Molecular typing of enteropathogenic Escherichia coli from diarrheagenic stool samples

Background: Acute diarrhoea is a leading cause of mortality in the developing countries. Enteropathogenic Escherichia coli (EPEC) were originally serogroup-defined E.coli which were associated with infantile diarrhoea. Hence, only serotyping was used for the discrimination of EPEC. Molecular typing methods, due to their higher discriminating ability, may help in the better characterization of the EPEC isolates and these have been used worldwide. However, the molecular typing of the EPEC strains has not been reported from this part of the country. Hence, this study was undertaken with the following aims and objectives. Aim and objectives: This study was aimed at subjecting the EPEC isolates from the stool samples to molecular typing methods like the Random Amplification of Polymorphic DNA (RAPD) and Enterobacterial repetitive intergenic consensus sequences (ERIC) polymerase chain reaction (PCR). The results of these typing methods were compared with those of conventional methods like antibiogram and serotyping to study their similarities and differences. Materials and Methods: E.coli strains (n=35), which were isolated over a period of two years from diarrheagenic stool samples (n=100), were subjected to antibiotic susceptibility testing by the disc diffusion method. The EPEC strains which were confirmed by PCR were serotyped at the National Salmonella and Escherichia Centre, Kasauli, India. The EPEC strains were subjected to molecular typing methods like RAPD and ERIC PCR. Results: Among the 35 E.coli isolates, 25 belonged to the serogroup O101 and they were positive for the eae gene. Among these, one of the eae positive isolates was also positive for the EHEC hlyA gene; five isolates were of the O111 serotype and they had both the eae and the bfp genes; there were five nontypeable strains which were negative for all the virulence genes which were tested. The non typeable E.coli strains were sensitive to all the antibiotics were tested, except ampicillin. Two EPEC isolates which belonging to the serogroup O111, showed genetic similarity in both RAPD and ERIC PCR. Conclusion: EPEC isolates which belonged to same serogroup were found to be highly diverse, as shown by their differing antibiotic susceptibility patterns and by their ERIC PCR and RAPD profiles. The genetic similarities which were observed among few EPEC strains indicated a common ancestral origin or source.