Sequence heterogeneity of theeaegene and detection of verotoxin-producingEscherichia coliusing serotype-specific primers

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Abstract
SUMMARY: The distribution of theEscherichia coliattaching and effacing (eae) gene in strains of verotoxin-producingE. coli(VTEC) isolated from cattle and humans was studied. The majority of strains isolated from humans with bloody diarrhoea or HUS and cattle with severe diarrhoea wereeae. positive (82 and 83% respectively). In contrast. 59% of VTEC isolated from asymptomatic cattle wereeaenegative and of the remaining 41 % that wereeaepositive, the majority were serotype O157.H7. The nucleotide sequence of the 3′ end of theeaegene of enteropathogenicE. coli(EPEC) of serotype O55.H7 was found to be almost identical to that of serotype O157. H7. Specific primers are described which detect theeaesequences of VTEC serotypes O157.H7, 0157.H−, and EPEC serotypes O55.H7 and O55.H−. The nucleotide sequence of the 3′ end of theeaegene of serotype O111.H8 differed significantly from that of O157.H7. Primers were developed to specifically identify theeaesequences of VTEC serotypes O111. H−and O111.H8. We conclude that whereas the majority of VTEC associated with disease in cattle and humans possess theeaegene, the gene itself may not be necessary to produce haemorrhagic colitis and HUS. Sequence heterogeneity in the 3′ end ofeaealleles of VTEC permits specific identification of subsets of these organisms.

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