Risk Of Listeriosis Research Articles

Quantification of temperature fluctuations in restaurant coolers and modelled Listeria monocytogenes growth


 Background: Coolers in food service establishments should ideally operate at 4°C or less. However in restaurant environments cooler doors are continually being opened and closed as food workers gather and store items. These actions may lead to temperature fluctuations in coolers which may pose a health risk towards the storage of potentially hazardous foods. This study measured and analyzed temperature fluctuations in coolers and quantified the risk they presented by modelling Listeria monocytogenes growth in response to these temperatures. Method: ACR Systems Inc. Smart Buttons were placed near the opening of restaurant coolers and recorded temperatures over a 1-week span. Food Spoilage and Safety Predictor (FSSP) was used to model L. monocytogenes growth in response to the collected cooler temperatures. Results: Coolers spend significantly less than 50% of the time above 4°C. The magnitude of temperature fluctuations during open business hours was found to be insignificant in comparison to fluctuations during closed business hours. However, fluctuations were significantly greater in reach-in coolers than in walk-in coolers. With respect to modeled L. monocytogenes growth, it was inconclusive on whether growth would be more or less than Health Canada’s 100cfu/g policy in smoked salmon. However growth was significantly less than this limit in ready-to-eat ham. Conclusions: More restaurant coolers need to be analyzed to confirm whether the defrost cycles of coolers have a greater impact on temperature fluctuations above 4°C than the daily activities of staff members. In addition, more coolers need to be analyzed to determine whether L. monocytogenes growth in smoked salmon stored in coolers for a week grow significantly more than 100cfu/g. However, it can be concluded L. monocytogenes growth will be significantly less than 100cfu/g in ready-to-eat ham and will pose a lower risk for listeriosis than smoked salmon.

Industrial Applications of Selected JFS Articles

Industrial Applications of Selected <i>JFS</i> Articles

Pregnancy-related listeriosis.

About one in seven cases of listeriosis occurs in pregnant women, and, although listeriosis is rare, it is the third leading cause of death from food-borne infections. Pregnancy-related listeriosis increases the risk for fetal and neonatal mortality by approximately 21%. During pregnancy, infections are more likely to occur in the third trimester (66%) than the first trimester (3%). However, fetal and neonatal adverse effects are less common as gestational age increases or with older gestational age at birth. Pregnant women seem highly susceptible in some listeriosis outbreaks making up a large percentage of cases, whereas others contain very few. Whether this results from differences in strains of L. monocytogenes, exposures, or other factors remains to be determined. Food and Agriculture Organization of United Nations/World Health Organization (FAO/WHO) estimates the human lethal dose for 50% (LD50 ) for fetal/neonatal loss is 1.9 × 106 colony forming units (CFUs) L. monocytogenes. Animal models have been developed for pregnancy-related listeriosis showing similar susceptibility and clinical outcomes as in humans. Nonhuman primate and guinea pig animal models have similar (LD50 ) values to the estimated human LD50 . Additional animal studies are needed to understand the pathways leading to fetal and neonatal listeriosis in humans. More information is needed to understand dose response, to model risk for listeriosis at lower concentrations, and to determine why some pregnant women may be more susceptible than others. To better treat listeriosis during pregnancy, biomarkers for early diagnosis of listeriosis are also needed. Last, pregnant women need to be educated about avoiding high-risk foods, like Mexican-style cheese and ready-to-eat meats. Birth Defects Research 109:324-335, 2017.© 2017 Wiley Periodicals, Inc.

Effect of intervention strategies on the risk of infection from Listeria monocytogenes due to consumption of fresh baby spinach leaves: A quantitative approach

