What’s in your weed?

In Hawaii, one of the testing labs certified by the state to check the quality of medical marijuana said they found contamination in more than half of the samples from the black market.   

The lab, Steep Hill Hawaii, says over 50 percent of the black market product had contaminants that included mold, yeast, and pesticides. 

The lab says that doesn’t mean all homegrown products are bad, but patients should be aware of what’s in their medicine. 

“I personally was shocked to find out how much stuff was in black market cannabis that you would never expect. E. coli, which comes from fecal matter. Salmonella, which comes from raw egg and chicken. We found that on product we tested,” said Michael Covington, of Steep Hill Hawaii. 

In Canada, CannaDrinks may be all the rage in some parts of the world, but there are some serious health concerns surrounding new products being formulated.

Sure it sounds cool, to order some cannabis-infused drinks at the bar for you and your buddies. However, a leading food safety expert is warning that these cool drinks may be dangerous, and the public (apparently) needs to take note.

While a $245 million deal was penned between Constellation Brands and Canopy Growth last week, for a 10 percent stake of CP, Canada’s largest cannabis producer, to produce the new CannaDrinks, Rick Holley claims the drinks are problematic, “[Producers] could screw this all up if they don’t get into the mechanics of how to safely prepare and develop new food products,” he said, adding, “They could kill people!”

BNN reported that Constellation Brands told them via email that the company, “has a long-standing commitment to producing products with the highest quality standards and that comply with all regulations.”

According to Lawrence Goodridge, a McGill University food safety expert (Larry, you’re an expert), alcohol has the advantage of killing bacteria and toxins in sealed bottles or cans, whereas cannabis-infused products may not, “Because cannabis is a plant, there are certain concerns — like the possibility of pesticides used in production, or the type of fertilizer used, or the potential presence of heavy metals that could be toxic to humans,” said Goodridge, adding that, “Bacteria like e-coli or listeria that could be on the plant and that could make it onto the food, whether it is drinks or edibles, the risk is the same — but alcohol is special because we know that helps to kill some of those toxins.”

Also, Sikora et al. identified a case of Hepatitis A associated with cannabis use.

We identified a case of acute Hepatitis A virus (HAV) infection linked to cannabis use. The local Public Health department received report of a man in his mid-20s with a classic presentation of hepatitis – jaundice, abdominal pain, vomiting, general malaise, and dark urine – as well as elevated serum aminotransferase levels and a positive anti-HAV IgM. Upon questioning, he reported no contact with ill individuals, or travel outside his metropolitan area. His exclusive source of water was the local municipal supply. He reported consuming mainly pre-packaged lower risk foods from large chain-style supermarket stores and eating at several local restaurants. While administering the questionnaire, the investigator identified that the patient smoked cannabis. Upon request, the patient agreed to provide a sample of cannabis for testing purposes. A viral elution of fresh cannabis leaves was completed. The sequences derived from the patient’s serum sample and the eluate from the cannabis leaves were identical, but did not match any other HAV sub-genotype 1B sequences from Canadian isolates within the National Microbiology Laboratory database. Hepatitis A virus can survive >60 days when dried and kept at room temperature and low humidity; HAV can remain infectious in water at room temperature for 300 days. It cannot be concluded with certainty that the cannabis was the source of the hepatitis A; however, as other sources were excluded, or were of lesser probability, the association of cannabis with his disease acquisition remains strong.

 

Listeria triggers major recall of veggies across US and Canada

A leading vegetable supplier in California, Mann Packing, voluntarily recalled products that might have been contaminated with Listeria.

The recall affects packaged produce at multiple supermarkets across the United States and Canada including Walmart, Whole Foods, Trader Joe’s, Meijer, Albertson’s and Safeway.

Mann Packing is issuing this recall out of an abundance of caution,” the company said in a statement, adding that it is cooperating with U.S. and Canadian health officials to recall the products.

No illnesses have been linked to the products, the company said. The contamination risk was picked up by the Canadian Food Inspection Agency through random sampling.

The affected items were listed as “best if used by” October 11 to October 20.

About 1,600 people become infected with listeria each year, and about 260 die, according to the U.S. Centers for Disease Control and Prevention.

Maybe not so slightly pink: Properly cooked pork chops may contain threat of Listeria and Salmonella for consumers

If you are eating leftover pork chops that have not been cooked well-done, you’re putting yourself at risk for Salmonella and Listeria exposure. While many individuals prefer to consume their pork medium, a new study published in Risk Analysis: An International Journal revealed that cooking pork chops to an acceptable temperature does not completely eliminate pathogens, providing these cells with the opportunity to multiply during storage and harm consumers.  

