Listeria and raw milk cheese: A risk assessment involving sheep

Posted on June 13, 2016 by Douglas Powell

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.

Risk assessment of human listeriosis from semisoft cheeses made from raw sheep’s milk in Lazio and Tuscany

Roberto Condoleo, Ziad Mezher, Selene Marozzi, Antonella Guzzon, Roberto Fischetti, Matteo Senese, Stefania Sette, Luca Bucchini

Risk Analysis, June 2016, doi:10.1111/risa.12649

http://onlinelibrary.wiley.com/doi/10.1111/risa.12649/abstract;jsessionid=519D74728E4A34E1CE300B856B99D54B.f04t04

Taking it further: Quantitative microbiological risk assessment and source attribution for Salmonella

Posted on March 27, 2016 by Douglas Powell

The current issue of Risk Analysis contains several papers regarding QMRA and Salmonella.

In a recent report from the World Health Organisation, the global impact of Salmonella in 2010 was estimated to be 65–382 million illnesses and 43,000–88,000 deaths, resulting in a disease burden of 3.2–7.2 million disability-adjusted life years (DALYs).[3] Controlling Salmonella in the food chain will require intervention measures, which come at a significant cost but these should be balanced with the cost of Salmonella infections to society.[5]

Despite a wealth of published research work relating to Salmonella, many countries still struggle with identifying the best ways to prevent and control foodborne salmonellosis. Two questions are particularly important to answer in this respect: ([1]) What are the most important sources of human salmonellosis within the country? and ([2]) When a (livestock) source is identified as important, how do we best prevent and control the dissemination of Salmonella through that farm-to-consumption pathway? The articles presented in this series continue the desire to answer these questions and hence eventually contribute to the reduction in the disease burden of salmonellosis in humans.

Risk Analysis, 36: 433–436

Snary, E. L., Swart, A. N. and Hald, T.

http://onlinelibrary.wiley.com/doi/10.1111/risa.12605/abstract

Application of molecular typing results in source attribution models: the case of multiple locus variable number tandem repeat analysis (MLVA) of Salmonella isolates obtained from integrated surveillance in Denmark

Risk Analysis, 36: 571–588

de Knegt, L. V., Pires, S. M., Löfström, C., Sørensen, G., Pedersen, K., Torpdahl, M., Nielsen, E. M. and Hald, T.

http://onlinelibrary.wiley.com/doi/10.1111/risa.12483/abstract

Salmonella is an important cause of bacterial foodborne infections in Denmark. To identify the main animal-food sources of human salmonellosis, risk managers have relied on a routine application of a microbial subtyping-based source attribution model since 1995. In 2013, multiple locus variable number tandem repeat analysis (MLVA) substituted phage typing as the subtyping method for surveillance of S. Enteritidis and S. Typhimurium isolated from animals, food, and humans in Denmark.

The purpose of this study was to develop a modeling approach applying a combination of serovars, MLVA types, and antibiotic resistance profiles for the Salmonella source attribution, and assess the utility of the results for the food safety decisionmakers. Full and simplified MLVA schemes from surveillance data were tested, and model fit and consistency of results were assessed using statistical measures. We conclude that loci schemes STTR5/STTR10/STTR3 for S. Typhimurium and SE9/SE5/SE2/SE1/SE3 for S. Enteritidis can be used in microbial subtyping-based source attribution models. Based on the results, we discuss that an adjustment of the discriminatory level of the subtyping method applied often will be required to fit the purpose of the study and the available data. The issues discussed are also considered highly relevant when applying, e.g., extended multi-locus sequence typing or next-generation sequencing techniques.

Assessing the effectiveness of on-farm and abattoir interventions in reducing pig meat–borne Salmonellosis within E.U. member states

Risk Analysis, 36: 546–56

Hill, A. A., Simons, R. L., Swart, A. N., Kelly, L., Hald, T. and Snary, E. L.

http://onlinelibrary.wiley.com/doi/10.1111/risa.12568/abstract

As part of the evidence base for the development of national control plans for Salmonella spp. in pigs for E.U. Member States, a quantitative microbiological risk assessment was funded to support the scientific opinion required by the EC from the European Food Safety Authority. The main aim of the risk assessment was to assess the effectiveness of interventions implemented on-farm and at the abattoir in reducing human cases of pig meat–borne salmonellosis, and how the effects of these interventions may vary across E.U. Member States. Two case study Member States have been chosen to assess the effect of the interventions investigated. Reducing both breeding herd and slaughter pig prevalence were effective in achieving reductions in the number of expected human illnesses in both case study Member States. However, there is scarce evidence to suggest which specific on-farm interventions could achieve consistent reductions in either breeding herd or slaughter pig prevalence.

