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  • BarbaraCorreiaFaustino 3:48 pm on November 20, 2015 Permalink | Reply
    Tags: Cheese, Dairy, , , Listeria, , ,   

    Another multistate Listeria outbreak: this time from contaminated soft cheese 


    Recalled soft cheese products. Source: CDC

    An outbreak regarding soft cheese contaminated with Listeria monocytogenes finally arrived to a conclusion after five years of investigation. Starting in June 2010, thirty cases of listeriosis caused by the consumption of a specific type of cheese happened throughout the United States. Most of the cases were reported in California, but there was also a great number of cases happening specially in the eastern portion of the country, occurring in nine other states. According to the Center for Disease Control and Prevention, aside from California, there were also cases in Colorado, Illinois, Massachusetts, Michigan, New York, Ohio, Tennessee and Washington, and overall the outbreak resulted in 28 hospitalizations and 3 deaths, two in California and one in Ohio. Five illnesses were pregnancy-related, and one resulted in miscarriage.

    The Center for Disease Control and Prevention was able to link all those cases together using whole genome sequencing, which is a molecular subtyping method that is recently becoming more used by publich health authorities to identify foodborne pathogens. This method relies on sequencing the nucleic acid of the target microorganism and detecting the differences in that nucleic acid sequence.


    People infected with the outbreak strains of Listeria monocytogenes by contaminated soft cheese. Source: CDC

    Whole genome sequencing, as its name suggests, is a method that provides a nearly complete sequencing of bacterial nucleic acids, and that is what makes it a very accurate method, since it becomes much easier to compare and differentiate between serotypes of a specific bacteria. The first generation was not very user-friendly for the detection of foodborne illnesses outbreaks, as it was a very time-consuming, labor-intensive and expensive method. However, nowadays the development and improvement of next-generation sequencing methods have made these tools more available and affordable for laboratories, making it easier to use them routinely and ensuring not only precise, but also fast results, and at a reasonable cost. These methods are rapidly becoming more accepted by public health and regulatory agencies, and in the next few years they will probably replace the most commonly used method currently, which is pulsed-field gel electrophoresis (PFGE). Compared to the latter, whole genome sequencing methods have a higher discriminatory power for outbreak detection and allow for the sequencing of different pathogens in the same batch.

    The whole genome sequencing methods provide better discrimination between the subtypes, and therefore it can distinguish isolates that have a similar or equal PFGE profile, therefore improving the detection of a possible outbreak. This is what happened in this case, as the public health agencies could not properly connect all the cases that happened throughout the country with only one pathogen for over five years, and the whole genome sequencing showed that five rare DNA fingerprints of Listeria monocytogenes were related, connecting serotypes identified in this last August with serotypes found in the cases from around five years ago.

    The types of cheese involved in this outbreak were soft cheese, including Middle Eastern, Eastern European, Mediterranean and Mexican-style cheeses. The contaminated products likely responsible for the outbreak were from the brands Karoun, Arz, Gopi, Queso Del Valle, Central Valley Creamery, and Yanni, all of which were manufactured by Karoun Dairies, Inc. This company announced a voluntary recall of the products from those brands and stopped the production of other cheese products that might be contaminated with Listeria on September 16, 2015.

    Even though the incident was not very recent, a lot of restaurants and people may still have cheese products from those brands as the recall happened this year, and they are advised not to serve or consume these products as they may be contaminated with Listeria monocytogenes. It is very important that people don’t consume them, as listeriosis is a very severe disease, specially for children, the elderly and immunosuppressed population.

    Centers for Disease Control and Prevention. (2015). Multistate Outbreak of Listeriosis Linked to Soft Cheeses Distributed by Karoun Dairies, Inc. (Final Update). Retrieved from: http://www.cdc.gov/listeria/outbreaks/soft-cheeses-09-15/index.html

    Zuraw, L. (2015). Final Update: 3 Deaths, 30 Illnesses in Outbreak Linked to Soft Cheese. Retrieved from: http://www.foodsafetynews.com/2015/10/1-death-24-illnesses-in-listeria-outbreak-linked-to-soft-cheese/

    Wiedmann, M. (2015). Use of Whole-Genome Sequencing in Food Safety. Retrieved from: http://www.foodsafetymagazine.com/magazine-archive1/junejuly-2015/use-of-whole-genome-sequencing-in-food-safety/

    • cvalencia 10:47 pm on December 3, 2015 Permalink | Reply

      I don’t really consume a lot of soft cheeses, but it is interesting to know that there is a risk associated with it. Listeriosis is a very serious problem, especially for high-risk individuals (immunocompromised people and pregnant women). I heard of a case where a mom-to-be had a miscarriage because of eating soft cheese contaminated with Listeria, while on vacation.. Sad how these things can happen, so everyone should be aware of such risks.

    • Carissa Li 2:58 am on December 13, 2015 Permalink | Reply

      It is pretty cool how we can still investigate the same pathogen DNA from 5 years ago to identify its type using whole genome sequencing. As we all know, soft cheese is under category 1 according to the regulation from Health Canada, so it can grow throughout the stated shelf life. Listeria is known to be tolerant at low temperature, that’s why it is not surprising that it can grow on soft cheese. This case happened around 5 years ago so I think the risk of having Listeria contaminated soft cheese from this industry is not that high now if no new cases occur after that. But of course being caution is priority to not having any chance of getting sick!

    • MichelleLui 9:05 pm on December 18, 2015 Permalink | Reply

      Good summary of recalled soft cheese and how it relates to the techniques learned in class. Soft cheese belongs to Category 1 RTE foods. Consumers should be educated on the risk of consuming food listed under Category 1 RTE foods. Especially the high risk groups, such as children, elderly, pregnant women and people with weakened immune system.

