Fate of Escherichia coli O145 present naturally in bovine slurry applied to vegetables before harvest, after washing and simulated wholesale and retail distribution

摘要

Aims: To determine the fate of E. coli on vegetables that were processed through commercial wash treatments and stored under simulated retail conditions at 4oC or wholesale at fluctuating ambient temperatures (0-25oC, dependent on season).udMethods and Results: Bovine slurry that was naturally contaminated with Escherichia coli O145 was applied without dilution or diluted 1/10 using borehole water to growing potatoes, leeks or carrots. Manure was applied one week prior to harvest to simulate a near-harvest contamination event by manure deposition or an application of contaminated water to simulate a flooding event or irrigation from a contaminated water source. At harvest, crops were contaminated at up to two log cfu/g. Washing transferred E. coli into the water of a flotation tank used for potato washing and did not completely remove all traces of contamination from the crop. Manure contaminated potatoes were observed to contain 0.72 cfu E. coli O145/g after processing and retail storage. Manure-contaminated leeks harboured 0.73 – 1.55 cfu E. coli O145/g after washing and storage. There was no cross contamination when leeks were spray-washed. Washing in an abrasive drum resulted in less than perfect decontamination for manure-contaminated carrots. There were five post-distribution isolations from carrots irrigated with contaminated water 24h prior to harvest.udConclusions: Standard commercial washing and distribution conditions may be insufficient to reliably control human pathogenic E. coli on fresh produce.udSignificance and Impact: Previous speculation that the cause of a UK foodborne disease outbreak was soil from imperfectly cleaned vegetables is plausible.