Hypothetical reductions in feed contamination rates were important in reducing slaughter pig prevalence for the case study Member State where prevalence of infection was already low, but not for the high-prevalence case study. The most significant reductions were achieved by a 1- or 2-log decrease of Salmonella contamination of the carcass post-evisceration; a 1-log decrease in average contamination produced a 90% reduction in human illness. The intervention analyses suggest that abattoir intervention may be the most effective way to reduce human exposure to Salmonella spp. However, a combined farm/abattoir approach would likely have cumulative benefits. On-farm intervention is probably most effective at the breeding-herd level for high-prevalence Member States; once infection in the breeding herd has been reduced to a low enough level, then feed and biosecurity measures would become increasingly more effective.

Toxo in meat – US edition

Posted on December 8, 2015 by Douglas Powell

Toxoplasma gondii is a global protozoan parasite capable of infecting most warm-blooded animals. Although healthy adult humans generally have no symptoms, severe illness does occur in certain groups, including congenitally infected fetuses and newborns, immunocompromised individuals including transplant patients.

Epidemiological studies have demonstrated that consumption of raw or undercooked meat products is one of the major sources of infection with T. gondii. The goal of this study was to develop a framework to qualitatively estimate the exposure risk to T. gondii from various meat products consumed in the United States.

Risk estimates of various meats were analyzed by a farm-to-retail qualitative assessment that included evaluation of farm, abattoir, storage and transportation, meat processing, packaging, and retail modules. It was found that exposure risks associated with meats from free-range chickens, nonconfinement-raised pigs, goats, and lamb are higher than those from confinement-raised pigs, cattle, and caged chickens. For fresh meat products, risk at the retail level was similar to that at the farm level unless meats had been frozen or moisture enhanced.

Our results showed that meat processing, such as salting, freezing, commercial hot air drying, long fermentation times, hot smoking, and cooking, are able to reduce T. gondii levels in meat products. whereas nitrite and/or nitrate, spice, low pH, and cold storage have no effect on the viability of T. gondii tissue cysts. Raw-fermented sausage, cured raw meat, meat that is not hot-air dried, and fresh processed meat were associated with higher exposure risks compared with cooked meat and frozen meat.

This study provides a reference for meat management control programs to determine critical control points and serves as the foundation for future quantitative risk assessments.

Qualitative assessment for Toxoplasma gondii exposure risk associated with meat products in the United States

Journal of Food Protection, Number 12, December 2015

Miao Guo, Robert L. Buchanan, Jitender P. Dubey, Dolores E. Hill, Elisabetta Lambertini, Yuqing Ying, Ray H. Gamble, Jeffrey L. Jones, and Abani K. Pradhan

http://www.ingentaconnect.com/content/iafp/jfp/2015/00000078/00000012/art00013

Chlorine is still a friend: Gastro from water wells in Canada

Posted on November 18, 2015 by Douglas Powell

Waterborne illness related to the consumption of contaminated or inadequately treated water is a global public health concern.

Although the magnitude of drinking water-related illnesses in developed countries is lower than that observed in developing regions of the world, drinking water is still responsible for a proportion of all cases of acute gastrointestinal illness (AGI) in Canada.

The estimated burden of endemic AGI in Canada is 20·5 million cases annually – this estimate accounts for under-reporting and under-diagnosis. About 4 million of these cases are domestically acquired and foodborne, yet the proportion of waterborne cases is unknown. There is evidence that individuals served by private systems and small community systems may be more at risk of waterborne illness than those served by municipal drinking water systems in Canada. However, little is known regarding the contribution of these systems to the overall drinking water-related AGI burden in Canada.

Private water supplies serve an estimated 12% of the Canadian population, or ~4·1 million people. An estimated 1·4 million (4·1%) people in Canada are served by small groundwater (2·6%) and surface water (1·5%) supplies. The objective of this research is to estimate the number of AGI cases attributable to water consumption from these supplies in Canada using a quantitative microbial risk assessment (QMRA) approach. This provides a framework for others to develop burden of waterborne illness estimates for small water supplies. A multi-pathogen QMRA of Giardia, Cryptosporidium, Campylobacter, E. coli O157 and norovirus, chosen as index waterborne pathogens, for various source water and treatment combinations was performed. It is estimated that 103 230 AGI cases per year are due to the presence of these five pathogens in drinking water from private and small community water systems in Canada.