    • mustafa akhtar 12:25 am on December 19, 2015 Permalink | Reply

      I am happy that the surveillance methods available in the industry are growing and developing. However, coupled with this, it is very important that we educate the public as well. It is not uncommon to hear of miscarriages happening because of consumption of soft cheese. As they say, prevention is better than cure.

  • Stephanie Chen 11:37 am on November 20, 2015 Permalink | Reply
    Tags: , , Listeria, ,   

    Listeria Seizes the Oppor-tuna-ty! Denmark investigates outbreak linked to smoked fish products 


    August 2015. Four people sickened by Listeria in fish products linked to fish company, Hjerting Laks, in Denmark. Earlier in May, five cases of Listeria with two deaths were detected in Denmark. Two out of the five were of the same strain of Listeria that caused 40 cases and 16 deaths in deli meats in 2014. Although the current outbreak is not linked to the one last year, one of the five in May was traced back to Hjerting Laks.

    Unique culprit. While all tested samples did not reveal to have Listeria above the accepted limit, the Danish Veterinary and Food Administration (DVFA) found that Listeria isolates from the patients and samples taken from the company’s production area, equipment, and official food samples gave a DNA match after whole genome sequencing. The Listeria monocytogenes ST6 sequence pattern specific to this outbreak has not been detected in samples from other sources.

    Suspect: smoked fish. The source of infection in exact products has not been confirmed by the DVFA, but smoked salmon was suspected due to patients’ common consumption prior to illness. An outbreak of Listeria connected to Hjerting Laks was related to smoked halibut in November 2014, after which changes in the production processes were made. Hjerting Laks states that the bacteria from the current outbreak may have originated from raw materials supplied by sub-contractor.

    “We have ordered the company to change its routines with regards to production and own-check scheme,” says Annette Perge, head of unit in the DVFA. “Tightened supervision” has been placed on the company, and DVFA has advised customers to discard related fish products or return them to the place of purchase.

    Listeria monocytogenes. A gram positive, facultative anaerobic bacterial species capable of causing infections that may lead to symptoms of fever, muscle aches, and diarrhea. Populations including those with compromised immune responses due to age, pregnancy, and disease are typically at higher risk for listeriosis, with possible deadly effects on fetus and newborn infants. The primary route of transmission for this pathogen is through food, and especially in ready-to-eat foods that support bacterial growth of L. monocytogenes.

    But smoked fish? Yes, smoked fish. Smoked seafood including salmon, trout, tuna, oysters, etc., are manufactured in two primary forms: cold-smoked and hot-smoked product. Typical temperatures used for cold-smoking (22-28°C) are inadequate to inactivate L. monocytogenes, but levels of the pathogen present on raw salted fish are usually reduced by 90-99% during the cold-smoking steps of salting, drying, and smoking. Hot-smoking involves initial drying at 30-40°C, then smoking at 60-70°C followed by a second drying procedure. However, products may be contaminated after both cold and heat treatment in the processing environment while products are sliced and vacuum packaged. It also doesn’t help that Listeria can grow at refrigeration temperatures and is relative resistant to heating, acidic and high salt environments, as well as other inhibitory compounds used on foodborne microorganisms.


    See diagram. Production process has multiple opportunities for contamination. (Where else do you see places for Listeria to sneak in?)


    Recommendations for persons at high risk (weakened immune system) from the CDC:

    • Do not eat refrigerated smoked seafood, unless it is contained in a cooked dish (e.g. casserole)
    • Refrigerated smoked seafood, such as salmon, trout, whitefish, cod, tuna, and mackerel, is most often labeled as “nova-style,” “lox,” “kippered,” “smoked,” or “jerky.” (These are typically found in the refrigerator section or sold at seafood and deli counters in grocery stores)
    • Canned and shelf stable tuna, salmon, and other fish products are safe to eat

    Reduce risk for listeriosis from smoked fish by… Using ready-to-eat foods as soon as possible (product’s shelf-life shortens upon opening the packing). And remember to practice good hygiene in the kitchen!


    News sources:

    Listeria traced to Hjerting Laks despite fish products passing tests. (Aug 2015). http://www.foodqualitynews.com/Food-Outbreaks/Denmark-investigates-four-Listeria-cases-linked-to-fish-producer

    Denmark investigates new Listeria outbreak. (May 2015). http://www.foodqualitynews.com/Food-Outbreaks/Listeria-sickens-five-and-a-factor-in-two-deaths


    Joint FAO/WHO Activities on Risk Assessment of Microbiological Hazards in Foods. Case Study: Listeria monocytogenes in Smoked Fish (including digram). Retrieved from http://www.fao.org/fileadmin/templates/agns/pdf/jemra/Listeria.pdf

    Report of the FAO Expert Consultation on the Trade Impact of Listeria in Fish. Retrieved from http://www.fao.org/docrep/003/x3018e/x3018e05.htm

    Center for Disease Control and Prevention. Whole genome sequencing. Retrieved from http://www.cdc.gov/listeria/pdf/whole-genome-sequencing-and-listeria-508c.pdf

    Center for Disease Control and Prevention. Tips for preventing Listeria poisoning. Retrieved from http://www.cdc.gov/ncezid/dfwed/pdfs/tips-preventing-listeria-508c.pdf

    Image retrieved from http://www.rivertea.com/blog/7-healthy-breakfast-recipes-for-every-day-of-the-week/

    • Michelle Ebtia 1:00 pm on November 29, 2015 Permalink | Reply

      This was a really interesting report! I do like smoked sockeye and always choose hot-smoked variety, however, after reading about the chances of cross-contamination post-production, I think I will avoid consuming them prior to further cooking and heating.
      Since the current measures seem to be rather ineffective, I did some research to find out about alternative methods for prevention and came across a paper that reports a novel approach in controlling the growth of Listeria spp on smoked salmon, through inoculating it with Carnobacterium maltaromaticum. The authors conclude that “the bioprotective culture C. maltaromaticum can extend the commercial shelf life of both hot and cold smoked salmon”, as it outcompetes the growth of the pathogen. However, I couldn’t find any reports of this method being put to practice by food manufacturers.

