Listeria Found To Persist in Environment For a Year

Despite the efforts of food retailers and food-processing plant managers to maintain a clean, safe environment, strains of Listeria monocytogenes can persist for up to a year or longer, according to Cornell University food scientists in the latest issue of Journal of Food Protection (July 2004).

This suggests that retail stores and food processors can be a continuing source of contamination.The Cornell team examined specific strains of L. monocytogenes that had been found in 125 foods in 50 retail food stores and seven food-processing plants in New York state examined by inspectors of the New York State Department of Agriculture and Markets. The inspectors found the bacteria during routine surveys, sanitary inspections and as a result of consumer complaints between 1997 and 2002.

The bacterium was found directly on food in 47 of 50 retail food stores, including 20 food stores where the bacterium was found on several foods. When the 50 stores were re-inspected weeks, months or even a year later, about 34 percent 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.

The study is intended to help state health departments track the origins of Listeriosis.