Listeria in RTE foods at retail, Costa Rica

Listeria monocytogenes is a pathogenic bacterium associated with RTE meat products sold at the retail level. The objective of this research was to determine the prevalence of Listeria monocytogenes in RTE meat products sold at retail in Costa Rica and to study the factors associated with the levels of contamination; analyzed factors include hygienic practices within stores (cutting techniques, microbial contamination of products) and the behavior of the isolates (persistence against antimicrobials and transfer potential).

A total of 190 samples of RTE meat products were collected and analyzed for the presence of coliforms and Listeria species. Isolates of L. monocytogenes were then evaluated in terms of resistance to disinfectants (quaternary ammonium compounds and chlorine) and their transfer potential from food contact surfaces (knife and cuttingboards). Overall Listeria spp. prevalence was 37,4% (71/190); L. innocua was present in 32,1% (61/190) of the products and L. monocytogenes was found in just 2,6% (5/190) of the samples. Most of the contaminated samples were cut with a knife at the moment of purchase (44,2%). When analyzing practices within the stores, it was observed that L. monocytogenes transfer from inoculated knife to “salchichón” was higher for samples cut right at the beginning of the experiment. Also, L. monocytogenes transfer from inoculated cuttingboards was independent of the number of slices but contamination from plastic was higher than wood. Regarding L. monocytogenes resistance to disinfectants, average reductions of 2,6 ± 1,1 log CFU/mL were detected after 6 minutes of exposure to 200 ppm of chlorine; however, chlorine resistance varied among the strains. Prevalence of L. monocytogenes in RTE meat products sold at retail could be associated with handling practices within the stores; further studies are necessary to estimate the impact of these practices on the overall risk for consumers.

Presence of listeria monocytogenes in ready-to-eat (RTE) meat products sold at retail stores in Costa Rica and analysis of contributing factors, 2021

Journal of Food Protection

Karol Calvo-Arrieta 1Karol Matamoros-Montoya 1María Laura Arias-Echandi 1Alejandra Huete-Soto 1Mauricio Alberto Redondo-Solano 2

doi: 10.4315/JFP-21-020

For risk modelling nerds: Deli meat

Fun observation: Most people think it’s safer to buy deli meat or cold cuts, fresh at the counter, than the pre-packaged stuff, which is probably safer because it contains antimicrobials (in the U.S.) and doesn’t come into contact with all that slicer shit at the deli counter.

Follow up: What’s the difference between a clean and a deep clean? Phallic hyperbole.

Ready-to-eat (RTE) deli meats sliced at retail are predicted to cause 83% of deli meat-associated listeriosis cases annually. While Listeria monocytogenes is commonly found in delis, environmental prevalence varies by store (0–40%).

A deep clean sanitation standard operating procedure (SSOP) executed by a third-party cleaning service immediately reduced L. monocytogenes prevalence in delis, but reductions were not sustained over time. The purpose of this study was to assess the efficacy of a L. monocytogenes predictive risk model and a subsequent deep-clean SSOP (deep clean) conducted by store employees and management complemented with training and facilities improvements all aimed to reduce L. monocytogenes prevalence in stores with known high L. monocytogenes prevalence and evidence of persistence.

Fifty delis among six states were screened using a predictive logistic regression model that estimates the probability of high L. monocytogenes prevalence in a deli. The model identified 13 stores with potentially high L. monocytogenes prevalence; seven stores were confirmed and enrolled for further study. Retail employees executed deep clean; additional interventions (e.g., facilities improvements, training) were incorporated in stores. Environmental samples (n = 20) were collected immediately before and after, and for six months post-deep clean. Deep cleans immediately reduced L. monocytogenes prevalence in six of seven stores tested.