      Work Cited:
      Smith, D. (2012, July). Biopreservation: Control of Listeria monocytogenes Growth in Hot and Cold Smoked Salmon by Carnobacterium maltaromaticum CB1. In 2012 Annual Meeting. Iafp.

      • Jasmine Lee 2:02 pm on November 29, 2015 Permalink | Reply

        I really like the clever use of wordplay in your title. It highlights the opportunistic nature of Listeria monocytogenes to persist and grow in susceptible ready-to-eat foods. Given that L. monocytogenes is ubiquitous in the environment, I am not surprised that it would appear in fish, especially smoked salmon. There are Canadian regulations which require manufacturers to ensure sufficient lethality of their treatments and inactivation of their target microorganisms. If there are deviations in these standards, then the pathogen may remain and continue to be a problem. Furthermore, the smoking process is dependent on the smoke reaching the contaminated surface. The pathogen may be embedded in the flesh of the fish, where the smoke cannot make contact. Time and temperature abuse of the raw materials may also promote bacterial survival. As beautifully illustrated in your flowchart, I agree with the multiple routes of entry and carriers which contribute to the pathogen’s survival. The food matrix may be another factor since salmon is high in lipids. Fat is known to protect L. monocytogenes, which will present another challenge to eradicating this pathogen. As a consumer, I will probably reduce the consumption of this product or research more about the company before taking smoked salmon to the checkout.

    • AngeliMalimban 2:26 pm on November 29, 2015 Permalink | Reply

      I read a small article saying that Listeria does not normally survive the smoking process. However, it can still grow while being stored if it is done so improperly. It can grow heat-resistant endospores if it is not smoked to a high enough temperature either (source: http://foodsafety.wisc.edu/assets/pdf_Files/smokingyourcatch.pdf). Smoked fish can also be found in shelf-stable storage (I commonly see these at Canadian souvenir stores) where it is ready to eat. This can also have an equal risk of contracting L. monocytogenes, but there may be a common misconception that shelf-stable foods are safer to consume and that the likelihood of disease could be less.

      I actually LOVE smoked salmon, especially when I go get sushi (where they serve smoked salmon on top of sushi). It’s pretty scary because sometimes I just see the fish wrapped at room temperature on the sushi bar… it makes me wonder if it is actually refrigerated or left out there for the whole day. This is also consumed raw – and I should probably heat/cook it instead.

    • WinnieLiao 3:58 pm on December 3, 2015 Permalink | Reply

      First thing to point out is that your layout is easy to read and your wording is short and precise! I personally don’t like eating smoked salmon not only because of the fishy taste but also because of the salty and preservative content. The smoked salmon products I have seen in supermarkets are usually those vacuum packed. Just from looking at the product, I assume the producer processed their food by controlling water activity, using of preservatives and eliminating air. Knowing that Listeria is a relatively “resistant” bacteria that often is salt tolerant, dessication tolerant and facultative anaerobic, I can understand why it would survive so well in smoky salmon! Also another issue that comes to my mind, is that some First Nations people make their own homemade smoked salmon, which can be a possible food safety concern.

    • CindyDai 12:24 am on December 15, 2015 Permalink | Reply

      I agree what Winnie has said. There are a lot of other safety hurdles used in smoked fish industry to suppress pathogen growth. Lowering water activity, adding preservatives and vacuum packaging are all examples of other hurdles used. Since Listeria has high adaptation to tough environments, only multiple hurdles used simultaneously could ensure the effectiveness. However, as learned in lectures, sub-lethal treatments could cause increased resistance to other safety treatments, so the combination of safety hurdles must be well planned and proved by scientific test results.

    • Ya Gao 11:46 pm on December 15, 2015 Permalink | Reply

      The traditional preservation method, smoking, may not be safe for food processing if the raw material or the procedure after food processing is problematic. I love smoked salmon from deli area in Costco a lot personally. Although I cook them occasionally, I prefer eating them raw right away from the package. I will be more cautious in the future.

  • AngeliMalimban 7:06 pm on October 30, 2015 Permalink | Reply
    Tags: , , Listeria, , ,   

    Listeria Monocytogenes in Adolf’s Deli Meats and Whole Foods Curry Chicken 

    American Thanksgiving is coming up, which is a prime time for meat producers as they will be selling a lot of turkey, ham, chicken, and many other meats that most families traditionally consume on Thanksgiving. If families are tight for time to prepare food, or have a lot of people to prepare food for, some will resort to getting Ready-to-Eat meats from the deli, such as ordering deli turkey breasts or deli ham.
    With the purchase of ready-to-eat (RTE) meats comes the risk of Listeriosis, as RTE meats are one of the favourite breeding grounds for L. monocytogenes.

    On October 29th, 2015, and still currently, American consumers have been warned about meat that could be potentially contaminated with Listeria monocytogenes. This particular outbreak was attributed to smoked kielbasa, hams, Canadian Bacon, bone-in pork loins, and liverwurst that were produced on October 20th, 2015 that was produced by Adolf’s Meat Products in Connecticut. About 224 pounds of meat have been recalled.

    In another incident, a Whole Foods supplier in Massachusetts is recalling curry chicken products, such as their salad, salad wraps, and salad roll-ups that could also possibly have been infected with L. monocytogenes. Customers who have purchased these items are told not to consume them and to return the products straight to the store.
    This problem was confirmed during FSIS sample testing, although there have not been any cases or adverse reactions reported due to consumption of these meat products.