The purpose of this study was to conduct a quantitative microbial risk assessment (QMRA) for Listeria monocytogenes infection from consumption of fresh baby spinach leaves, and provide recommendations on intervention strategies including water washing, use of sanitizers (peracetic acid (PAA), chlorine dioxide (ClO2) and chlorine), irradiation, and irradiation-Modified Atmosphere Packaging (MAP) combinations, based on different scenarios. The food chain of fresh baby spinach from processing facility up to consumption was simulated employing @Risk software. The QMRA models predict that the mean annual number of L. monocytogenes infection cases per year for the U.S. population due to consumption of spinach leaves ranged from 115 to 536 cases – meaning that the incidence of L. monocytogenes infection ranged from 1.2 to 5.5 cases per hundred thousand people. Findings strongly encourage the application of irradiation combined with MAP since this intervention strategy reduced the mean risk of listeriosis per random serving by 65.6%. The results of this study suggest that intervention methods could reduce the concentration of L. monocytogenes on spinach leaves under the detectable limit (0.04 CFU g-1) at the processing facility, though this pathogen could reach unacceptable levels at the time of consumption.

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?

In this study, we investigated 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). Samples were stored at recommended maximum refrigerator temperature (8°C in Sweden) or at an abuse temperature (15°C) for up to 7 days. Mixed-ingredient salad supported considerable growth when stored at 15°C during shelf life (3 days), with populations of L. monocytogenes , pathogenic Y. enterocolitica , and E. coli O157:H7 gfp+ increasing from less than 2.0 log CFU/g on day 0 to 7.0, 4.0, and 5.6 log CFU/g, respectively. However, 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. 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. To explore the food safety implications of these findings, bacterial numbers were translated into risks of infection by modeling. 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. This indicates that efforts should focus on preventing temperature abuse during storage to mitigate the risk of listeriosis. The storage conditions recommended for mixed-ingredient salads in Sweden (maximum 8°C for 3 days) did not prevent growth of L. monocytogenes in baby spinach mixed with chicken meat. Manufacturers preparing these salads should be aware of this, and recommended storage temperature should be revised downwards to reduce the risk of foodborne disease.

Risk of listeriosis with proton pump inhibitors

Risk of listeriosis with proton pump inhibitors

Use of proton pump inhibitors and the risk of listeriosis. A nationwide registry-based case-control study

Recent studies suggest that proton pump inhibitors (PPIs) may increase the risk for listeriosis. We investigated a potential association in cases of nonpregnancy-associated listeriosis using registry data. We conducted a population-based, case-control study using Danish health registries. Cases (n = 721) were defined as patients aged ≥45 years notified with listeriosis from July 1994 to December 2012. We selected 34800 controls using risk-set sampling. Controls were individually matched for age, sex, and municipality. Data on use of PPIs and other drugs and hospitalization diagnoses over a 5-year period were extracted from nationwide health registries. A comorbidity index (CMI) was constructed. We calculated the association between use of PPIs and related drugs within 30 days (current use) and other time windows before the index date. Using conditional logistic regression, matched odds ratios (ORs) adjusted for CMI and confounders were estimated. The adjusted OR for current use of PPIs and development of listeriosis was 2.81 (95% confidence interval [CI], 2.14-3.69). PPI usage up to 90 days before the index date remained statistically significant. Subgroup analyses revealed increasing ORs with decreasing age and level of comorbidity and an increased OR for concurrent glucocorticoid treatment (OR, 4.61; 95% CI, 3.01-7.06). No significant association was found for current use of histamine-2-receptor antagonists (adjusted OR, 1.82; 95% CI, 0.89-3.71). Prescribed PPIs were associated with increased risk of listeriosis. The risk waned with time since last prescription redemption. PPIs may have unwanted side effects in vulnerable populations.

How older people store and use food could increase listeriosis risk.

People with weakened immunity, including older adults, are known to be at increased risk of foodborne disease, in particular, listeriosis. Listeriosis is associated with the highest levels of hospitalisation and mortality of all foodborne pathogens in the UK.

Silage and livestock health

Silage making involves preserving forage crops by fermentation of water-soluble carbohydrates (sugars) to organic acids. The fermentation is relatively uncontrolled and inadequate acidification can allow the growth of undesirable microorganisms such as enterobacteria and clostridia. Ingress of oxygen to the outer layer of the silo or bale during the storage period encourages growth of yeasts and moulds. Mycobacterium bovis may survive in silages with pH above 5.0. Outgrowth of clostridia in aerobically deteriorating silage can lead to high counts of butyric acid spores in silage that can contaminate milk and cheese. Milk may be contaminated with Penicillium toxins and be rejected for containing antibiotics. Specific disease risks to livestock from poorly preserved silage include bacterial endotoxicosis, listeriosis, botulism, mycotoxicosis and nitric acid poisoning in addition to reduced feed value. Rapid acidification is essential once the crop is ensiled to restrict the growth of enterobacteria, listeria and clostridia. Oxygen barrier film, in addition to reducing loss of dry matter during the storage period, prevents clostridial outgrowth in the outer layer of the silo and is also likely to reduce the risk of listeriosis.

