Virulence-related DNA sequences and adherence patterns in strains of enteropathogenic Escherichia coli

The presence of the genes for Escherichia coli adherence factor (EAF), atta ching and effacing lesion (eae) and bundle-forming pill (bfp) in 72 strains identified as enteropathogenic E. coli (EPEC) by slide agglutination was e valuated using hybridization and PCR. The adherence property of these strai ns was assayed using 3h HeLa cells adherence assay. The results obtained in dicated that virulence-associated genes were present in 65% of the strains but only ten (13.9%) isolates were positive For all the three markers (typi cal EPEC), 37 (51.4%) isolates carried either one or two of these determina nts (atypical EPEC) and the remaining 25 (34.7%) were negative for all thes e genes. In vitro adherence assay showed that 44 (61.1%) strains adhered to HeLa cells with a defined pattern, 13 (18.1%) isolates adhered loosely wit h no definite pattern and the remaining 15 (20.8%) were non-adherent. Analy sis of the results showed a statistically significant association between t he presence of the virulence-related genes with adherence of the strains wi th a defined pattern (P less than or equal to 0.0001). These results indica ted that since over 60% of the strains identified by serogrouping carried a t least one of the putative virulence markers, it therefore seems that this simple test is still of value in our setting although the need for a confi rmatory test is also indicated. (C) 2000 Published by Elsevier Science B.V. All rights reserved.