The study, “Impact of cooking procedures and storage practices at home on consumer exposure to Listeria monocytogenes and Salmonella due to the consumption of pork meat,” found that only pork loin chops cooked well-done in a static oven (the researchers also tested cooking on a gas stove top) completely eliminated the Listeria and Salmonella pathogens. Other levels of cooking, i.e. rare and medium, while satisfying the requirements of the product temperature being greater than or equal to 73.6 degrees Celsius and decreasing the pathogen levels, did leave behind a few surviving cells which were then given the opportunity to multiply during food storage before being consumed.  

It is generally believed that when meat is heat treated to 70 degrees Celsius for two minutes, a one million cell reduction of E. coli, Salmonella, and Listeria is achieved and thus the meat is free of pathogens and safe to eat. However, a report by the European Food Safety Authority revealed that more than 57 percent of Salmonella outbreaks in 2014 were in the household/kitchen, and 13 percent were associated with inadequate heat treatment. 

“The results of this study can be combined with dose response models and included in guidelines for consumers on practices to be followed to manage cooking of pork meat at home,” says Alessandra De Cesare, PhD, lead author and professor at the University of Bologna.  

In order to assess the pathogen levels in cooked pork, the researchers, from the University of Bologna, the Institute of Food Engineering for Development and the Istituto Zooprofilattico delle Venezie, tested 160 packs of loin chop. The samples were experimentally contaminated with 10 million cells of L. monocytogenes and Salmonella to assess the reduction in pathogens after cooking, in accordance with the Food Safety and Inspection Service (FSIS) and British Retail Consortium (BRC) specifications (ensuring a reduction of at least 100,000 and 1,000,000 cells, respectively). The samples were contaminated on the surface, to mimic contamination via slaughter and cutting.  

The samples were divided into groups to be cooked either on gas with a non-stick pan or in a static oven. In each setting, the pork chops were cooked to rare, medium, and well-done. For each cooking combination, 40 repetitions were performed for a total of 240 cooking tests.  

The researchers also interviewed 40 individuals between the ages of 20 and 60 to determine household consumer habits regarding doneness preferences. Prior published research was referenced to define meat storage practices and the probability that consumers store their leftovers at room temperature, in the refrigerator or discard them immediately. Growth rate data for the pathogens at each temperature were obtained using the software tool ComBase.  

The only cooking treatment able to completely inactivate the pathogens was oven well-done, which achieved a reduction between one and 10 million cells. Statistical analyses of the data showed significant differences related to level of cooking and cooking procedure. However, the researchers explained that factors such as moisture, water activity, fat levels, salts, carbohydrates, pH, and proteins can impact the cooking treatment and effectiveness and, as a consequence, on bacteria survival. These results emphasize the needs to consider the form of pork (such as whole muscle versus ground) being cooked, in addition to the final temperature necessary to inactivate pathogens.  

The results show that a reduction between one and 10 million of pathogen cells was reached when applying all of the tested cooking treatments, with product temperatures always reaching 73.6 degrees Celsius or greater. However, according to the simulation results using the obtained cell growth rates, the few surviving cells can multiply during storage in both the refrigerator and at room temperature, reaching concentrations dangerous for both vulnerable and regular consumers.  

After storing leftovers, there was a probability for the concentration of pathogens to reach 10 cells ranging between 0.031 and 0.059 for all combinations except oven well-done. Overall, the mean level of exposure to Listeria and Salmonella at the time of consumption was one cell for each gram of meat. The results obtained from this study can be implemented in guidelines for consumers on practices to follow in order to manage cooking pork meat at home.  

 

Deep clean is more than adjectives: it means deep clean

We investigated 543 Listeria monocytogenes isolates from food having a temporal and spatial distribution compatible with that of the invasive listeriosis outbreak occurring 2012–2016 in southern Germany. Using forensic microbiology, we identified several products from 1 manufacturer contaminated with the outbreak genotype. Continuous molecular surveillance of food isolates could prevent such outbreaks.