    L. monocytogenes favours growth in refrigerated to room temperature (4 to 37 degrees C), which is the reason why they are so prevalent in these meats that are eaten on their own without cooking. It is also present in many raw foods such as milk, ice cream, and produce. Despite this, most of the big outbreaks in Central/Eastern North America have been attributed to RTE meats. To put statistics into the prevalence of L. monocytogenes in the USA, 1600 illnesses and 260 deaths happen annually due to the contamination of food. Per 100,000 people, 0.26 cases are estimated. Despite these statistics, listeriosis has declined by 42% in 2013 compared to 1996-1998. An example of a major outbreak was the big Listeria outbreak at a Maple Leaf foods branch in Toronto in 2008, which resulted in 57 cases of illness and 23 deaths. This outbreak cost the company $20 million dollars, and 23 of their products were recalled. L. monocytogenes proved to be a forced to be reckoned with as the company had lost not only the money, but their image as well.

    In North America, Listeria is considered to be an increasing threat to human health due to antimicrobial resistance, its ability to grow in refrigerated temperatures, and its large prevalence in the environment. Listeriosis can be fatal in those who are elderly and those that are still young children. Luckily this was found before the outbreak actually had caused illness in a consumer, however, it is still early to tell as the outbreak was very recent.

    It is important that consumers understand that they must be vigilant when consuming RTE meats. Although hot dogs, luncheon meat (SPAM), and deli meats are convenient because they are already pre-cooked, the risk of contracting listeriosis is very real.
    Hopefully this thanksgiving, those who choose to purchase RTE meats to serve at dinner cook it very thoroughly past 40 degrees C. It is advised that they use thermometers and put it into the deepest part of the meat to ensure that this temperature is meat. If there are any leftovers (which is definitely bound to happen) they should divide them into shallow containers to promote rapid cooling.

    What do you think about this outbreak? Do you think that the government and companies generally do a good job in recalling products and preventing illnesses? How do you consume your RTE meats?







    • ayra casuga 3:57 pm on November 5, 2015 Permalink | Reply

      Interesting blog. I think because the meats are sold as “read-to-eat”, people usually do not think to apply more cooking preparations for it. I feel like thats what makes eating “ready-to-eat” foods so risky because we have to put a lot of trust to the food manufacturers that they’re consistently implementing stringent food safe procedures when preparing their ready-to-eat products. Especially because Listeria Monocytogenes is a very resistant bacteria.

    • Silvia Low 6:38 pm on November 8, 2015 Permalink | Reply

      Reading about listeria in RTE meats really scares me as i regularly purchase my lunches from places such as subway, deli stores, sandwich stores, etc. The employees working there seem to adequately clean up their stations but I dont think they understand why it is important that they clean it well or the repercussions that come from foodborne pathogens such as l.monocytogenes. Or maybe i’m wrong and theyve all been trained very thoroughly about common deli meat pathogens. Who knows.

    • EmilyLi 6:19 pm on November 10, 2015 Permalink | Reply

      This is an engaging blog post. I like how this instance didn’t cause any major problem in the population. This could be due to the rapid detection and efficient recall procedure from both the company and government to prevent any death and illness. I think the role that government plays in recalling food is very important. This is because that companies may not have enough resources to spread the word rapid enough, and I think with the government helps the recall process is faster. Also that many people trust government officials with providing legitimate facts. After learning about that ready to eat food are not the safest to be consume, I had been cooking some of the ready to eat products, such as ham. However some ready to eat food products such as salad, wouldn’t taste the same and as good if I cook it, so recently I been staying away from those foods.

    • WinnieLiao 10:45 am on November 18, 2015 Permalink | Reply

      I agree with Ayra about the fact that “ready-to-eat” “reminds” people that the meat is well prepared and that further cooking preparations are unnecessary. However this can probably contribute to why L.monocytogenes can be so prevalent in deli meats. Nowadays people are fond of sandwiches, since they are easy to make and “everything into one”. This gives rise to more opportunities for exposure. In terms of government, I think they have been doing quite a good job in quickly recalling the products and acting quick in the investigations. Even though there has been many outbreaks, I will continue to consume these products, and try my best to reduce the chances of getting foodborne illnesses by preventing the cross contamination of deli meats with other foods. Keep proper sanitation when handling the food and consuming it asap are also my goals!

    • CindyDai 5:27 pm on December 1, 2015 Permalink | Reply

      Outbreaks in RTE foods really caught my attention. Nowadays people are so used to the concept of “grab and go”. Consumers trust the safety of RTE foods and do not usually perform any more processing before consumption. Therefore, food vendors and government surveillance agents have huge responsibility to ensure food safety and establish an efficient problem-detecting system. As consumers, we should also try to prevent cross-contamination by separating RTE food from raw food. Any leftover RTE food products should be reprocessed or discarded.

    • CandiceZheng 3:31 pm on December 14, 2015 Permalink | Reply

      It is not surprised that RTE meats are the most favorable breeding grounds for L. monocytogenes, as RTE meats do provide an environment for Listeria growth, while people simply eat RTE meats without any further processing. Since Listeria are able to grow under refrigeration temperature, keeping deli meats in the fridge does not prevent the growth of Listeria at all. However, nowadays consumers trust the fridge so well and believe that proper refrigeration temperature would solve everything. As a consequence it is very essential to raise people’s awareness about this issue and especially for the immune suppressed population like pregnant women, further thermal processing of deli meat might needed to ensure food safety. As listeriosis in pregnant women would be a very serious issue.

  • csontani 1:13 pm on October 30, 2015 Permalink | Reply
    Tags: , Denmark, , Listeria, ,   

    Another Visit by Listeria in Denmark 

    In May 2015, Statens Serum Institut (SSI) detected another five cases of Listeria in Denmark. The five cases showed up in one week, which makes it unusual if there was only one source. The source of the cases is still undetermined; with deli meats being the most suspected, as it is the cause of last year’s outbreak. All five people had the underlying illnesses and two have died since.