Listeria monocytogenes in Retail Delicatessens: An Interagency Risk Assessment—Risk Mitigations

Cross-contamination, improper holding temperatures, and insufficient sanitary practices are known retail practices that may lead to product contamination and growth of Listeria monocytogenes. However, the relative importance of control options to mitigate the risk of invasive listeriosis from ready-to-eat (RTE) products sliced or prepared at retail is not well understood. This study illustrates the utility of a quantitative risk assessment model described in a first article of this series (Pouillot, R., D. Gallagher, J. Tang, K. Hoelzer, J. Kause, and S. B. Dennis, J. Food Prot. 78:134-145, 2015) to evaluate the public health impact associated with changes in retail deli practices and interventions. Twenty-two mitigation scenarios were modeled and evaluated under six different baseline conditions. These scenarios were related to sanitation, worker behavior, use of growth inhibitors, cross-contamination, storage temperature control, and reduction of the level of L. monocytogenes on incoming RTE food products. The mean risk per serving of RTE products obtained under these scenarios was then compared with the risk estimated in the baseline condition. Some risk mitigations had a consistent impact on the predicted listeriosis risk in all baseline conditions (e.g. presence or absence of growth inhibitor), whereas others were greatly dependent on the initial baseline conditions or practices in the deli (e.g. preslicing of products). Overall, the control of the bacterial growth and the control of contamination at its source were major factors of listeriosis risk in these settings. Although control of cross-contamination and continued sanitation were also important, the decrease in the predicted risk was not amenable to a simple solution. Findings from these predictive scenario analyses are intended to encourage improvements to retail food safety practices and mitigation strategies to control L. monocytogenes in RTE foods more effectively and to demonstrate the utility of quantitative risk assessment models to inform risk management decisions.

Older adults' domestic kitchen practices associated with an increased risk of listeriosis.

This article was published in Perspectives in Public Health on 1 July 2016, available at http://dx.doi.org/10.1177/1757913916649818

Risk Assessment of Human Listeriosis from Semisoft Cheeses Made from Raw Sheep's Milk in Lazio and Tuscany (Italy).

Semisoft cheese made from raw sheep's milk is traditionally and economically important in southern Europe. However, raw milk cheese is also a known vehicle of human listeriosis and contamination of sheep cheese with Listeria monocytogenes has been reported. In the present study, we have developed and applied a quantitative risk assessment model, based on available evidence and challenge testing, to estimate risk of invasive listeriosis due to consumption of an artisanal sheep cheese made with raw milk collected from a single flock in central Italy. In the model, contamination of milk may originate from the farm environment or from mastitic animals, with potential growth of the pathogen in bulk milk and during cheese ripening. Based on the 48-day challenge test of a local semisoft raw sheep's milk cheese we found limited growth only during the initial phase of ripening (24 hours) and no growth or limited decline during the following ripening period. In our simulation, in the baseline scenario, 2.2% of cheese servings are estimated to have at least 1 colony forming unit (CFU) per gram. Of these, 15.1% would be above the current E.U. limit of 100 CFU/g (5.2% would exceed 1,000 CFU/g). Risk of invasive listeriosis per random serving is estimated in the 10-12 range (mean) for healthy adults, and in the 10-10 range (mean) for vulnerable populations. When small flocks (10-36 animals) are combined with the presence of a sheep with undetected subclinical mastitis, risk of listeriosis increases and such flocks may represent a public health risk.