Molecular tracing to find source of protracted invasive listeriosis outbreak, Southern Germany, 2012-2016

Emerging Infectious Disease, vol 23, no 10, October 2017, Sylvia Kleta, Jens Andre Hammerl, Ralf Dieckmann, Burkhard Malorny, Maria Borowiak, Sven Halbedel, Rita Prager, Eva Trost, Antje Flieger, Hendrik Wilking, Sabine Vygen-Bonnet, Ulrich Busch, Ute Messelhäußer, Sabine Horlacher, Katharina Schönberger, Dorothee Lohr, Elisabeth Aichinger, Petra Luber, Andreas Hensel, and Sascha Al Dahouk

https://wwwnc.cdc.gov/eid/article/23/10/16-1623_article

Raw milk is risky

I have friends who grew up on the farm their entire lives and insist on drinking raw milk as they feel that pasteurization completing devoid the milk of nutrients. I can preach about the dangers of consuming raw milk supported with scientific facts but that’s not going to change their minds. They’re adults, they can make their own choices; just don’t impose your choice on a child. When I was younger I was courting a girl who lived on a dairy farm in rural Manitoba (Canada). She insisted on drinking raw milk and offered some to me. I was aware that raw milk was risky but this way before my food safety days. So like many boys courting women, you sometimes make foolish mistakes and so I drank the milk. Puked it up. Not because of microbial reasons, just tasted horrible, maybe it was that batch, not sure.

Kristi Rosa reports
The Centers for Disease Control and Prevention (CDC) have issued an official health advisory regarding a rifampin/penicillin-resistant strain of RB51 Brucella that has been linked with the consumption of raw milk; this follows a alert issued by the Texas Department of State Health Services (DSHS) that was issued back in mid-August.

The DSHS defines raw milk as “milk from cows or other animals that has not been pasteurized to kill harmful bacteria.” Raw milk can be contaminated with several different bacteria, including Listeria, Salmonella, Escherichia coli, and Campylobacter—all bacteria that are known to be responsible for countless disease outbreaks.

The individual who contracted brucellosis is a Texas resident who was exhibiting fever, muscle and joint pain, as well as fatigue. The DSHS reports that blood culture revealed the bacteria responsible for these symptoms was, in fact, Brucella. Further investigation tracked the infection back to a potential source: a licensed raw milk dairy based in Paradise, Texas, called K-Bar Dairy.

The CDC stresses that any individuals who have consumed raw milk from this dairy between June 1, 2017 and August 7, 2017 should “receive appropriate post-exposure prophylaxis (PEP).” These individuals are thus at increased risk for infection and should contact their healthcare providers to inquire about PEP and undergo potential diagnostic testing.

K-Bar Dairy has fully cooperated with the CDC’s investigation and has contacted customers and advised them to dispose of any milk that may be contaminated. However, the dairy does not have a record of all customers, therefore, the DSHS alerted the public about the recall on August 14, 2017.

The rest of the story can be found here.

Denmark: 1 dead, 4 sick from Listeria in salmon

Joe Whitworth of Food Quality News reports that four people have been sickened and one has died from Listeria in salmon processed in Poland and sold in Denmark.

Dansk Supermarked Group issued a recall after Fødevarestyrelsen (Danish Veterinary and Food Administration) detected Listeria monocytogenes in two packs of cold-smoked salmon.

L. monocytogenes was identified at 240 CFU/g in chilled cold smoked salmon.

Raw milk sucks and is stupid: New Zealand edition

Batches of a brand of raw milk that is delivered in parts of the South Island is being recalled because it might contain Listeria monocytogenes.

The Government’s food safety regulator, the Ministry of Primary Industries, has issued the recall notice on Sept. 1, which applies to certain batches of Go Farming Ltd’s raw – unpasteurised – drinking milk.

The affected products are one litre bottles in baches 32, 33 and 34, with use-by markings of August 18, 20 and 21.

The ministry said the milk is sold online and is collected at the farm or delivered in the Southland and Queenstown regions.

Why some Listeria strains survive good food hygiene standards

Listeria is a nasty bug. With a fatality rate of almost 30 per cent – for those virulent strains – the litanany of outbreaks and its terrible toll are well-known to food safety types.

But why, despite high standards of cleanliness and hygiene in the food industry, bacteria such as Listeria monocytogenes can still be found in the food processing environment. In a study published in Applied and Environmental Microbiology, a team of researchers from Vetmeduni Vienna has now shown that certain Listeria strains take refuge on an island.

An “islet” of two genes located in one area of the genome increases the bacteria’s survival under alkaline and oxidative stress conditions. The researchers were able to identify the two genes as a functional unit termed a “stress survival islet”. Understanding this genetic “lifesaver” can help develop new strategies for food safety.