    Listeria is one of the low-key food pathogen in Denmark, but it is considered to be one of the deadliest. The European Food Safety Authority (EFSA) declared that Listeriosis cases have increased by 8.6% between 2012 and 2013, and have been increasing for the past five years. Overall, the number of cases reported in Europe is low but the main concern would be the fact that each infection that occurred is the most severe and has the highest death rate.

    It seems that Listeria has been coming back to Denmark for the past 3 years. In September 2013, 5 people were diagnosed with Listeriosis and the case continued on until August 2014 where approximately 38 people were sickened and 15 deaths. This particular outbreak was considered to be the deadliest food pathogen outbreak in Denmark. The main cause of this outbreak was the contaminated deli meat used to prepare Rullepoelse (picture above). The company that distributed the deli meat was shut down after the source traced back to them last year, but has reopen again this year. However, the Danish Veterinary and Food Administration (DVFA) have ruled out that company as the source of this year’s outbreak.

    SSI stated that two out of the five people infected with Listeriosis this year are infected by the same strain that caused last year’s outbreak. As of now, the SSI is still trying to trace back the source for the cases they’ve found and is trying to sample the possible food source that they could think of. They have not found any more new cases and are hoping to not have another outbreak just like last year. However, with the current number of cases, it is very difficult for them to figure out the source of Listeria.

    In order for the health agency to trace back the source of the contamination, they need an adequate amount of cases to easily determine the source. This is kind of an issue for Denmark where in one year they would only detect a small amount of cases, which they can’t use to find the source easily, and the case would continue the following year with a greater number of cases.

    It might be possible that in the near future, the department responsible for food safety can create a better sampling and detection technologies that could help them to trace the source of contamination with a small amount of cases available. With your knowledge about Listeria, what solutions would you suggest them? Would you think that better detecting and sampling technologies would make a big difference to the country? Comment below!

    Denny, J., McLauchlin, J. (2008). HUMAN LISTERIA MONOCYTOGENES INFECTIONS IN EUROPE – AN OPPORTUNITY FOR IMPROVED EUROPEAN SURVEILLANCE. Retrieved from: http://www.eurosurveillance.org/ViewArticle.aspx?ArticleId=8082

    EFSA. (2015). Campylobacteriosis cases stable, listeriosis cases continue to rise, say EFSA and ECDC. Retrieved from: http://www.efsa.europa.eu/en/press/news/150128

    SSI. (2014). Listeria outbreak – suspected source: deli meats. Retrieved from: http://www.ssi.dk/English/News/News/2014/2014_08_listeria.aspx

    Whitworth, J. (2015). Denmark investigating new Listeria outbreak. Retrieved from: http://www.foodqualitynews.com/Food-Outbreaks/Listeria-sickens-five-and-a-factor-in-two-deaths

    Whitworth, J. (2014). Listeria from deli meat kills 12 in Denmark. Retrieved from: http://www.foodqualitynews.com/Food-Outbreaks/Joern-A.-Rullepoelser-closed-as-Denmark-investigates-Listeria-outbreak

    • shinnie 3:06 pm on October 31, 2015 Permalink | Reply

      Thank you for this blog post. It is interesting to compare the mortality rates of the same pathogen from different geographical areas– the mortality rate is much lower in the U.S. and in Canada as compared to Denmark. I wonder why? Perhaps it is because our health care system is better, or maybe our surveillance of pathogen is also more developed? I am assuming they are using a case-control study to identify the source of the outbreak –and the weaknesses of this source attribution method is evident in the Denmark outbreaks.
      I feel that people in Denmark should push the notion that high-risk people should avoid eating Category 1 foods all in all, although it limits the variety of the foods someone can consume. But, better safe than sorry right? Looking at the pathogen safety data sheets from PHAC, it is so interesting to note that outbreaks from Listeria Monocytogenes were from different food types in the past! For example, from vegetable products in the early 1980s, to dairy products in the mid 1980s and early 1990s, to ready-to-eat meat and poultry products in the late 1990s to early 2000s. How did that evolve?!?!

    • dgozali 8:51 pm on November 2, 2015 Permalink | Reply

      Perhaps one of the solutions for this problem is to have better food production practices and more routine quality checks in the processing facility. It is better to improve the prevention strategies in the production plant than to work backwards to determine the cause only after the outbreak has happened. Nevertheless, it is still important to improve on pathogen detection methods to trace the source of Listeria before more people fall ill.

    • elaine chan 1:15 pm on November 14, 2015 Permalink | Reply

      It is definitely unfortunate to hear that the number of reported Listeriosis is increasing throughout the years in Denmark. What I find interesting though is that the cause of the outbreak is from the same strain of Listeria, but from different sources. This could possibly suggest that this particular strain has better survivability; hence, it’s able to survive, persist and cause subsequent outbreaks in Denmark. I agree with dgozali’s idea on focusing to better improve the prevention strategies. Rather than waiting and trying to work backwards to determine the cause, which will cost more time and more outbreaks to determine the answer, it is more practical focus on what can actually be done, prevention. It will be important for food manufacturing facilities to implement more strict sanitization and processing conditions to ensure the elimination of Listeria survival. At the same time, it will also be equally important to improve sampling and detection methods at the food production level to ensure that if Listeria is present, it can be readily detected and subsequently stop production to prevent the outbreak.

    • flyingsquirrel 5:50 pm on December 2, 2015 Permalink | Reply

      If there were small outbreaks in two consecutive years of the same strain of Listeria, could the contamination been at a different level aside from the manufacturers? Perhaps there is something going on at the stores that sell the deli? I wonder what places they have checked for cross-contamination because if it is the same strain, there could likely be a common point of contact between all the deli meats involved.

