Prevalence of theeaeA gene in verotoxigenicEscherichia colistrains from dairy cattle in Southwest Ontario

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Abstract
Summary: This study determined the prevalence of theeaeA gene and its relationship to serotype and type of verotoxin produced in a collection of 432 verotoxigenicEscherichia coli(VTEC) obtained from the faeces of healthy cows and calves in a systematic random survey involving 80 dairy farms in Southwest Ontario. A PCR amplification procedure involving primer pairs which target the conserved central region of the O157:H7eaeA. gene showed that 151 (35·2%) strains were positive for the eaeA gene. All isolates (9–21 for each O group) of O groups 5, 26, 69, 84, 103, 111, 145 and 157 were positive, whereas all isolates (7–34 for each O group) of O groups 113, 132, and 153 and serotype O156:NM (38 isolates) were negative foreaeA. Seventy-three percent of 130 isolates ofeaeA-positive serotypes produced VT1 only compared with 20% of 253 isolates ofeaeA-negative serotypes. We conclude that there is a strong association between certain O groups and theeaeA gene, that serotypes ofeaeA-positive and eaeA-negative VTEC implicated in human and cattle disease are present at high frequency in the faeces of healthy cattle, that VT1 is more frequently associated witheaeA-positive than witheaeA-negative serogroups, and that the eaeA gene is more frequently found in VTEC from calves compared with VTEC from adult cattle.