Listeria monocytogenes is a foodborne pathogen that colonizes and reproduces on diverse food products including cheese or meat. Without proper food hygiene, it represents a health risk. The hygiene standards in food production chains, therefore, are quite high. But Listeria is known for its ability to survive in environmental niches in which other microorganisms cannot.

The key to the bacteria’s survival is its adaptability and persistence in stress situations. Certain genetic mechanisms allow L. monocytogenes to react to and block the effects of cleaning solutions and disinfectants. Researchers from the Institute of Milk Hygiene were able to decipher this function for two of the food pathogen’s genes. They showed that these genes form a functional unit that ensures the bacteria’s survival despite the hygiene standards in the food production industry.

Hypervariable, i.e. easily changeable, regions of the genome contain genetic inserts that help Listeria survive. “These inserts include a unit of gene sequences, the stress survival islet 1 (SSI-1), a ‘genomic island’ that helps the microorganisms to survive certain stress situations,” explains first author Eva Harter. “Depending on the specific bacterial strain, this region accommodates one of three different gene sequences whose function, with the exception of SSI-1, had so far not been known.”

The genes in the stress survival islet 1 confer the bacteria a high tolerance toward acidic, bile, salt and gastric stresses and were characterized years ago. This does not explain how the bacteria can survive the hygiene standards in the food processing industry, however, which involves different, namely alkaline and oxidative, stress situations for Listeria. The researchers therefore concentrated on two neighbouring gene sequences within the same hypervariable region and were able to identify these as the genomic islet that acts as a lifesaver for certain Listeria monocytogenes strains in these situations.

The expression of the two genes and of the proteins which they code is increased during alkaline and oxidative stress. They must therefore have a different function than the genes belonging to the SSI-1. “We were able to assign a function to the two genes. The first gene is a transcriptional regulator, which in certain situations regulates the frequency and activity of the second protein. The second is a protease, an enzyme that breaks down other proteins. Proteases help bacteria break down unfunctional proteins that are created during stress situations,” says Harter.

“If the regulator is not active, then there is no protease. Without the protease, Listeria monocytogenes has a harder time compensating oxidative stress. The two genes therefore make up a functional unit, specifically the stress survival islet SSI-2,” says study director Kathrin Rychli. This islet is predominantly found in L. monocytogenes strains that are specialised for food and food processing environments.

“We were able to identify a specific genome type in which the SSI-2 sequence is always present,” explains Rychli. “This sequence type, ST121, is found almost exclusively in food and the food processing environment and hardly ever in clinical isolates. In strains forming part of the ST121 group, SSI-2 is highly conserved i.e. completely identical.” SSI-2 thus appears to be niche-specific. Most Listeria strains found in clinical isolates do not have SSI-2.” Through the discovery of the new stress survival island, the researchers, with project funding provided by the Austrian Science Fund (FWF), were able to describe an important survival strategy of foodborne Listeria. “Knowing the genetic mechanism, allows you to think about new strategies for food safety,” says Rychli.

More information: Eva Harter et al. Stress Survival Islet 2, Predominantly Present in Listeria monocytogenes Strains of Sequence Type 121, Is Involved in the Alkaline and Oxidative Stress Responses, Applied and Environmental Microbiology (2017). DOI: 10.1128/AEM.00827-17

Stress survival islet 2, predominantly present in Listeria monocytogenes strains of sequence type 121, is involved in the alkaline and oxidative stress responses

Appl. Environ. Microbiol. August 2017 vol. 83 no. 16

Eva Harter, Eva Maria Wagner, Andreas Zaiser, Sabrina Halecker, Martin Wagner and Kathrin Rychli

