WGS gives investigators detailed information about the bacteria causing illness. In this investigation, WGS showed that bacteria isolated from ill people were closely related genetically.
This means that people in this outbreak were more likely to share a common source of infection. As of January 26, , a total of 12 people infected with the outbreak strain of Listeria monocytogenes were reported from four states. A list of the states and the number of cases in each can be found on the Map of Reported Cases page. Listeria samples from ill people were collected from August 6, , to October 30, All 12 people were hospitalized, and one death was reported from Florida.
Epidemiologic evidence showed that deli meat was the likely source of this outbreak. State and local public health officials interviewed ill people about the foods they ate in the month before they became ill.
Of the 11 people interviewed, all reported eating Italian-style deli meats, such as salami, mortadella, and prosciutto. They reported purchasing prepackaged deli meats and meats sliced at deli counters at various locations. USDA-FSIS and state officials reviewed records collected from stores where ill people purchased deli meats to find a common supplier of deli meats. They also tested deli meat products that ill people reported eating. However, they did not find a common supplier or a specific type of deli meat as the source of this outbreak.
Since L. Other conditions that may increase susceptibility to listeriosis are diabetes, cirrhosis, asthma, and ulcerative colitis. Healthy people are generally at a low risk of contracting L. Some research suggests that use of antacids also may increase the risk of contracting listeriosis.
Although listeriosis is relatively uncommon, it is a potentially fatal disease and frequently results in spontaneous abortions in pregnant women.
Even though the symptoms may be relatively mild in the mother, the illness may be transferred to the fetus, causing serious illness or fetal death.
Symptoms of L. The onset of the disease can occur anywhere from a few days up to 6 weeks after ingestion of L. Listeriosis is clinically defined when the bacterium is isolated from blood, cerebrospinal fluid, or an otherwise normally sterile site such as the placenta. The latest figures from the Centers for Disease Control indicate that there may be as many as 2, cases of L. The infectious dose has not been established at this time, but it is estimated that consuming as few as 1, organisms may be enough to cause illness in susceptible people.
Because L. Due to foodborne illness associated with L. As a result, a large number of recalls have occurred since Today, a major food safety concern is that of recontamination of RTE or precooked foods after thermal processing. Examples of foods in which post-processing contamination has occurred and caused major listeriosis outbreaks include hot dogs and luncheon meats.
In , one of the largest outbreaks of L. Effective control of L. Even though the risk of contracting listeriosis is relatively low, the consequences are devastating for both the consumer and the processor when it does occur. The presence of L. Employee training is another step in controlling the problem.
Employees must understand the organism, observe basic sanitation principles, and gain the same sense of personal responsibility exhibited by management and regulatory officials. The U. FSIS has provided guidance to the industry on practices that have been successful in meat and poultry operations to prevent the spread of L.
Testing for L. Plants must focus on preventing contamination of cooked products by L. However, L. The primary sources of L. These biofilms provide nutrients and a place of attachment for growing bacteria, including L. Products that have been fully cooked and will be consumed as packaged, without further heat treatment, present the highest risk to consumers if contaminated with L.
In order to control L. A pre-processing checklist has been developed to help processors evaluate areas of high risk see appendix. Figure 2. If used for raw products and not cleaned and sanitized properly, tables may be a source of L.
In addition to contamination at food-contact areas, many opportunities exist for contamination from the environment. For instance, spray from hoses may splash or atomize and carry L.
Figure 3. Due to the moisture content and difficulty during cleaning, drains are a potential reservoir of L. Figure 4. Standing water may be a potential reservoir of L. Figure 5. Figure 6. To prevent cross-contamination from raw to ready-to-eat areas, it is important to use cleaning tools, such as brushes, for one job only and to replace them periodically.
Knowing the location of potential sources of contamination is very important in producing a safe RTE product, as most outbreaks and recalls are due to post-processing contamination. In general, once proper cooking has occurred, manufacturing a safe product depends on proper sanitation, limited handling, and elimination of cross-contamination in the RTE processing areas.
Figure 7. Once they have found a surface to attach, L. Figure 8. Maintenance tools used in raw areas may be a source of cross-contamination in ready-to-eat areas if they are not properly cleaned and sanitized prior to use.
Figure 9. Hollow table legs in RTE areas may trap food and water, creating a harborage site for L. Figure Rusty and pitted surfaces, such as this drain cover, may be a source of L.
Since they come in direct contact with floors and drains, cracked hoses may be a source of L. Wheels should be covered to prevent splash from the floor or drains. Wheels also should be easily cleaned to prevent cross-contamination of L. Light switches may be another source of contamination of L.
Processors of RTE products should ask three questions when determining the risk of exposure of their products to Listeria monocytogenes :. In order to be guaranteed incapable of supporting the growth of L. It is important to verify that all thermal processes and procedures meet the requirements for pathogen destruction.
There are many considerations for controlling L. Some of these include:. One-third of raw, commercially available ground chicken and turkey and about 10 percent of broiler carcasses, cow and bull carcasses, and raw ground beef harbor L. Also, percent of turkey carcasses, hog carcasses, and steer and heifer carcasses have been found to harbor L. Given these high levels of contamination in raw products, having processes that will eliminate the organism is important.
SSOPs should be established to provide effective and consistent results. Effective equipment sanitation includes the following steps:. Processors can establish the effectiveness of plant sanitation and learn the location of potential sources of contamination by conducting baseline microbial testing of both environmental and contact surfaces.
These can all be used to gain information about cleaning and sanitation procedures. ATP bioluminescence systems are real-time tools that can be used to assess information about sanitation procedures. Frequency of sanitation will be determined, to some extent, by the type of products and the risk involved see Table 2.
Equipment and tools that are only used to process RTE products should be sanitized before and after use. Wash your hands Wash your hands after handling raw meats. Always wash hands after contact with farm animals, pets, animal feces, and animal environments. Wash hands after using the bathroom and changing diapers, and before handling or eating any food.
Hand Hygiene More information about washing your hands. Keep your food preparation areas clean Never place cooked meat or poultry on the unwashed plate that held the raw product. Wash raw fruits and vegetables before eating.
Keep raw meat and poultry separate from produce and other foods when shopping for and storing groceries. Wash hands, cutting boards, countertops, cutlery, and utensils after touching raw poultry or meat. FSIS results of ready-to-eat products analyzed for Listeria monocytogenes — summary by all projects.
In recent years, FSIS and industry stepped up their sampling programs for Listeria in processing environments and on ready-to-eat meat and poultry products. FSIS has established regulations that require manufacturers to have environmental sampling and testing programs and have further established risk-based processing alternatives to further eliminate or prevent growth of inadvertent Listeria contamination.
The goal of the effort is to monitor the adequacy of the food safety process management system to produce product that does not contain L. The decline in the incidence of L. The prevalence of L. Cooking product to F for a few seconds is sufficient to kill these bacteria. Consumers with questions should visit www.
Michael Doyle, Ph. Martin Wiedmann, Ph. Listeria monocytogenes Listeria is a bacterium that is commonly found in the environment, on our hands and in our refrigerators.
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