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Food Safety and Inspection
Service United States Department of Agriculture Washington, D.C. 20250-3700 |
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Food Safety and Inspection
Service United States Department of Agriculture Washington, D.C. 20250-3700 |
Backgrounders
February 1999
Contact Information Updated May 2000
Listeria monocytogenes is found in soil and water and can contaminate a variety of raw foods, such as uncooked meats and vegetables, as well as foods that become contaminated after processing, such as soft cheeses and cold cuts. Consumption of food contaminated with Listeria monocytogenes can cause listeriosis, an uncommon but potentially fatal disease.
During the late 1980's, Listeria monocytogenes emerged as a problem in deli meats and other processed products. USDA and FDA worked with plants to improve their procedures and established a "zero" tolerance for the pathogen in ready-to-eat products. Between 1989 and 1993, the rate of illness from Listeria monocytogenes declined 44 percent. Preliminary analysis of rates since 1993 has not shown any changes in rates of illness. However, in the fall of 1998, an increased number of cases of a specific subtype of Listeria monocytogenes led CDC to investigate. As of February 5, the CDC has reported 16 deaths (5 of those are stillbirths or miscarriages), and 73 illnesses in 14 states associated with the current outbreak.
FSIS is concerned about the recent, nationwide outbreak of listeriosis associated with meat and poultry products. The Agency believes this is an appropriate time to reconsider government and industry approaches to addressing Listeria monocytogenes in order to further reduce the risk of human illness.
FSIS is working with the Centers for Disease Control and Prevention (CDC) and State and local health departments to determine the sources of the Listeria monocytogenes. It also is working with State and Federal agencies to review regulatory, enforcement, and educational strategies for reducing illness associated with the pathogen and is holding a public meeting on February 10 to discuss these issues.
In addition, the Food and Drug Administration (FDA), in cooperation with USDA, is undertaking a quantitative risk assessment for Listeria monocytogenes.
Although uncommon, Listeria monocytogenes can cause serious and sometimes fatal infections in pregnant women, newborns, the elderly, and persons with weakened immune systems—such as those with chronic disease, HIV infection, or persons taking chemotherapy for cancer.
The most common manifestation of listeriosis is meningitis, which has symptoms of high fever, severe headache, neck stiffness, and nausea.
Technological advances in testing methodologies are allowing public health agencies to gather more specific information about pathogens isolated from humans and food. Pulsed-Field Gel Electrophoresis (PFGE) technology, now being carried out in public health laboratories around the country, enables molecular subtyping, or fingerprinting, of pathogens isolated from both humans and foods. The ability to subtype pathogens is important because it helps public health agencies to identify a cluster of related illnesses and to link specific products to specific human illnesses when the "fingerprints" match. Since June 1998, a number of cases of listeriosis showing the previously rare "E" pattern through PFGE testing have been reported, and a case control study recently conducted by CDC found that people with this "E" pattern were more likely to have eaten hot dogs.
Bil Mar Foods, a Zeeland, Michigan, processing plant owned by Sara Lee Corporation, voluntarily recalled a number of products on December 22, 1998, based on CDC illness reports implicating its products. Subsequently, CDC and USDA investigators gathered evidence, through PFGE testing, linking Bil Mar Foods with the outbreak. At this point, no other plants have been linked to the current outbreak, but other recalls due to Listeria monocytogenes are underway, and vigilance remains high.
Since 1989, FSIS has had a zero tolerance for Listeria monocytogenes in ready-to-eat products such as hot dogs and luncheon meats and conducts a monitoring program within plants to test for the pathogen. Approximately 3,500 samples are analyzed for Listeria monocytogenes each year. The following product categories are included in the monitoring program: (1) beef jerky, (2) roast beef, cooked beef, and cooked corned beef, (3) sliced ham and luncheon meat, (4) small-diameter sausage, (5) large-diameter sausage, (6) cooked, uncured poultry, (7) salads and spreads, and (8) dry and semi-dry fermented sausage.
In calendar year 1998, out of 3,547 samples of ready-to-eat products analyzed through this monitoring program, 90 samples--or approximately 2.5 percent--tested positive for Listeria monocytogenes. FSIS sampling of just hot dogs from 1993 to 1996 shows that approximately 4.4 percent of samples were positive for Listeria monocytogenes.
In general, product in the plant targeted for Listeria monocytogenes testing is voluntarily put on hold by the plant until results are available. However, in the event that product was distributed to consumers, and a positive sample is discovered, FSIS requests that the plant initiate a voluntary product recall. An inspector also may, at any time, take a sample for analysis, apart from the monitoring program. Follow-up testing is conducted in the plant in response to a positive sample.
FSIS is holding a public meeting on February 10, 1999, to discuss the food safety issues related to Listeria monocytogenes in meat and poultry products. At the meeting, current industry and government procedures will be discussed, including sampling programs for ready-to-eat products and the best ways to reach "at risk" audiences with information. The Agency's goal is to use information gathered from the public meeting to develop a short-term and long-term strategy for research, regulation, education, and enforcement regarding this pathogen.
FDA, in cooperation with USDA, is conducting a quantitative risk assessment for Listeria monocytogenes that will focus primarily on refrigerated, ready-to-eat foods. The risk assessment will: (1) determine consumers’ exposure to the pathogen through the food supply, (2) assess the relationship between the levels of the pathogen ingested and the incidence of illness, (3) determine the foods that pose the greatest risk to consumers and specific subpopulations at increased risk of contracting listeriosis, (4) assess the role that refrigerated shelf life has on the risk of listeriosis from the consumption of high-risk products, and (5) identify research needs and priorities. The risk assessment is scheduled to be completed in the fall of 1999.
For Further Information Contact:
FSIS Congressional and Public Affairs Staff
Phone: (202) 720-3897
Fax: (202) 720-5704