doi: 10.1128/AEM.00827-17

http://aem.asm.org/content/83/16/e00827-17

The foodborne pathogen Listeria monocytogenes is able to survive a variety of stress conditions leading to the colonization of different niches like the food processing environment. This study focuses on the hypervariable genetic hot spot lmo0443 to lmo0449 haboring three inserts: the stress survival islet 1 (SSI-1), the single-gene insert LMOf2365_0481, and two homologous genes of the nonpathogenic species Listeria innocua: lin0464, coding for a putative transcriptional regulator, and lin0465, encoding an intracellular PfpI protease. Our prevalence study revealed a different distribution of the inserts between human and food-associated isolates. The lin0464-lin0465 insert was predominantly found in food-associated strains of sequence type 121 (ST121). Functional characterization of this insert showed that the putative PfpI protease Lin0465 is involved in alkaline and oxidative stress responses but not in acidic, gastric, heat, cold, osmotic, and antibiotic stresses. In parallel, deletion of lin0464 decreased survival under alkaline and oxidative stresses. The expression of both genes increased significantly under oxidative stress conditions independently of the alternative sigma factor σB. Furthermore, we showed that the expression of the protease gene lin0465 is regulated by the transcription factor lin0464 under stress conditions, suggesting that lin0464 and lin0465 form a functional unit. In conclusion, we identified a novel stress survival islet 2 (SSI-2), predominantly present in L. monocytogenes ST121 strains, beneficial for survival under alkaline and oxidative stresses, potentially supporting adaptation and persistence of L. monocytogenes in food processing environments.

Sprouts still suck: FDA sampling shows sprouts a problem

There’s a reason Walmart and Costco and Kroger stopped selling raw sprouts: they suck, meaning that, like raw milk, they cause a disproportionate percentage of illness based on low consumption rates.

The U.S. Food and Drug Administration wrote in a recent report sprouts are especially vulnerable to pathogens given the warm, moist and nutrient-rich conditions needed to grow them. From 1996 to July 2016, there were 46 reported outbreaks of foodborne illness in the U.S. linked to sprouts. The U.S. outbreaks accounted for 2,474 illnesses, 187 hospitalizations, and three deaths (and, tragically, many more in Canada, Australia, Japan and Europe).

A table of sprout-related outbreaks is available at http://barfblog.com/wp-content/uploads/2016/02/Sprout-associated-outbreaks-2-23-16.xlsx.

From the executive summary:

The U.S. Food and Drug Administration (FDA) set out to collect and test sprouts in 2014 as part of a new proactive and preventive approach to deploying its sampling resources with the ultimate goal of keeping contaminated food from reaching consumers.

The new approach, detailed in the Background section of this report (page 4), centers on the testing of a statistically determined number of samples of targeted foods over a relatively short period of time, 12 to18 months, to ensure a statistically valid amount of data is available for decision making. This approach helps the agency determine if there are common factors – such as origin, season, or variety – associated with pathogen findings.

The FDA issued the sprouts assignment in January 2014 under its new sampling model. The assignment targeted sprouts at three points in the production process (seeds, finished product and spent irrigation water), with the aim of collecting and testing 1,600 samples to determine the prevalence of select pathogens in the commodity. As background, the FDA designed its sampling plan such that if contamination of one percent or greater was present in the commodity, the agency would detect it. The FDA monitored the assignment closely to gather lessons learned and make changes to its sampling procedures if needed to address trends or food safety issues. About one year into the assignment, the FDA decided to stop its collection and testing at 825 samples because it had already collected samples on more than one occasion from many of the sprouting operations known to the agency and its state partners. The sample set acquired was sufficient for the FDA to estimate the bacterial prevalences in the commodity with a 95 percent confidence interval of 0% to 2% for a one percent contamination rate.

The FDA tested only domestically grown sprouts for this assignment because virtually all sprouts eaten in the United States are grown domestically due to the commodity’s delicate nature and relatively short shelf-life. Of note, the industry features a preponderance of relatively small operations.

The FDA tested the sprout samples for three pathogens: Salmonella, Listeria monocytogenes and Escherichia coli (E. coli) O157:H7. Based on the test results, the FDA found the prevalence of Salmonella in the finished product sprouts to be 0.21 percent. The agency also found that the prevalence of Salmonella in seeds (2.35%) was significantly higher than in finished product (0.21%) and in spent irrigation water (0.54%). Based on the test results, the FDA found the prevalence of Listeria monocytogenes in the finished product to be 1.28 percent. There was no significant difference in the prevalence of Listeria monocytogenes based on point in the production process. None of the samples tested positive for E. coli O157:H7. The agency did not test seed for E. coli O157:H7 due to limitations associated with the test method.

Among the FDA’s other findings, the agency found most of the positive samples at a small number of sprouting operations. Specifically, the FDA found violative samples at eight (8.5%) of the 94 sprouting operations visited for purposes of this assignment. The fact that the agency found multiple positive samples at some of these operations underscores the need for sprouting operations to comply with the agency’s Produce Safety Regulation (published November 2015), which seeks to prevent outbreaks of foodborne illness and improve sprout safety.