In addition to providing a mechanism to assess the potential burden of AGI attributed to small systems and private well water in Canada, this research supports the use of QMRA as an effective source attribution tool when there is a lack of randomized controlled trial data to evaluate the public health risk of an exposure source. QMRA is also a powerful tool for identifying existing knowledge gaps on the national scale to inform future surveillance and research efforts.

Estimating the burden of acute gastrointestinal illness due to Giardia, Cryptosporidium, Campylobacter, E. coli O157 and norovirus associated with private wells and small water systems in Canada

Epidemiology and Infection, August 2015, pages 1-16, DOI: 10.1017/S0950268815002071

H.M. Murphy, M.K. Thomas, P.J. Schmidt, D.T. Medeiros, S. McFadyen, and K.D.M. Pintar

http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=10034786&fulltextType=RA&fileId=S0950268815002071

Listeria uses alternative metabolic pathways to grow on cold salmon

Posted on August 6, 2015 by Douglas Powell

Listeria monocytogenes grows on refrigerated smoked salmon by way of different metabolic pathways from those it uses when growing on laboratory media. This discovery could lead to reduced incidences of foodborne illness and death, said principal investigator Teresa Bergholz. The research appeared in Applied and Environmental Microbiology, a journal of the American Society for Microbiology.

In the study, the investigators showed that L. monocytogenes grows on cold smoked salmon by using different metabolic pathways to obtain energy from those it uses on laboratory media, even when the media was modified to have the same salt content and pH as the salmon. To grow on the salmon, the bacterium upregulates genes that enable it to use two compounds from cell membranes — ethanolamine and propanediol — as energy sources.

L. monocytogenes, as well as Salmonella, are known to use those same genes to grow within a host — in the gastrointestinal tract, and on macrophages. “There may be ways we can use this information to control the pathogen both in foods as well as in infected people,” said Bergholz, assistant professor in the Department of Veterinary and Microbiological Sciences at North Dakota State University, Fargo. “Understanding how a foodborne pathogen adapts to environmental stresses it encounters on a specific food could allow food microbiologists to develop inhibitors of metabolic or stress response pathways that are necessary for the pathogen to grow or survive on that product.”

“The information may also enable improved risk assessments, as virulence of a pathogen may be affected considerably by the stress responses and/or metabolic pathways used to survive on the food,” said Bergholz.

Bergholz noted that ready to eat products typically have very low levels of contamination with L. monocytogenes, and that the bacterium must be able to grow on the product during refrigerated storage in order to reach an infectious dose. “In many cases, the addition of organic acids will slow or stop the growth of this pathogen on ready to eat meats and seafood.”

I volunteer: Study on THC in animal products

Posted on June 26, 2015 by Douglas Powell

The European Food Safety Authority (EFSA) was asked to deliver a scientific opinion on the risks for human health related to the presence of tetrahydrocannabinol (THC) in milk and other food of animal origin.

THC, more precisely delta-9-tetrahydrocannabinol (Δ9-THC) is derived from the hemp plant Cannabis sativa. In fresh plant material, up to 90 % of total Δ9-THC is present as the non-psychoactive precursor Δ9-THC acid. Since few data on Δ9-THC levels in foods of animal origin were available, the Panel on Contaminants in the Food Chain (CONTAM Panel) estimated acute human dietary exposure to Δ9-THC combining different scenarios for the presence of Δ9-THC in hemp seed-derived feed materials.

Acute exposure to Δ9-THC from the consumption of milk and dairy products ranged between 0.001 and 0.03 µg/kg body weight (b.w.) per day in adults, and 0.006 and 0.13 µg/kg b.w. per day in toddlers. From human data, the CONTAM Panel concluded that 2.5 mg Δ9-THC/day, corresponding to 0.036 mg Δ9-THC/kg b.w. per day, represents the lowest observed adverse effect level. By applying an overall uncertainty factor of 30, an acute reference dose (ARfD) of 1 μg Δ9-THC/kg b.w. was derived. The exposure estimates are at most 3 % and 13 % the ARfD, in adults and toddlers, respectively.

