ESCHERICHIA-COLI O157-H7 DIARRHEA ASSOCIATED WITH WELL WATER AND INFECTED CATTLE ON AN ONTARIO FARM

A 16-month old female child living on an Ontario dairy farm was taken to hospital suffering from bloody diarrhoea, Escherichia coli O157:H7 was isolated from her stool. Initial tests of well water samples were negative for E. coli by standard methods but culture of selected colif orm colonies on sorbitol-MacConkey agar led to isolation of E. coil O1 57:H7. E. coli O157:H7 was also isolated from 63 % of cattle on the fa rm, The E. coil O157:H7 isolates from the child, the water and the cat tle were phage type 14, produced verotoxins 1 and 2, and were highly r elated on analysis by pulsed held gel electrophoresis. The child did n ot have known direct contact with the cattle and did not consume unpas teurized milk. Hydrogeological investigation revealed the design and l ocation of the well would allow manure-contaminated surface water to f low into the well. This investigation demonstrates that cattle farm we ll water is a potential source of E. coil O157:H7 which may not be ide ntified by standard screening for E. coli in water.