positive samples only E.coli strains were isolated and confirmed by serology. Four out of six strains were identified as serogroup O142. Characterization of these strains for different virulence genes specific for diarrheagenic E.coli showed that six strains were enteropathogenic E.coli(EPEC), as they harbored eae as well as bfp genes. We have reported the same trend in our early reports.Expect for two, all the strains harbored cdtA and cdtC genes. These two strains were negative for cdtB by PCR and did not express the CDT in the tissue culture assay. Based on the variation in the sequence of amino acids, the Cdt is classified into CdtI, CdtII and CdtIII. Currently, we are analyzing all our strains to detect the Cdt alleles.Clinical and bacteriological studies have revealed that production of colicin by E.coli having a part of intestinal microbiocenasis is related to the clinical manifestation of inflammatory disease of the gastrointestinal tract. Colicin expression was determined in many enteric pathogens especially among enteropathogenic E.coli(EPEC) and enterohemorrhagic E.coli(EHEC). Colicin expression was confirmed with 3 out of 18 strains (16.7%). There is no correlation between serogroups and colicin expression.