Imposed testing won't guarantee safety of our foods from killer E. coli bacteria

Tuesday 28 June 2011, 4:13PM
By AUT University


Renewed global warnings over food safety have been issued after the outbreak of E. coli spread to France in recent days, hospitalising up to 10 people.

To date, the outbreak of E. coli O104:H4 has spread to 16 countries and killed more than 40 people. And while we aren’t immediately in harms way, Professor of Food Microbiology at AUT University, Dr John Brooks, says New Zealand consumers are not entirely immune from the spread.

“The outbreak of E. coli food poisoning in Germany is one of the worst outbreaks on record and certainly one of the most deadly. Our modern food supply chains are extremely complex. Foods are sourced from all over the world, so finding the source of this outbreak as quickly as possible was imperative,” he says.

At the New Zealand Institute of Food Science and Technology Conference this week, Brooks will discuss the implications for New Zealand food producers of widened testing requirements. The conference takes place in Rotorua from 29 June – 1 July.

“The continuing outbreak of the E. coli O104:H4 infection in Europe - with very high rates of kidney damage and death - is a wake-up call for food producers everywhere. I believe we are seeing evolution in action. A normally benign bacterium has become a killer. That said however, imposing increased mandatory testing will not assure the safety of foods.”

E. coli is a normal inhabitant found in the guts of humans and animals. The strain of E. coli O104:H4 found in the European outbreak is a more virulent strain that has picked up extra genes. This has acquired the ability to produce cell toxins which can penetrate the cells of the gut and result in the potentially fatal Haemolytic Uraemic Syndrome (HUS), causing serious diarrhoea, kidney damage and ultimately death – as in the 44 cases in Germany.

Brooks says the frequency of HUS in this outbreak is much higher than usually observed, with over 3800 cases of infection, resulting in an unprecedented 865+ cases of HUS.

A number of countries have now banned the import of vegetables from the European Union. Last week alone, Russia introduced a ban on meat and milk products from over 300 German companies, following concerns about E. coli.

Tracking down the source of infection through epidemiological investigations may have a success rate as low as 33%, says Brooks. “This shows how difficult it is to pinpoint the source of an outbreak of food poisoning in our highly integrated and widespread food supply chain. At times like this, we often hear calls for increased testing of products before they are released onto the market.

“For a number of reasons, microbiological testing to assure safety of food is just not feasible. Testing is expensive and time consuming. In some cases, the testing period exceeds the shelf life of the product. Ultimately, testing for E. coli O157:H7 would not have picked up the German strain.”

Brooks says the concern for New Zealand meat exporters now is that our trading partners, particularly the US, will demand testing for these pathogenic strains of E. coli.

“Regulators must be strong in the coming months; microbiological testing gives only a retrospective view and imposing increased mandatory testing will not assure the safety of foods.

“The only way we can ensure the safety of our food supply is to introduce controlled lethal steps in processing, such as heating or irradiation, or to put in place rigorous control of every potentially hazardous ingredient, process step, processing facility and distribution chain. This is particularly important with high risk products such as sprouts. “

Professor Brooks is Director of AUT University’s Food Science Research Centre and is Head of Research at the University’s School of Applied Sciences. His areas of research include the study of biofilms in food, aquaculture and medicine. Professor Brooks is also a member of the New Zealand Food Safety Authority’s Scientific Academy.