SEQUENCE HETEROGENEITY OF THE EAE GENE AND DETECTION OF VEROTOXIN-PRODUCING ESCHERICHIA-COLI USING SEROTYPE-SPECIFIC PRIMERS

The distribution of the Escherichia. coli attaching and effacing (eae) gene in strains of verotoxin-producing E. coli (VTEC) isolated from c attle and humans was studied. The majority of strains isolated from hu mans with bloody diarrhoea or HUS and cattle with severe diarrhoea wer e eae positive (82 and 83% respectively). In contrast, 59% of VTEC iso lated from asymptomatic cattle were eae negative and of the remaining 41% that were eae positive, the majority were serotype O157.H7. The nu cleotide sequence of the 3' end of the eae gene of enteropathogenic E. coli (EPEC) of serotype O55.H7 was found to be almost identical to th at of serotype O157.H7. Specific primers are described which detect th e eae sequences of VTEC serotypes O157.H7, O157.H-, and EPEC serotypes O55.H7 and O55.H-. The nucleotide sequence of the 3' end of the eae g ene of serotype O111.H8 differed significantly from that of O157.H7. P rimers were developed to specifically identify the ene sequences of VT EC serotypes O111.H- and O111.H8. We conclude that whereas the majorit y of VTEC associated with disease in cattle and humans possess the eae gene, the gene itself may not be necessary to produce haemorrhagic co litis and HUS. Sequence heterogeneity in the S' end of eae alleles of VTEC permits specific identification of subsets of these organisms.