    • Carissa Li 12:26 am on December 14, 2015 Permalink | Reply

      It is very surprising how Listeria is affecting Denmark compare to its influence on the US. From the outbreak investigation lecture we learnt that finding more cases is very critical since it helps us to understand more about the time frame, size and the source of contamination. I would say a better detection method will help the case a lot since it can help identify which food is being contaminated with Listeria and narrow down the suspecting food list.

  • cvalencia 11:48 pm on October 29, 2015 Permalink | Reply
    Tags: Listeria, ,   

    Multistate Listeria Outbreak from Contaminated Caramel Apples 


    It’s that time of the year when children (and children at heart) go out in their best costumes, knocking on neighbors’ doors with baskets full of candy in hand. It’s that time of the year when candy shops are full of consumers wanting to get their hands on sweet treats. A well-known treat for the fall and Halloween season is the candy apple: whole apples (usually Granny Smith apples) in sticks smothered with chewy caramel and colorful toppings. Never did it occur in any of our minds that such treats would be a source of illness: until now.

    In January 6, 2015, Bidart Bros., an apple producer from Bakersfield, California, recalled Granny Smith and Gala apples they produced from their facility. The firm did so after an inspection and testing of their facility showed contamination of Listeria monocytogenes. Three clients of Bidart Bros. who are caramel apple manufacturers (Happy Apples, California Snack Foods, & Merb’s Candies) also announced the recall of their products due to L. monocytogenes contamination. The Centers for Disease Control and Prevention worked with the U.S. Food and Drug Association in the investigation of the outbreak. Listeria was isolated from infected individuals, and analysis was conducted through pulsed field gel electrophoresis (PFGE) and whole genome sequencing. These laboratory methods confirmed the presence of the pathogenic L. monocytogenes in the infected individuals.

    Map of persons infected with the outbreak strains of Listeria monocytogenes, by state of residence, as of December 29, 2014 (n=32)

    Source: CDC

    The Listeria contamination caused a multistate outbreak, reaching 12 states across the United States. A total of 35 cases has been reported, with 34 cases causing hospitalization. Based on the report of the Centers for Disease Control and Prevention, 11 illnesses were pregnancy-related, while 3 cases involved meningitis in children (aged 5-15 years old) who consumed the contaminated caramel apples. A total of 7 deaths were reported, with Listeriosis contributing to 3 of those deaths.

    So how did L. monocytogenes survive and grow in caramel apples, a food in which the pathogen is not expected to grow? At the outset of the Listeria outbreak, many assumed that the cause of growth was the caramel coating on the apples, or the coating process itself. Although testing of the Bidart Bros. apple packing facility revealed the presence of L. monocytogenes on surfaces that directly contacted the apples, further investigation by experts was conducted to understand the mechanisms through which Listeria was able to grow on the caramel apples.

    Dr. Kathleen Glass, Associate Director of the Food Research Institute in the University of Wisconsin, conducted a study to replicate the process and conditions undergone by the caramel apples during production.Dr. Glass hypothesized that inserting sticks into the apples released juice on the otherwise dry surface of the fruit, and subsequent coating with caramel trapped the pathogenic bacteria inside the finished product. This, in turn, created a favorable environment for L. monocytogenes to grow in the caramel apples. In the experiment, apple samples were inoculated with L. monocytogenes before dipping in caramel. One group contained sticks inserted into the apples while the other group did not have sticks inserted. Experimental results revealed that both groups of stick-punctured caramel apples (refrigerated and non-refrigerated) showed significantly greater L. monocytogenes growth than non-punctured caramel apples. This study indicates that extra precautions need to be taken in processing of such foods, since the interface between different components of the product may provide favorable conditions for growth of pathogenic bacteria. Even though foods are considered to be unfavorable for pathogen survival and growth, food safety measures still need to be taken to prevent future outbreaks.

    Listeria monocytogenes has an infectious dose of 105 to 107 CFU in high risk individuals (eg. children, pregnant women, older populations, and immuno-compromised individuals). The pathogen is known to have adaptations to survive in the environment. L. monocytogenes is able to grow at refrigeration temperatures, and has the ability to form biofilms, thereby enhancing the pathogen’s survival in the environment. Listeriosis is the bacterial infection caused by the pathogen L. monocytogenes. Symptoms of the disease include diarrhea, fever, muscle aches, confusion, and loss of balance. Severe “invasive” cases of listeriosis may result in bacteremia, septicemia, and meningitis in high risk individuals.

    How do you think this incident affects the apple industry in Canada? Should we now be extra careful in eating caramel apples? Comment below and share your thoughts!

    Click on the “Cinnamon Caramel Apple Pumpkin” photo (from Darla of Bakingdom.com) to grab the recipe and have a great Halloween!

    Interested in knowing how caramel apples are commercially made? Watch the video below:


    Andrews, J. (2015). IAFP 2015: Experts May Have Determined How Caramel Apples Caused That Listeria Outbreak.

    Centers for Disease Control and Prevention. (2015). Multistate Outbreak of Listeriosis Linked to Commercially Produced, Prepackaged Caramel Apples Made from Bidart Bros. Apples.

    Glass, K.A., Golden, M.C., Wanless, B.J., Bedale, W., & Czuprynski, C. (2015). mBio: Growth of Listeria monocytogenes Within a Caramel-Coated Apple Microenvironment. American Society for Microbiology.

    Ryser, E.T. & Marth, E.H. (eds.). (2007). Listeria, Listeriosis, and Food Safety (3rd Edition). Boca Raton, Florida: Taylor & Francis. pp 85-110.

    • ayra casuga 11:38 am on October 30, 2015 Permalink | Reply

      I like how you incorporated Halloween in your blog! This is a similar topic discussed in lecture on L. Monocytogenes. Especially the idea that a wooden stick puncturing the apples may have been the biggest determinant in Listeria growth. I find it interesting that having that stick punctured in the apple can enhance Listeria’s survival to a degree where it has caused such a negative impact on the population.

