DIFFERENTIATION IN VIRULENCE PATTERNS OF ESCHERICHIA-COLI POSSESSING EAE GENES

In this study 98 Escherichia coil strains which belonged to traditiona l enteropathogenic (EPEC) serotypes and 82 enterohemorrhagic E. coil ( EHEC) strains were screened by polymerase chain reaction (PCR) for the presence of E. coil -attaching and -effacing (eae) genes. These strai ns were also hybridized with the enteropathogenic adherence factor (EA F) probe and examined in the fluorescence actin staining (FAS) test. T he results obtained from the individual strains demonstrated that all 26 class I EPEC with localized adherence to HEp-2 cells carried EAF an d eae genes. In contrast, of 72 EPEC strains with no or diffuse adhere nce only 1 strain was EAF positive and 6 strains had eae. Of 82 EHEC s trains a total of 75 carried eae sequences. Of considerable interest, 15 of 21 E. coil strains that lost their sit genes during subcultivati on were found to be eae positive. As controls a total of 53 enterotoxi genic and enteroinvasive E. coli, and 125 E. coli strains from the nor mal flora were investigated and all displayed negative results in the eae-PCR. From the 201 strains comprising classical EPEC serotypes, EHE C and E. coil with lost sit genes, a total of 126 displayed a positive FAS test and 122 reacted in the eae-PCR. Only 4 strains were FAS test positive but eae-PCR negative. Our data indicate that E. coli strains possessing the eae genes are heterogenous with respect to their virul ence determinants. Loss of virulence plasmids and phage-encoded sit ge nes either in the host or during storage may contribute to this hetero geneity. The eae-PCR detected all class I EPEC and 91.5% of the EHEC. For diagnostic purposes we, therefore, recommend the combination of ea e- and sit-specific gene probes which allowed a 100% detection of the class I EPEC and EHEC strains investigated here.