A total of 21/138 (15.2%) samples before and 8/139 (5.8%) samples after deep-cleaning were positive for L. monocytogenes, with a marginal 16.0% decrease on non-food-contact surfaces (NFCS) immediately after deep clean (p = 0.0309, αadj = 0.0125) and a marginal 10.8% on NFCS during follow-up (p = 0.0337, αadj = 0.0125). Employee executed deep cleans with training, education, and maintenance programs can reduce environmental L. monocytogenes prevalence in retail delis, a pivotal part of preventing subsequent cross-contamination to RTE deli meats.

Predictive risk models combined with employee-and management-implemented SSOPs identified and reduced listeria monocytogenes prevalence in retail delis

Food Control

Sophie Tongyu Wua1, Susan R.Hammonsa1m Jingjin Wanga, Clara Assisia, Brittany DiPietrob, Haley F.Olivera

Worry about it: 1 dead, 7 sick from Listeria linked to deli-sliced products: Is steaming hot the same as piping hot?

I do not buy stuff from the deli-counter. I buy stuff that is pre-packaged and may contain antimicrobials, depending on what country you are in.

It’s all about the slicers, whether it’s the little ones at the deli counter or the huge industrial ones in food facilities – I’m looking at you Maple Leaf, source of 23 dead in 2008 in Canada – and how hard they are to properly clean.

Should deli meats be served in hospitals or aged care facilities where the immunocompromised abound?

The U.S. Centers for Disease Control reports a total of 8 people infected with the outbreak strain of Listeria monocytogenes have been reported from 4 states.

All 8 people have been hospitalized, and one death has been reported from Michigan.

Epidemiologic and laboratory evidence indicates that meats and cheeses sliced at deli counters might be contaminated with Listeria monocytogenes and could make people sick.

In interviews, ill people report eating different types and brands of products, including meats and cheeses, purchased from and sliced at deli counters in many different retail locations.

The outbreak strain has been identified in samples taken from meat sliced at a deli and from deli counters in multiple stores.

A single, common supplier of deli products has not been identified.

CDC is not advising that consumers avoid eating products prepared at delis, or that retailers stop selling deli-sliced products.

Retailers should clean and sanitize deli slicers.d

This outbreak is a reminder that people at higher risk for severe Listeria infection should handle deli-sliced meats and cheeses carefully to prevent illness. Pregnant women and their newborns, adults age 65 and older, and people with weakened immune systems are more likely to get sick with listeriosis.

People who are at higher risk for Listeria infection should avoid eating lunch meats, cold cuts, or other deli meats, unless they are heated to an internal temperature of 165°F or until steaming hot just before serving.

If you develop symptoms of a Listeria infection after eating deli-sliced products, contact a healthcare provider and tell them you ate deli-sliced products. This is especially important if you are pregnant, age 65 or older, or have a weakened immune system.

If you have eaten deli-sliced products and do not have any symptoms of a Listeria infection, most experts believe that tests or treatment are not needed, even for people who have a higher chance of Listeria infection.

Listeria bacteria can survive at very low temperatures and can spread easily to other foods and surfaces. Consumers should clean refrigerators, kitchen countertops, utensils, and other surfaces that touch deli-sliced products.

You can take steps to prevent Listeria infection:

Don’t let juice from lunch meat and hot dog packages get on other foods, utensils, and food preparation surfaces.

Wash hands after handling deli meats, lunch meats, deli cheeses, and hot dogs.

Store opened packages of meat sliced at a local deli no longer than 3 to 5 days in the refrigerator.

7 sick from Salmonella at Costco deli in Washington

KOMO News reports a salmonella outbreak has been linked to food prepared in the service deli at the Costco Wholesale Warehouse in Issaquah, and now local health officials are closely monitoring the deli to make sure it is taking steps to prevent further problems.

An investigation by Public Health Seattle & King County found that seven people who got sick between August 2017 and July 2018 all tested positive for the same strain of salmonella, suggesting a common source for the infection.

As the investigation continued, officials discovered in August that all seven people who got sick had shopped at the Costco store in Issaquah. Of those, five bought ready-to-eat food from the service deli and one was an employee at the deli – although there was no evidence that the employee was the source of the outbreak.

