Long-term survival of Escherichia coli O157 on pasture following an outbreak associated with sheep at a scout camp

Aims: To monitor the decay of E. coli O157 in soil (loamy sand) on a scout campsite following an outbreak in humans. Methods and Results: Samples of soil and sheep faeces were collected from the campsite and tested for the presence of E. coli O157 by immunomagnetic separation (IMS) after enrichment in buffered peptone water + vancomycin at 42degreesC for 6 h. Enumeration of target was carried out by direct plating onto sorbitol MacConkey agar plates supplemented with cefixime and tellurite (CTSMAC) incubated at 37degreesC for 24 h. Low numbers (<100 g(-1)) were estimated by the most probable number (3-tube MPN) technique. Conclusions: Survival was observed for 15 weeks. Significance and Impact of the Study: A number of laboratory studies have followed the decay of E. coli O157 in soil, animal faeces and water. This study follows (for the first time) the decay of the organism in soil after an outbreak associated with sheep. It demonstrates the long-term persistence of the organism in the environment and the results will be potentially important in performing risk assessments for both human and animal infection.