A bulletin for the Australian Food Industry December 1996
Contents: Enterohaemorrhagic E. coli outbreak in Japan | Cross-contamination and EHEC | Repercussions from food poisoning incidents | Statistical methods and food safety | National food hygiene standard | Botulism linked to cheese
Cross-contamination and EHEC
Foodborne illness caused by EHEC was first recognized in the early 1980's. It is not common but the organism is now regarded as an important pathogen because of the potential seriousness of infection, particularly in children.The O157 serotype is the predominant cause of human infections but other serotypes are involved e.g. the O111 serotype was the agent of the salami food poisoning incident in South Australia in 1995.
Cattle appear to be the main source of infection and most cases to date have been associated with uncooked or undercooked meat. The organism is heat sensitive and normal cooking and pasteurisation processes will destroy it.
However the infective dose may be very low particularly for children, reinforcing the need for hygienic food handling to avoid cross contamination at all points of the food chain.
This has been emphasised by a recent E. coli O157 incident in the USA and Canada in which unpasteurised apple juice has been implicated as the source of infection in about 50 cases. Fruit juices in general have traditionally been regarded as nonhazardous foods due in large measure to their relatively low pH values, typically in the range 3.2 - 4.0. Studies have recently shown that E. coli O157 can survive in fresh pressed, unpasteurised apple juice stored at normal refrigeration temperatures for several days. There is no evidence that the organism can grow at the pH of apple juice but a low infective dose could remain viable during commercial distribution.
It is therefore being postulated that manure which comes in contact with 'drop' apples could be a source of the bacteria in unpasteurised apple juice. However the juice company involved claims to use only tree-picked apples and that all fruit is washed and scrubbed before processing. Cross contamination of juice with small numbers of the bacteria could conceivably have occurred at any point in production. The safety of pasteurised juice has not been questioned.
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