It could not be confirmed whether or not the seventh person had purchased food at the Costco deli. One salmonella victim had to be hospitalized, but all seven have since recovered.

The Costco service deli prepares and sells a variety of ready-to-eat foods, but it could not be determined which of those was the source of the outbreak, King County health officials said.

Public health links Salmonella illnesses to Washington Costco deli

The Patch writes that a bunch of Salmonella illnesses have been linked to eating food from a Costco deli in Issaquah, Washington.

The Patch reports that King County health officials released a bulletin today stating,

Since August 28, 2017, we have learned of seven King County residents who tested positive for Salmonella I,4,[5], 12:i:- infections. DNA fingerprinting was performed on the Salmonella bacteria from the seven people who got sick and was identical for all cases, suggesting a common source of infection. Illness onsets occurred sporadically during August 28, 2017–July 13, 2018, and a common epidemiological link among all cases was not established until August 2018; no single food item prepared by the service deli has been identified as the source of the illnesses.

Salmonella is crazy hardy. Sticking around in a deli location for a year, is notable though. Niches in equipment, floors, utensils could be good harborage spots. Someone sent me an outbreak report a while ago about a restaurant that had a really long Salmonella outbreak linked to drains and the environment (I think, I can’t find the post though).

Also notable is that in 2016 another Washington State Costco was also the source of Salmonella I,4,[5], 12:i:- . That incident was linked to four cases and attributed to rotisserie chicken salad.

The deli is not safer: Slicer cleaning and Listeria

The Centers for Disease Control and Prevention (CDC) estimates that 3,000 people die in the United States each year from foodborne illness, and Listeria monocytogenes causes the third highest number of deaths. Risk assessment data indicate that L. monocytogenes contamination of particularly delicatessen meats sliced at retail is a significant contributor to human listeriosis. Mechanical deli slicers are a major source of L. monocytogenes cross-contamination and growth.

In an attempt to prevent pathogen cross-contamination and growth, the U.S. Food and Drug Administration (FDA) created guidance to promote good slicer cleaning and inspection practices. The CDC’s Environmental Health Specialists Network conducted a study to learn more about retail deli practices concerning these prevention strategies. The present article includes data from this study on the frequency with which retail delis met the FDA recommendation that slicers should be inspected each time they are properly cleaned (defined as disassembling, cleaning, and sanitizing the slicer every 4 h).

Data from food worker interviews in 197 randomly selected delis indicate that only 26.9% of workers (n = 53) cleaned and inspected their slicers at this frequency. Chain delis and delis that serve more than 300 customers on their busiest day were more likely to have properly cleaned and inspected slicers. Data also were collected on the frequency with which delis met the FDA Food Code provision that slicers should be undamaged. Data from observations of 685 slicers in 298 delis indicate that only 37.9% of delis (n = 113) had slicers that were undamaged. Chain delis and delis that provide worker training were more likely to have slicers with no damage.

To improve slicer practices, food safety programs and the retail food industry may wish to focus on worker training and to focus interventions on independent and smaller delis, given that these delis were less likely to properly inspect their slicers and to have undamaged slicers.

Retail deli slicer inspection practices: An EHS-Net study, May 2018


Journal of Food Protection, vol. 81 no. 5

EHS-Net reports retail deli slicers cleaning and sanitizing not up to guidance

It’s MMWR day again. The best day of the week.

Retail deli slicers have been identified as a Listeria harborage sites. Courtenay Simmons and colleagues published some work last year that showed food contact surfaces in delis (like slicers) are important spots for cleaning and sanitizing.chefs_choice_meat_slicer_662

CDC’s EHS-Net and others published the results of a 2012 project that shows less than half of surveyed managers and employees reported that slicers were cleaned and sanitized every four hours, as recommended by FDA (and included in the 2013 Model Food Code). Chains faired significantly better than independents in their reported cleaning and sanitizing practices.