Study progress of listeria mononucleosis in children

Listeria disease(LD) is a zoonosis, caused by Listeria monocytogenes(LM), the main route of transmission is foodborne spread, can cause outbreak.Pregnant women and their fetuses or neonates, older adults, and persons with underlying conditions that impair cell-mediated immunity are at a particularly high risk of invasive liste-riosis.The gastroenteritis, meningitis and bacteremia are the common clinical feature.LD in children is rare.It can cause the neonates sepsis and central nervous system infection.Because of the natural resistance to cephalosporins, the choice of antibiotics seemd more important.By this article, LM in children and benefit for clinical work was recognized. Key words: Child; Listeria mononucleosis; Listeria disease

Prevalence of Listeria Spp. and Listeria Monocytogenes in Cattle Farms in Cyprus using Bulk Tank Milk Samples

AbstractListeria monocytogenes is an important foodborne pathogen which causes listeriosis in humans and animals. Presence of Listeria spp. and L. monocytogenes in raw bovine milk could lead to the manufacture of contaminated products due to lack or insufficient pasteurization or cross‐contamination. The purpose of this study was to record the prevalence of Listeria spp. and L. monocytogenes in all the Cypriot dairy farms, using bulk tank milk (BTM) samples. A total of 205 raw BTM samples were analyzed for Listeria spp. and L. monocytogenes. In addition a total viable count (TVC) was also performed in parallel in an attempt to correlate high TVC with the presence of Listeria. Results revealed a total of three samples (1.46%; 95% CI: 0.3–4.4%) positive for Listeria spp. two (0.98%; 95% CI: 0.04–3.72%), of which were successfully identified as L. monocytogenes. Molecular serotyping indicated that the two isolates were both 1/2a. This is the first report in Cyprus documenting the prevalence of Listeria spp. and L. monocytogenes in the raw BTM of all Cypriot dairy farms revealing a low prevalence in a reported asymptomatic population. Monitoring the prevalence is essential in an attempt to protect animal health and welfare as well as human health by reducing the risk of listeriosis through consumption of milk and dairy products.Practical ApplicationsThere is an increasing need to better understand the prevalence of Listeria monocytogenes in the environment and food, given the rise of listeriosis in Europe, as reported by EFSA. Raw milk is an important exposure vehicle to humans either directly, through the consumption of unpasteurized products, or as a result of cross‐contamination in food establishments. Previous detection studies have been published in Europe and throughout the world but never before a full prevalence study which records the results in bulk tank milk (BTM) following the sampling from all dairy herds in a country. In addition, this is the first report in Cyprus documenting the prevalence of L. monocytogenes in raw BTM, revealing a low prevalence in a reported asymptomatic population of cattle. Furthermore, the predominant serotypes are identified, providing useful epidemiological information for future studies in Cyprus and throughout the world.

Outbreaks of listeriosis associated with deli meats and cheese: an overview

Microbial pollution of foods by undesirable microorganisms is a global food safety issue. One of such undesirable microorganism is the psychrotrophic, pathogenic specie of Listeria—Listeria <em>monocytogenes </em>that survives at low temperature. The source of contamination of this microbe into foods can be many including the food processing facilities due to improper sanitation procedures. The review of the literature on this important topic shows there are increasing concerns as regards contamination from Listeria in foods leading to many cases of listeriosis disease and food recalls. Ready-to-eat products, such as delicatessen (deli) meats and soft cheeses have repeatedly been identified by foodborne disease control programs as sources of outbreaks and products that put humans at risk for listeriosis. Although, most listeriosis cases tend to be sporadic in occurrence, outbreaks do occur frequently. Due to the global phenomenon of outbreaks associated with Listeria in deli meats and cheese, it requires an urgent attention from national and international authorities through rigorous procedures for its identification, surveillance procedures that can bring more awareness to the general public. There is also a need for more reports on the cases of Listeria particularly in developing countries, the standardization of identification procedures, and an improvement on national control programs by adequate surveillance.