The CONTAM Panel concluded that exposure to Δ9-THC via consumption of milk and dairy products, resulting from the use of hemp seed-derived feed materials at the reported concentrations, is unlikely to pose a health concern.

A risk assessment resulting from the use of whole hemp plant-derived feed materials is currently not feasible due to a lack of occurrence data. The CONTAM Panel could also not conclude on the possible risks to public health from exposure to Δ9-THC via consumption of animal tissues and eggs, due to a lack of data on the potential transfer and fate of Δ9-THC.

Scientific Opinion on the risks for human health related to the presence of tetrahydrocannabinol (THC) in milk and other food of animal origin

EFSA Journal 2015;13(6):4141[125 pp.]

EFSA

http://www.efsa.europa.eu/en/efsajournal/pub/4141.htm?utm_source=feed&utm_medium=rss&utm_campaign=ej

Food safety nerd alert: FDA launches iRISK 2.0

Posted on February 27, 2015 by Douglas Powell

The U.S. Food and Drug Administration has released FDA-iRISK 2.0, an enhanced version of the free web-based tool that helps users conduct their own quantitative risk assessments in support of food safety. The Joint Institute for Food Safety and Applied Nutrition, (JIFSAN) will also host a webinar to highlight key features of FDA-iRISK 2.0.

FDA-iRISK 2.0 allows users to rank and compare risks and predict the effectiveness of prevention and control measures. Enhanced features include:

advanced modeling methods, such as rare events and new dose-response modeling options;

faster development of alternative scenarios;

innovative reporting of results;

graphical representations of dose-response and variability in contamination and consumption to better understand and verify data; and

easier data-sharing with other users.

The JIFSAN webinar is scheduled for March 11, 2015 from 11:00 am to 12:00 pm EDT. The webinar is free, but registration is required. To register, please visit JIFSAN Event Registration.

I was called Boog in high school — after baseball great, Miller Lite pitchman and mesquite BBQ connoisseur, Boog Powell — but never Booger.

You’ll have to go here to see the video from Revenge of the Nerds.

Salmonella and raw leafy greens most dangerous according to EU risk assessment model

Posted on January 28, 2015 by Douglas Powell

Foods of non-animal origin (FoNAO) are consumed in a variety of forms, being a major component of almost all meals. These food types have the potential to be associated with large outbreaks as seen in 2011 associated with VTEC O104.

In order to identify and rank specific food/pathogen combinations most often linked to human cases originating from FoNAO in the EU, a semi-quantitative model was developed using seven criteria: strength of associations between food and pathogen based on the foodborne outbreak data from EU Zoonoses Monitoring (2007–2011), incidence of illness, burden of disease, dose–response relationship, consumption, prevalence of contamination and pathogen growth potential during shelf life.

The top ranking food/pathogen combination was Salmonella spp. and leafy greens eaten raw followed by (in equal rank) Salmonella spp. and bulb and stem vegetables, Salmonella spp. and tomatoes, Salmonella spp. and melons, and pathogenic Escherichia coli and fresh pods, legumes or grains.

Despite the inherent assumptions and limitations, this risk model is considered a tool for risk managers, as it allows ranking of food/pathogen combinations most often linked to foodborne human cases originating from FoNAO in the EU. Efforts to collect additional data even in the absence of reported outbreaks as well as to enhance the quality of the EU-specific data, which was used as input for all the model criteria, will allow the improvement of the model outputs. Furthermore, it is recommended that harmonised terminology be applied to the categorisation of foods collected for different reasons, e.g. monitoring, surveillance, outbreak investigation and consumption. In addition, to assist future microbiological risk assessments, consideration should be given to the collection of additional information on how food has been processed, stored and prepared as part of the above data collection exercises.

Risk ranking of pathogens in ready-to-eat unprocessed foods of non-animal origin (FoNAO) in the EU: Initial evaluation using outbreak data (2007–2011)

International Journal of Food Microbiology, Volume 195, 16 February 2015, Pages 9–19

M.T. Da Silva Felício a, , , T. Hald b, E. Liebana a A. Allende c, M. Hugas a, C. Nguyen-The d, e, G. Skoien Johannessen f, T. Niskanen g, M. Uyttendaeleh, J. McLauchlin

http://www.sciencedirect.com/science/article/pii/S0168160514005443

Salmonella and listeria and raw milk

Posted on January 9, 2015 by Douglas Powell

Two quantitative risk assessment (RA) models were developed to describe the risk of salmonellosis and listeriosis linked to consumption of raw milk sold in vending machines in Italy.