      • laurenrappaport 4:17 pm on October 31, 2015 Permalink | Reply

        Super interesting to learn a bit more in detail about something that was mentioned in class! Candy apples are not something people usually consider a risky food to eat so its a bit concerning how much harm this contamination has caused. Although a large chunk of people who were harmed by this contamination were either pregnant or immunocompromised, everyone still needs to be careful about the foods they are eating. I dont think however that the Canadian market will be affected by this outbreak. Most people’s food choices are not that heavily influenced unless an outbreak is occurring close to them or directly affects them in some way. Furthermore, if we became concerned with every food that has been linked to an outbreak or has the potential to be contaminated I think there would be very little food left for us thats safe to eat!

    • TamaraRitchie 4:39 pm on October 31, 2015 Permalink | Reply

      It is interesting how one small step in the Candy apple production could cause a food safety issue. Its important as students in the food science field to understand how every person, thing and process in a food plant could be a chance for bacterial contamination. I found it very interesting that the small amount of juice that is expelled during the process when the sticks are pushed into the apples was enough to allow for growth of Listeria on the Candy apples.

      I do not think this will have much effect on the Candy apple industry in Canada. I do not think a lot of people hear about food recalls outside their country. I think if we tried to avoid all foods that have had outbreaks in the past their would be very little we would eat. I think it is important for the general population to be aware of food safety risks, and the fact that any prepared foods may carry a food safety risk, although in countries like Canada these risks are monitored and should be small.

    • BarbaraCorreiaFaustino 11:10 am on November 2, 2015 Permalink | Reply

      I really liked how you related your post to Halloween! Even though it’s surprising that 35 cases were reported, with most of them resulting in hospitalizations, I also believe that this outbreak won’t have a big effect on the Canadian apple industry, especially since the outbreak didn’t happen in Canada. I believe that the Canadian apple producers and authorities should be worried about how the wooden stick puncturing process can enable L. monocytogenes survival and growth, but I don’t think the general public will be very concerned about this topic.

    • KristinaRichmond 5:25 pm on November 6, 2015 Permalink | Reply

      Great article! I think this case is a good example of how well L. monocytogenes can adapt and survive in unexpected places. Hopefully people in the food industry can learn from this outbreak and consider how important food safety practices are even in supposedly low-risk foods. I think this is especially important regarding listeria since it can have such devastating effects in vulnerable populations. In this case it’s disturbing since caramel apples would be particularly attractive to children.

    • elaine chan 2:04 pm on November 14, 2015 Permalink | Reply

      Very interesting article! It’s unfortunate that a sweet treat like this, adored by children and adults, can result in an outbreak nightmare like this. I could be wrong, but what I am curious about is how a treat that’s been considered safe for consumption throughout all the years that it’s been available for consumption, is now causing problems in terms of food safety. Could this be an indicator of an increased survivability of the Listeria species? Another point that I’m curious about is the time of consumption and storage in relation to pathogen survival and growth. Since inserting sticks into apples introduces a favourable environment for pathogen growth, and the pathogen requires time to replicate and grow to infectious dose, would consuming the apple product right after production decrease the possibility of infection? And so I wonder, would it be safer for consumers to purchase freshly made caramel apples as opposed to pre-made ones? Overall, I don’t think that this outbreak would negatively influence Canada’s apple industry since this outbreak is specific to the production process of caramel apples. However, I do think that the individuals with higher risk of infection, such as children and pregnant women, should be cautious when consuming such products.

  • FeliciaYuwono 11:49 pm on October 25, 2015 Permalink | Reply
    Tags: Blue Bell, Ice Cream, Listeria, , , ,   

    Listeria Outbreak Associated with Blue Bell Ice Cream 

    Blue Bell Creameries recently did product recall for the first time in their 108 years of company’s history caused by an outbreak of Listeria monocytogenes. There were in total 10 cases in 4 states & 3 deaths affected by the outbreak. They have 3 production facilities and all of them were contaminated with Lm: one in Texas (which is the headquarters), and two auxiliary production lines in Oklahoma and Alabama. In this post, I’m focusing on what happened in the Oklahoma facility.

    The first 5 Listeriosis cases that were reported in Kansas early March 2015. They were all hospital inpatients and immunocompromised, and 3 of them actually died, which made up the total deaths for this outbreak. In late March 2015, using PFGE and Whole Genome Sequencing, Kansas Department of Health and Environment found out that the same strains of Lm found in the patients were traced back to unopened Blue Bell Creameries’ 3 oz. Institutional/Food Service Chocolate Ice Cream cups served in the hospital, which were manufactured in the Oklahoma production facility. Interestingly, this product was distributed to 23 states and only sold in schools, nursing homes, and hospitals, which mainly accomodate individuals at risk. This suggests that there were probably unreported cases of listeriosis linked to the Blue Bell Creameries’ products.


    In May 7, 2015, the FDA released findings from Blue Bell Creameries’ production facility in Oklahoma. In this report, there are 12 observations being made but I’m only going to outline several points.


    This report mentions that the Oklahoma Department of Agriculture, Food, and Forestry established a requirement of 20 CFU/mL of Lm or less in finished products of frozen dairy desserts. In March 2015, 275 CFU/mL Lm was found in the finished product half-gallon Dutch Chocolate Ice Cream, more than thirteen times the recommended levels. Now, if we assume that there is 275 CFU/mL of Lm in a 3 oz. (88mL) Institutional/Food Service Chocolate Ice Cream cup, then there is in total 24,200 CFU of Lm in one cup. However, several hospital patients fell ill after consuming the particular product, which means that the amount of Lm in that product is at least at an infectious dose of 0.1 to 10 million CFU for at risk individuals. Based on these assumptions, Lm might continue to grow under freezing temperatures, but more research needs to be done on this subject. Another possibility is that some finished products of the chocolate ice cream already had enough Lm in it to infect at risk individuals, therefore any more Lm growth would not make any impact.


