Listeria risk: authority tells food industry to toughen controls

Detailing some 58 recommendations for risk prevention, the report was prepared by the Food Safety Authority of Ireland's microbiology sub-committee.

Food safety is a leading issue in society today, made ever more urgent by the growth of mass food production. And the incidence of foodborne pathogens can bring heavy costs to industry, employer and government.

The UN-backed World Health Organisation estimates medical costs and the value of lives lost during just five foodborne outbreaks in England and Wales in 1996 were estimated at £300-700 million (€428-€999m); the cost of the estimated 11 500 daily cases of food poisoning in Australia has been calculated at AU$ 2.6 billion (€1.5bn) annually.

The FSAI squarely lays responsibility at the door of the food producer, and consumer.

Dr. John O'Brien, chief executive, FSAI, states:"There is no question that the most effective point of control in managing the spread of L. monocytogenes in food products is at the stage of manufacturing, or during food preparation and storage in the home."​

Ensuring that every food business operates from a clean and sanitised premises should be the first basic step in combating the spread of L. monocytogenes​ in food products.

Regular laboratory testing of food samples and the factory environment should also form a key element of the strategy adopted by the food industry, he adds.

Meanwhile consumers are encouraged to play their part by adhering closely to all manufacturer instructions on ready-to-eat food products.

Food makers are required to test each food batch where the harmful pathogen Listeria monocytogenes​ may be present, such as soft cheese and processed meat products, and in particular those kept refrigerated for a long time where the pathogen can grow at low temperatures.

Although infections caused by listeria are not as common as for salmonella, they can cause anything from diarrhoea to blood poisoning or meningitis, just as the bacterium can lead to miscarriages or cause disease in foetuses and newborns.

Food safety experts estimate that 100 to 1,000 cells can cause the illness. Cooking kills most of the L. monocytogenes​ cells that can grow at refrigeration temperature, but ready-to-eat products, such as fermented sausages, and smoked fish, are not always cooked by consumers before consumption.

Ready-to-eat foods, including frankfurters, pâté, smoked salmon and fermented raw meat sausages, have been identified as a high risk food group as they are intended by the producer or manufacturer for direct human consumption, without the need for cooking or other processing methods usually associated with eliminating or reducing bacteria to levels acceptable for human consumption.

Commonly affected dairy products include soft cheeses, such as brie, camembert and roulade, semi-soft farmhouse cheeses and unpasteurised milk.

Prepared salads, such as coleslaw, are also foods that can support the growth of the pathogen.

Professor Albert Flynn, chairman of the FSAI's scientific committee cites estimates that six to seven cases per year of L. monocytogenes​ infection are reported in Ireland, with one fatality recorded in 2000.

"The infectious dose associated with L. monocytogenes is uncertain, however it is estimated that exposure to less than 1,000 cells may cause serious infection.​

This is very low when compared to salmonella, another foodborne bacterial infection, where an individual must ingest over 100,000 cells of the bacteria to cause infection,"​ comments Prof Flynn.

The average incubation period for a listeria infection is three to four weeks but can also range from one to ten weeks. As such the bacteria can be present in the body for a period of weeks before infection becomes apparent, making it difficult to trace back to a particular food.

In the UK, the Food Standards Agency has set a target of reducing foodborne disease by 20 per cent by 2006, and to further reduce foodborne illness over the next five years (2005-2010).