Exposure assessment considered the official microbiological records monitoring raw milk samples from vending machines performed by the regional veterinary authorities from 2008 to 2011, microbial growth during storage, destruction experiments, consumption frequency of raw milk, serving size, and consumption preference.

Two separate RA models were developed: one for the consumption of boiled milk and the other for the consumption of raw milk. The RA models predicted no human listeriosis cases per year either in the best or worst storage conditions and with or without boiling raw milk, whereas the annual estimated cases of salmonellosis depend on the dose-response relationships used in the model, the milk storage conditions, and consumer behavior in relation to boiling raw milk or not.

For example, the estimated salmonellosis cases ranged from no expected cases, assuming that the entire population boiled milk before consumption, to a maximum of 980,128 cases, assuming that the entire population drank raw milk without boiling, in the worst milk storage conditions, and with the lowest dose-response model.

The findings of this study clearly show how consumer behavior could affect the probability and number of salmonellosis cases and in general, the risk of illness. Hence, the proposed RA models emphasize yet again that boiling milk before drinking is a simple yet effective tool to protect consumers against the risk of illness inherent in the consumption of raw milk.

The models may also offer risk managers a useful tool to identify or implement appropriate measures to control the risk of acquiring foodborne pathogens. Quantification of the risks associated with raw milk consumption is necessary from a public health perspective.

Quantitative risk assessment of human salmonellosis and listeriosis related to the consumption of raw milk in Italy

Journal of Food Protection®, Number 1, January 2015, pp. 4-234, pp. 13-21(9)

Giacometti, Federica; Bonilauri, Paolo; Albonetti, Sabrina; Amatiste, Simonetta; Arrigoni, Norma; Bianchi, Manila; Bertasi, Barbara; Bilei, Stefano; Bolzoni, Giuseppe; Cascone, Giuseppe; Comin, Damiano; Daminelli, Paolo; Decastelli, Lucia; Merialdi, Giuseppe; Mioni, Renzo; Peli, Angelo; Petruzzelli, Annalisa; Tonucci, Franco; Bonerba, Elisabetta; Serraino, Andrea

http://www.ingentaconnect.com/content/iafp/jfp/2015/00000078/00000001/art00004

Listeriosis: Bad food, bad holding, susceptible population

Posted on January 9, 2015 by Douglas Powell

The Interagency Risk Assessment—Listeria monocytogenes (Lm) in Retail Delicatessens provides a scientific assessment of the risk of listeriosis associated with the consumption of ready-to-eat (RTE) foods commonly prepared and sold in the delicatessen (deli) of a retail food store.

The quantitative risk assessment (QRA) model simulates the behavior of retail employees in a deli department and tracks the Lm potentially present in this environment and in the food. Bacterial growth, bacterial inactivation (following washing and sanitizing actions), and cross-contamination (from object to object, from food to object, or from object to food) are evaluated through a discrete event modeling approach. The QRA evaluates the risk per serving of deli-prepared RTE food for the susceptible and general population, using a dose-response model from the literature.

This QRA considers six separate retail baseline conditions and provides information on the predicted risk of listeriosis for each. Among the baseline conditions considered, the model predicts that (i) retail delis without an environmental source of Lm (such as niches), retail delis without niches that do apply temperature control, and retail delis with niches that do apply temperature control lead to lower predicted risk of listeriosis relative to retail delis with niches and (ii) retail delis with incoming RTE foods that are contaminated with Lm lead to higher predicted risk of listeriosis, directly or through cross-contamination, whether the contaminated incoming product supports growth or not.

The risk assessment predicts that listeriosis cases associated with retail delicatessens result from a sequence of key events: (i) the contaminated RTE food supports Lm growth; (ii) improper retail and/or consumer storage temperature or handling results in the growth of Lm on the RTE food; and (iii) the consumer of this RTE food is susceptible to listeriosis. The risk assessment model, therefore, predicts that cross-contamination with Lm at retail predominantly results in sporadic cases.

Journal of Food Protection®, Number 1, January 2015, pp. 4-234, pp. 134-145(12)

Pouillot, Régis; Gallagher, Daniel; Tang, Jia; Hoelzer, Karin; Kause, Janell; Dennis, Sherri B.

http://www.ingentaconnect.com/content/iafp/jfp/2015/00000078/00000001/art00019

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