Consumers’ behavior in quantitative microbial risk assessment for pathogens in raw milk: Incorporation of the likelihood of consumption as a function of storage time and temperature

Foodborne disease as a result of raw milk consumption is an increasing concern in Western countries. Quantitative microbial risk assessment models have been used to estimate the risk of illness due to different pathogens in raw milk. In these models, the duration and temperature of storage before consumption have a critical influence in the final outcome of the simulations and are usually described and modeled as independent distributions in the consumer phase module. We hypothesize that this assumption can result in the computation, during simulations, of extreme scenarios that ultimately lead to an overestimation of the risk. In this study, a sensorial analysis was conducted to replicate consumers’ behavior. The results of the analysis were used to establish, by means of a logistic model, the relationship between time–temperature combinations and the probability that a serving of raw milk is actually consumed. To assess our hypothesis, 2 recently published quantitative microbial risk assessment models quantifying the risks of listeriosis and salmonellosis related to the consumption of raw milk were implemented. First, the default settings described in the publications were kept; second, the likelihood of consumption as a function of the length and temperature of storage was included. When results were compared, the density of computed extreme scenarios decreased significantly in the modified model; consequently, the probability of illness and the expected number of cases per year also decreased. Reductions of 11.6 and 12.7% in the proportion of computed scenarios in which a contaminated milk serving was consumed were observed for the first and the second study, respectively. Our results confirm that overlooking the time–temperature dependency may yield to an important overestimation of the risk. Furthermore, we provide estimates of this dependency that could easily be implemented in future quantitative microbial risk assessment models of raw milk pathogens.

Listeria monocytogenes infection in a 56-year-old female cancer patient: a case report

Introduction: Listeria monocytogenes, the aetiological agent of foodborne listeriosis, can cause a severe and potentially fatal foodborne infection. Listeriosis is associated with acquired immunodeficiency or the underlying immunosuppression found in pregnant women, cancer patients and the elderly. Listeriosis emerged in developed countries in the early 1980s with the emergence of human immunodeficiency virus/AIDS and the popularity of minimally processed foods; however, few cases have been reported from developing countries. Here, we present a successfully treated case of listeriosis in a patient undergoing chemotherapy. Case presentation: An elderly female patient with thyroid carcinoma metastasized to the lungs became seriously ill following the initiation of chemotherapy. The patient was admitted with symptoms of generalized convulsion and an altered level of consciousness and was treated empirically with meropenem, amikacin and linezolid injection. Cultures of blood and cerebrospinal fluid revealed Listeria monocytogenes on day 5 post-admission. The patient was treated with ampicillin (2 g intravenously every 4 h), which resolved the bacterial infection by day 9. To the best of our knowledge, this is the first diagnosed and successfully treated case of listeriosis in a cancer patient to be reported from Bangladesh. Conclusion: Early diagnosis is critical for successful treatment of listeriosis. We recommend raising awareness among healthcare professionals about the diagnosis and treatment of this potentially fatal disease. Patients undergoing immunosuppressive treatments that elevate the risk of listeriosis should be monitored, and the medical histories of patients presenting with possible listeriosis should be carefully reviewed for immunosuppression. The incidence of listeriosis should be established to identify susceptible populations and to implement food safety procedures in this rapidly developing country.

Prevalence, Antimicrobial Resistance and Serotype Distribution of Listeria monocytogenes Isolated from Raw Milk and Dairy Products

AbstractThe objectives of study were to assess presence of Listeria monocytogenes, perform serotyping and investigate antibiotic resistance in raw milk and dairy products. A total of 210 milk and dairy products including white (n = 20) and kashar cheese (n = 20), ice cream (n = 20), butter (n = 20), cokelek (n = 10), kuymak (n = 10) and farm cheese (n = 10) were obtained from Samsun, Turkey. All samples were analyzed using an immunomagnetic separation‐based culture technique and strains of L. monocytogenes were confirmed by presence of hlyA and iap genes by polymerase chain reaction (PCR). L. monocytogenes was identified in 5 of 100 (5%) milk samples, serotyped as 4b and 1/2b, and in 9 of 110 (8.2%) dairy products, serotyped as 1/2a, 1/2b and 1/2c. However, L. monocytogenes was not identified from butter, kashar and ice cream samples. The antibiotic susceptibility against ampicillin, amoxicillin/clavulanic acid, erythromycin, chloramphenicol, penicillin G, oxytetracycline, tetracycline and vancomycin was assessed by disc diffusion method. It was found that 15.3% of isolates were resistant to at least one drug and 36.5% were multidrug resistant. Among isolates, resistance to tetracycline was most commonly encountered (34.6%), followed by resistance to chloramphenicol (25%) and penicillin G (23%). In conclusion, our data also indicate that consuming raw and unpasteurised milk and dairy products could pose a risk of listeriosis in humans.Practical ApplicationsAlthough there are plenty of studies about the incidence of L. monocytogenes in raw milk and dairy products in Turkey, our study is the first one in Samsun (Middle Black Sea) Region about Listeria in milk and dairy products. Also in our study, we characterized some virulence genes and serotype distribution of L. monocytogenes by PCR. Finally, we performed antibiotic resistance tests of isolates to see possible public health threats because of using overabundant antibiotics. If we analyze all these work to see the potential risk assessments in this region, our study could be a leading study in near future.