Half of managers (49.5%) said that slicers were fully cleaned at least every 4 hours (Table 1). The remaining managers said that slicers were fully cleaned less frequently. Workers reported that 63.0% (393 of 624) of slicers were fully cleaned at least every 4 hours. Deli-level aggregation of these worker-reported data indicated that in 45.8% of delis, all slicers were fully cleaned at least every 4 hours (Table 1). In the remaining delis, at least one slicer was fully cleaned less frequently. Managers and workers agreed on cleaning frequency in 79.0% of delis (215 of 279, r = 0.587, p<0.001).

Multiple regression findings indicate that chain delis reported more frequent slicer cleaning than did independent delis, and delis with more slicers, serving more customers, and selling more chubs daily reported more frequent slicer cleaning than did delis with fewer slicers, serving fewer customers, or selling fewer chubs daily. These characteristics are likely indicators of deli size, and these data are consistent with other findings suggesting that both chain and larger establishments’ food safety practices tend to be better than those of independent and smaller establishments.

People say and do different things; but self reporting is usually optimistic.

60 sick from Salmonella: yes, even co-ops can transmit foodborne disease and bacteria don’t care about your politics

The Boise Co-op says its Salmonella outbreak that has sickened dozens of Treasure Valley residents has been linked to raw turkey, tomatoes and onions in its deli department. organic food store confirmed on its website that the salmonella outbreak started from its deli.

“According to CDHD, the salmonella contamination of the raw produce is a result of possible cross-contamination in our Deli department,” the store wrote on its website.

The latest news comes a day after some customers filed a lawsuit against the store.


Like I tell mommies-to-be: Listeria is prevalent, persistent in retail delis

Purdue University research shows that standard cleaning procedures in retail delis may not eradicate Listeria monocytogenes, which can cause a potentially fatal disease in people with vulnerable immune systems.

amy.pregnant.listeriaA study led by Haley Oliver, assistant professor of food science, found that 6.8 percent of samples taken in 15 delis before daily operation had begun tested positive for L. monocytogenes.

In a second sampling phase, 9.5 percent of samples taken in 30 delis during operation over six months tested positive for the bacteria. In 12 delis, the same subtypes of the bacteria cropped up in several of the monthly samplings, which could mean that L. monocytogenes can persist in growth niches over time.

“This is a public health challenge,” Oliver said. “These data suggest that failure to thoroughly execute cleaning and sanitation protocols is allowing L. monocytogenes to persist in some stores. We can’t in good conscience tell people with weak immune systems that it is safe to eat at the deli.”

In healthy individuals, eating food contaminated with L. monocytogenes may lead to common food poisoning symptoms such as diarrhea or an upset stomach. But the bacteria can cause listeriosis – a serious systemic infection – in immunocompromised people such as the elderly, infants and children, pregnant women and people with HIV. In severe cases, L. monocytogenes can pass through the intestinal membrane and into the bloodstream or cross the blood-brain barrier. The bacteria can also cross the placental barrier in pregnant women, which can trigger abortion.

Ready-to-eat deli meats are the food most associated with L. monocytogenes, which can grow at refrigerator temperatures, unlike Salmonella and E. coli.

Stringent control measures and inspections have tamped down the presence of L. monocytogenes at meat processing plants, but there are no regulations specific to Listeria for retail delis. Recent risk assessments suggest that up to 83 percent of listeriosis cases linked to deli meats are attributable to products contaminated at retail.

oliver-listeria“It’s kind of the Wild West,” Oliver said. “Manufacturing has a zero-tolerance policy for Listeria, but that dissipates at the retail level. The challenge of developing systematic cleaning procedures for a wide variety of delis – which are less restricted environments than processing plants – can make Listeria harder to control.”

Consumers with vulnerable immune systems should buy prepackaged deli meats or heat ready-to-eat meats to 165 degrees, she said. Meat contaminated with L. monocytogenes will not show signs of spoilage, such as sliminess or odor.

