Detection of enteroaggregative Escherichia coli strains from children with diarrhea by use of multiplex PCR and study of their adherence ability to epithelial cells

Enteroaggregative Escherichia coli (EAEC) is an emerging pathogen that cause acute and chronic infantile diarrhea. The stacked – brick appearance of EAEC strains to HeLa or Hep-2 cells is the gold standard assay for the detection of EAEC strains and is different from adherence pattern of EPEC and DAEC. In the present study, a multiplex PCR (mPCR) assay was used for detection of EAEC strains and its results was compared to HeLa cells adherence assay. In this study the E.coli strains isolated from diarrheal children from Tehran children medical center were used. The isolates were identified according to standard procedure. The 170 strains were subjected to mPCR assay. This assay is based on the presence of three plasmid borne genes i.e aaP, aggR, aatA.The mPCR positive and negative strains were further checked for their adherence patterns on HeLa cells. the results of mPCR of these strains revealed that 114 (67%) of these strains were identified as EAEC by this mPCR assay. The frequency of occurance of these genes was 100 %, 96.4 % and 70% for the aaP, aggR,and aatA genes respectively. The 86.9% of mPCR positive strains were HeLa cell adherent (stacked-brick) and only 13.1% of mPCR positive strains were not adherent. On the other hand 27.2% of st rains that on mPCR assay were negative, adhered to HeLa cells in a characteristic manner of EAEC isolates (stacked –brick).the overall results obtained in this study, showed that the mPCR assay used here is able to detect the strains with HeLa cells adherence characteristic of EAEC isolates. Moreover some strains non-adherent on HeLa cells was positive with the mPCR visa-versa. In conclusion it seems this mPCR assay is rapid and specific assay for detection of EAEC strains and especially is suitable for screening large number of isolates in epidemic situation.