Deadly food pathogen can live for a year
to maintain a clean, safe environment to beat food pathogens, but
food scientists from the US report that strains of the deadly
pathogen Listeria monocytogenes can persist for up to a year
or longer.
Scientists led by Brian Sauders and Martin Wiedmann at Cornell University studied specific strains of L. monocytogenes identified in 125 foods in 50 retail food stores and seven food-processing plants in New York state.
Inspectors had found the bacteria during routine surveys, sanitary inspections and as a result of consumer complaints between 1997 and 2002.
"When the 50 stores were re-inspected weeks, months or even a year later, about 34 per cent had persistence of the same strains of Listeria. Of the seven food-processing plants where Listeria was found, three had persistent strains of the bacterium," report the scientists in the July 2004 issue of the Journal of Food Protection.
Foodborne illness caused by microorganisms is a large and growing public health problem. Listeria can cause listeriosis, a deadly disease that primarily affects pregnant women, newborn children, and adults with weakened immune systems. Each year in the US alone about 2,500 people are infected, of which one-fifth die. Pasteurisation and cooking kill the bacterium.
Listeria used in Cornell study was detected in ready-to-eat delicatessen foods like ham, chicken, roast beef and smoked fish. It was also found in hummus, imitation crab, cheeses and in foods requiring cooking before consumption, such as hot dogs and raw foods including beef, turkey, lobster tails and shrimp.
According to the UN-backed World Health Organisation (WHO) changes in farm practices, more extensive food distribution systems and the increasing preference for meat and poultry in developing countries all have the potential to increase the incidence of foodborne illness.
And the incidence can also be quite an expense for society. WHO estimates that the medical costs and the value of the lives lost during just five foodborne outbreaks in England and Wales in 1996 were estimated at £ 300-700 million and the cost of the estimated 11 500 daily cases of food poisoning in Australia has been calculated at AU$ 2.6 billion annually.
According to the Cornell study food scientist Wiedmann, food retailers have a harder time controlling Listeria than food processors. While food processors can control people entering the plant, retailers cannot always control the pathogens introduced by customers and employees.
"Listeria is a very hardy organism. Even if you think you're doing a good job of cleaning and getting rid of Listeria, it is likely to return. Normal cleaning and even super cleaning does not always get rid of it. It's a tribute to Listeria's ability to survive," said the researcher, adding that considerable gaps still exist in our understanding of the transmission of human listeriosis.