The paper was published in the Journal of Food Protection. The abstract is available at

So what should be done about it? Listeria at deli

Postprocessing contamination in processing plants has historically been a significant source of Listeria monocytogenes in ready-to-eat delicatessen meats, and therefore a major cause of human listeriosis cases and outbreaks. Recent risk assessments suggest that a majority of human listeriosis cases linked to consumption of contaminated deli meats may be due to L. monocytogenes contamination that occurs at the retail level. To better understand the ecology and transmission of Listeria spp. in retail listeria4delicatessens, food and nonfood contact surfaces were tested for L. monocytogenes and other Listeria spp. in a longitudinal study conducted in 30 retail delis in three U.S. states. In phase I of the study, seven sponge samples were collected monthly for 3 months in 15 delis (5 delis per state) prior to start of daily operation; in phase II, 28 food contact and nonfood contact sites were sampled in each of 30 delis during daily operation for 6 months. Among the 314 samples collected during phase I, 6.8% were positive forL. monocytogenes. Among 4,503 samples collected during phase II, 9.5% were positive for L. monocytogenes; 9 of 30 delis showed low L. monocytogenes prevalence (<1%) for all surfaces. A total of 245 Listeria spp. isolates, including 184 Listeria innocua, 48 Listeria seeligeri, and 13 Listeria welshimeri were characterized. Pulsed-field gel electrophoresis (PFGE) was used to characterize 446 L. monocytogenes isolates. PFGE showed that for 12 of 30 delis, one or more PFGE types were isolated on at least three separate occasions, providing evidence for persistence of a given L. monocytogenes subtype in the delis. For some delis, PFGE patterns for isolates from nonfood contact surfaces were distinct from patterns for occasional food contact surface isolates, suggesting limited cross-contamination between these sites in some delis. This study provides longitudinal data on L. monocytogenes contamination patterns in retail delis, which should facilitate further development of control strategies in retail delis.

Listeria monocytogenes and Listeria spp. contamination patterns in retail delicatessen establishments in three U.S. states

Simmons, Courtenay; Stasiewicz, Matthew J.; Wright, Emily; Warchocki, Steven; Roof, Sherry; Kause, Janell R.; Bauer, Nathan; Ibrahim, Salam; Wiedmann, Martin; Oliver, Haley F.

Journal of Food Protection®, Number 11, November 2014, pp. 1844-2003, pp. 1929-1939(11); DOI:

Listeria species have been isolated from diverse environments, often at considerable prevalence, and are known to persist in food processing facilities. The presence of Listeria spp. has been suggested to be a marker for Listeria monocytogenes contamination. Therefore, a study was conducted to (i) determine the prevalence and diversity ofListeria spp. in produce production and natural environments and (ii) identify geographical and/or meteorological factors that affect the isolation of Listeria spp. in these environments. These data were also used to evaluate Listeriaspp. as index organisms for L. monocytogenes in produce production environments. Environmental samples collected from produce production (n = 588) and natural (n = 734) environments in New York State were microbiologically analyzed to detect and isolate Listeria spp. The prevalence of Listeria spp. publix.deli.listeria.09was approximately 33 and 34% for samples obtained from natural environments and produce production, respectively. Coisolation of L. monocytogenes and at least one other species of Listeria in a given sample was recorded for 3 and 9% of samples from natural environments and produce production, respectively. Soil moisture and proximity to water and pastures were highly associated with isolation of Listeria spp. in produce production environments, while elevation, study site, and proximity to pastures were highly associated with isolation of Listeria spp. in natural environments, as determined by randomForest models. These data show that Listeria spp. were prevalent in both agricultural and nonagricultural environments and that geographical and meteorological factors associated with isolation of Listeria spp. were considerably different between the two environments. 

Geographical and meteorological factors associated with isolation of Listeria species in New York state produce production and natural environments.

Chapin, Travis K.; Nightingale, Kendra K.; Worobo, Randy W.; Wiedmann, Martin; Strawn, Andlaura K.

Journal of Food Protection®, Number 11, November 2014, pp. 1844-2003, pp. 1919-1928(10); DOI: