Combating Campylobacter with common sense

Jul 24 2006

A ban on the sale of fresh chicken meat is the not answer to preventing outbreaks of campylobacteriosis says food microbiologist Associate Professor John Brooks.

He says the media focus on the comparatively high incidence of campylobacteria outbreak in New Zealand has been triggered by incomplete information.

"No clear mode of transmission has been established between chicken meat and humans. Campylobacter is also found in cattle and sheep, ducks and domestic pets, and water and dairy farm effluent have also been found frequently to be contaminated."

The call by a University of Otago researcher for a ban on the sale of fresh chicken in favour of frozen will not eliminate the contamination says Dr Brooks.

"Freezing may not provide the hoped-for protection from food-borne illness. The number of bacteria needed for infection to occur differs. For many types of bacteria this is in excess of 100,000 bacterial cells, but for campylobacter the infecting dose may be as low as six cells."

He says there is also confusion about the contamination of chicken carcases in the food processing chain. "Campylobacter cannot grow below about 30 degrees Celsius, which means it can't grow during processing. The bacteria are found in the gut of animals and birds, so spillage of faeces onto the carcase or cross contamination during processing is the most likely route."

Dr Brooks says the Poultry Industry Association and poultry farmers have made strenuous attempts to eradicate campylobacter in chicken flocks - a difficult feat as campylobacter cells are also found in flies.

"Infection spreads through a rearing house like wildfire, and birds are transported to the processing facility in cages, so further cross contamination can occur."

In the kitchen, thawing of frozen chicken can have its own hazards – the release of moisture can cause cross contamination of surfaces and other foods. Dr Brooks says the thorough cooking of chicken will destroy the campylobacter.

"We don't know how many of the reported cases of campylobacteriosis were caused by undercooking of chicken on the barbeque, but we do know that it is difficult to ensure even heating of chicken pieces. This is quite different from barbecuing slices of red meat, which are essentially sterile on the inside and so can be cooked rare with no risk to the consumer."

He says education must be a priority for the control of food poisoning.

"It is common for raw foods to contain pathogens, and the consumer must take some responsibility for controlling food poisoning by preventing cross-contamination in the kitchen and cooking raw foods properly."

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