    This report also mentions that the plant’s production line is not designed to prevent cross-contamination from drippings and condensate from pipes and tank lids. The lids on top of the tanks containing post-pasteurized Dutch Chocolate Ice Cream were not closed tightly, hence condensate from another product line installed horizontally right above it drips into the tanks, which makes a potential source of Lm contamination. Additionally, a worker was observed spraying the top of the lids and switching lids between other post-pasteurized Dutch Chocolate Ice Cream tanks, which may contribute to Lm cross-contamination in the tanks. The rest of the report states that lack of employee hygiene and inadequate facilities for cleaning and sanitizing equipments might be some contributing factors to the growth of Lm in their products.


    Now, if you were to be part of Blue Bell Creameries’ quality control team at the Oklahoma production facility, what would you do? What recommendations would you offer to make the production line safer?

    • wen liao 9:19 am on October 26, 2015 Permalink | Reply

      It is definitely amazing how Listeria can survive and still being infectious in made ice-creams, considering it is an environment low in temperature and water activity. As we have discussed in class before, ice-cream is considered as one of the products where there should be no growth of Listeria what’s so ever. Thus the problem here definitely are due to the ingredients. Since ice cream production are considered as low Listeria risk, people work here might pay less attention on sampling and checking on listeria load, which might be the cause of the problem. Therefore, it is important that people working in food industry pay extreme attention on what they are doing to ensure food safety.

    • YaoWang 1:39 pm on October 27, 2015 Permalink | Reply

      We all know that Listeria is a main concern in ready to eat meat products, but it’s amazing to know that it can be a problem even in ice cream. Normally, since ice cream provides low temperature and low water activity, we assume there shouldn’t be Listeria present. I’m very curious about how listeria can survive and may even grow under such environment. But this recall reminds us that even though the food is of less possibility of certain microbial contamination, the manufacture must still follow proper handling techniques to avoid potential cross contamination.

    • amreenj 7:18 pm on October 28, 2015 Permalink | Reply

      Wow! As we have previously learned, ice cream is considered a Category 2B food, which is a ready to eat foods in which Listeria monocytogenes cannot grow. So the occurrence of Lm. in ice cream is surprising. Im interested to see if they can actually trace the source of the Lm. and report back their findings. The worse part is that it was given to individuals whose immunity is low (ie. high risk groups- longer term care facilities, hospitals) and thus the impact could have been so much worse. Having preparing sanitation and handling protocols is imperative to recurring the risk of food borne illnesses. As we can we that failing to do so can lead to contamination in even the most unlikely of places/foods!

    • mustafa akhtar 10:18 am on October 29, 2015 Permalink | Reply

      I am so surprised that they ONLY distributed this product to schools, nursing homes, and such. I wonder if any research was put into developing the product at all. If not, then atleast the product shouldn’t have been sent to places where immunocompromised people reside.

    • Susanna Ko 4:55 pm on October 29, 2015 Permalink | Reply

      I think it shows that people must be diligent when deciding on the food menu for certain populations such as elderly or immunocompromised. Also, it’s surprising that the company survived so far without failing an inspection. Was it because it was categorized as a low-risk food, meaning that it is inspected less frequently? Also, how many spontaneous abortions occurred from pregnant women consuming this product because they wanted to enjoy a special treat? It’s really unfortunate.

    • Stephanie Chen 6:00 pm on November 19, 2015 Permalink | Reply

      It is really quite sad that even a delicious treat such as ice cream can harbor foodborne pathogens, and with a company that must have had good reputation for so many decades. Bluebell also explained that the reason they did not test their ice cream after positive tests of Listeria in their plant in previous years was because Listeria was found on non-food surfaces that did not come in contact with ice cream products. It was also not required at the time to report Listeria findings to the FDA. This shows that practices in the industry need to be routinely evaluated and food safety regulations should be strictly enforced.

    • meggyli 10:11 pm on November 27, 2015 Permalink | Reply

      Another interesting class-related blog! We learned in class that ice cream belongs in a category 2B food where the chances of Listeria growth/contamination is really rare. Similar to the above caramel apple blog, this just goes to show that we can never be too careful. It always causes the most damage to our health and economy when it’s the most unexpected food that contracts a pathogen. Who would have thought that something like ice cream which inhibits most microbial growth due to its cold storage temperature could cause something as severe as stillbirths & spontaneous abortions.

    • Mandy Tam 9:02 pm on December 1, 2015 Permalink | Reply

      I think a lot of time when people think of outbreak in related to Listeria Monocytogenes are related to ready to eat meat or deli product. I think this article provides a great example that Listeria growth could happen in other foods as well.
      North America very emphasis in HACCP and GMP in food plants but there are still many problems. I think what will help food plant to improve food safety in the future is to have a database approved by government agency where companies can share and excess information in regard of good plant design and HACCP program information in all food type. Therefore, it avoids problems caused by bad equipment design or inexperience HACCP team.
      Anyhow, great article and it provides a lot of insight in term of Listeria Monocutogenes!

    • cheryl lau 3:19 pm on December 4, 2015 Permalink | Reply

      Very interesting article! I am also surprised that this is the first time that the company has recalled their products due to Listeria monocytogenes contamination from the conditions mentioned in the FDA report. Condensed water from pipes in food manufacturing is often a problem if not dealt with. These problems usually present over time, I am surprised that the plant allowed production to continue. Perhaps the quality control personnel should ensure that the workers realize the risk involved from contamination due to irregular working conditions. The workers could then report to the supervisor when the equipment is not functioning at the optimum level to prevent these outbreaks from happening.

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