To address the positive samples, the FDA worked with the firms that owned or released the affected product to conduct voluntary recalls or to have their consignees destroy it, and then followed up with inspections. Of particular note, this sampling assignment helped detect and stop an outbreak of listeriosis while it still entailed a small number of cases, as described in the Public Health Impact section of this report (page 14). This assignment also prompted six product recalls.

The FDA will continue to consider microbial contamination of sprouts and how best to reduce it. Such contamination remains a concern to the FDA given the aforementioned outbreak and the recalls initiated. Going forward, the FDA intends to inspect sprouting operations to ensure they are complying, as applicable, with the Produce Safety Rule, which includes new requirements for sprouts growers. The agency has no plans to conduct additional large-scale sampling of sprouts at this time but may sample the commodity in accordance with its longstanding approach to food sampling, which centers on (but is not limited to) the following criteria:

  • A firm has a previous history of unmitigated microbial contamination in the environment (e.g., human illness, recalled or seized product, previous inspectional history, or environmental pathogens without proper corrective actions by the facility), or
  • Inspectional observations that warrant collection of samples for microbiological analyses.

The complete report is available at https://www.fda.gov/downloads/Food/ComplianceEnforcement/Sampling/UCM566981.pdf?source=govdelivery&utm_medium=email&utm_source=govdelivery

Listeria in the news again

 

Food company Ready to Eat has announced a Listeria outbreak in several of their pre-packaged meals.
Ready to Eat, which produces ‘Muscle Fuel’ pre-made meals, said the meals affected are the ‘Vegetarian Chickpea and Pumpkin Rosti on Spinach Salad’ and the ‘Turkish Style Chicken & Rice’ with best before dates of August 4th, August 5th, August 6th, 2017.
Other meals are unaffected, the company says.
Any customers in possession of one of the affected meals are being urged to discard it immediately.
In a statement, Ready to Eat CEO Hamish Coulter said they were horrified when they received the news.
“To learn that one of our trusted produce suppliers has let us down is extremely disappointing.”
The Hamilton-based company was informed on Friday afternoon that its supplier Vegeez had returned a positive result for Listeria in one of its recent batches of cabbage.
On Friday evening the company contacted the 139 customers affected.
Vegeez general manager Glen Reid said it had taken full responsibility for the “very rare” event.
Mr Reid said in total there were 15 companies supplied with the affected cabbage, but all other companies managed to dump the product before using it.
Mr Coulter apologised to the company’s customers and said they were putting in measures to ensure this did not happen again.
The company has discontinued the use of coleslaw for the foreseeable future.
If any customer has consumed what they believe to be a contaminated meal they are advised to seek medical advice.
All customers will be contacted again this week with refunds issued.

I stumbled across an interested paper published in the Journal of Food Protection in February 2017 investigating the fate of Listeria monocytogenes , pathogenic Yersinia enterocolitica , and Escherichia coli O157:H7 gfp+inoculated in low numbers into ready-to-eat baby spinach and mixed-ingredient salad (baby spinach with chicken meat).

A quick synopsis of the study showed that when mixed-ingredient salad was stored at 8°C during shelf life, only L. monocytogenes increased significantly, reaching 3.0 log CFU/g within 3 days. The 8°C reflects maximum refrigerator temperature storage in Sweden.

In plain baby spinach, only pathogenic Y. enterocolitica populations increased significantly during storage for 7 days, and this was exclusively at an abuse temperature (15°C). Thus, mixing ready-to-eat leafy vegetables with chicken meat strongly influenced levels of inoculated strains during storage. 

The authors then translated the numbers into risks of infection. The risk of listeriosis (measured as probability of infection) was 16 times higher when consuming a mixed-ingredient salad stored at 8°C at the end of shelf life, or 200,000 times higher when stored at 15°C, compared with when consuming it on the day of inoculation. They conclude that efforts should focus on preventing temperature abuse during storage to mitigate the risk of listeriosis.

Söderqvist K1, Lambertz ST1,2, Vågsholm I1, Fernström LL1, Alsanius B3, Mogren L3, Boqvist S1. Fate of Listeria monocytogenes , Pathogenic Yersinia enterocolitica , and Escherichia coli O157:H7 gfp+ in Ready-to-Eat Salad during Cold Storage: What Is the Risk to Consumers? J Food Prot. 2017 Feb;80(2):204-212. doi: 10.4315/0362-028X.JFP-16-308.