The potentially deadly Listeria bacteria was found in 32.2% of the uncooked turkey parts randomly selected from supermarket shelves and analyzed for the contaminant by University of California, Davis researchers, according to a recent report.
"The study demonstrated the high prevalence of Listeria and specifically Listeria monocytogenes in (raw) turkey products," the article, in the Journal of Food Protection, stated. "Turkey meat is . . . a major food source of L. monocytogenes. "
In 1985, L. monocytogenes was identified as the pathogen present in the Mexican-style soft cheese, sold under the brand name Jalisco, that caused more than 142 illnesses in Los Angeles County. The outbreak resulted in 47 deaths, mostly stillborn infants.
The UC Davis study is the first to explore the presence of this particular organism in raw turkey meat, according to the journal report.
Poultry industry officials said that the UC Davis figures were inflated, if not outright wrong.
"That sounds phenomenally high to me. I'd be surprised if that figure was true," said Stuart Proctor, executive vice president of the National Turkey Federation in Reston, Va. Proctor insisted, in any event, that cooking turkey to well doneness, or 185 degrees Fahrenheit, would kill any Listeria present and eliminate the health threat.
Even so, a top U.S. Department of Agriculture official called the UC Davis report a high-quality effort and said the lead researcher, Constantin A. Genigeorgis, is among the best in his field.
Genigeorgis and his colleagues conducted the study in the Department of Epidemiology at the UC Davis School of Veterinary Medicine.
Their findings follow disclosure, earlier this year, of a federal study that indicated Salmonella contamination of chicken may be as high as 60%. The UC Davis study seems findings seem to lend further support to consumer groups' claims that sanitation is declining in the nation's poultry processing plants.
"It is a fact of life: we have harmful pathogens in raw poultry," Genigeorgis said. "A Listeria- positive rate of 32.2% is pretty high. . . . It's significant."
Marketing raw turkey or other uncooked meats containing Listeria is not illegal because it is assumed that any bacteria present will be destroyed in the cooking process. However, the federal government has established a zero-tolerance for Listeria in any cooked or ready-to-eat meats such as deli items.
Lester Crawford, administrator of the USDA's Food Safety and Inspection Service, said that Listeria is ubiquitous, or found throughout the environment. The bacteria is even present at similar levels in some types of fresh produce, he said.
Crawford acknowledged that this particular pathogen necessitates extra caution on the part of manufacturers, retailers and consumers.
" Listeria is one of the most troubling organisms to deal with in the food safety realm because it can (survive and breed) in refrigeration," he said.
The UC Davis study's initial phase involved testing 225 samples of turkey gathered during three different trips to a slaughterhouse. Twelve, or 5.3%, tested positive for Listeria. Following the slaughterhouse visits, researchers collected 180 turkey part samples--wings, drumsticks and tails--from three supermarkets in the Davis area. Of these, 58 or 32.2% showed signs of Listeria. (Sample collection locations were not named.)
The disparity between the low contamination rates found at the plant and the higher retail levels is an area that needs further study, the researchers stated. However, while conducting the slaughterhouse sampling program Genigeorgis also ran Listeria tests on meat handlers' hands and gloves. He found 30% positive for Listeria. Thus, employee handling was implicated as a likely source of contamination.
"The current technology for slaughtering birds is not sufficient," said Genigeorgis. "People are handling so many carcasses (in these plants) that if just one person's hands get contaminated then it can cause 300, or more, birds to be infected throughout the day."
The USDA's Crawford said that the discovery of Listeria on workers' gloves was troubling.
"It means that the organism is colonizing the (entire) plant. . . . It grows on cold floors and in wet climates. Plant sanitation efforts need to be especially careful," Crawford said.
An estimated 1,700 people become infected with Listeriosis annually in the United States. However, the actual number of illnesses is vastly under-reported as is the case with virtually every food-borne illness, according to health officials. Even though the number of diagnosed infections is small, Listeriosis has a high fatality rate of between 35% and 40%, according to various estimates.