Bacteriophage cocktail significantly reduces or eliminates Listeria monocytogenes contamination on lettuce, apples, cheese, smoked salmon and frozen foods

ListShield™, a commercially available bacteriophage cocktail that specifically targets Listeria monocytogenes, was evaluated as a bio-control agent for L. monocytogenes in various Ready-To-Eat foods. ListShield™ treatment of experimentally contaminated lettuce, cheese, smoked salmon, and frozen entrèes significantly reduced (p < 0.05) L. monocytogenes contamination by 91% (1.1 log), 82% (0.7 log), 90% (1.0 log), and 99% (2.2 log), respectively. ListShield™ application, alone or combined with an antioxidant/anti-browning solution, resulted in a statistically significant (p < 0.001) 93% (1.1 log) reduction of L. monocytogenes contamination on apple slices after 24 h at 4 °C. Treatment of smoked salmon from a commercial processing facility with ListShield™ eliminated L. monocytogenes (no detectable L. monocytogenes) in both the naturally contaminated and experimentally contaminated salmon fillets. The organoleptic quality of foods was not affected by application of ListShield™, as no differences in the color, taste, or appearance were detectable. Bio-control of L. monocytogenes with lytic bacteriophage preparations such as ListShield™ can offer an environmentally-friendly, green approach for reducing the risk of listeriosis associated with the consumption of various foods that may be contaminated with L. monocytogenes.

Analysis of Older Adults’ Domestic Kitchen Storage Practices in the United Kingdom: Identification of Risk Factors Associated with Listeriosis

Increased listeriosis incidence among older adults (≥60 years) has been reported internationally, with many cases reported to be sporadic and associated with ready-to-eat (RTE) food products with extended refrigerated shelf life. Given that the home kitchen is recognized as a significant location where foodborne illnesses are acquired, it is important that consumers implement safe food practices to minimize risks. This is crucial for vulnerable consumers, such as older adults. Consumer food safety recommendations in the United Kingdom to reduce the risk of listeriosis at home include (i) following “use-by” dates on unopened prepacked RTE food products, (ii) consuming RTE food products within 2 days of opening, and (iii) ensuring the safe operating temperatures of domestic refrigerators (≤5°C). This study utilized observation, self-reporting, and microbiological analysis to determine actual food storage practices to identify behavioral risk factors. A domestic kitchen survey was conducted in older adult (≥60 years) consumers’ domestic kitchens (n = 100) in South Wales, United Kingdom. Forty-one percent of foods in home refrigerators were beyond the use-by date, of which 11% were unopened RTE food products commonly associated with listeriosis. Sixty-six percent of opened RTE foods had been or were intended to be stored beyond the recommended 2 days after opening. Older adults failed to ensure safe refrigeration temperatures, with 50% of central storage and 85% of door storage areas operating at temperatures >5°C. Older refrigerators operated at significantly (P < 0.05) higher temperatures. Given that Listeria monocytogenes was isolated in 2% of kitchens, these findings suggest that storage malpractices may have a greater effect on the potential risk of listeriosis than its presence alone. The study has determined that many older adults fail to adhere to recommendations and subject RTE foods associated with L. monocytogenes to prolonged storage at unsafe temperatures which may render food unsafe for consumption.