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Since the publication of the 2004 risk assessment, outbreaks of illness and resultant deaths due to L. monocytogenes continue to occur across the globe. Continued effort is needed to summarize and critically evaluate the most recent information on L. monocytogenes in RTE foods. New data to improve and further inform the 2004 Risk Assessment is available for nearly every factor considered previously, including new quantitative data on L. monocytogenes contamination of foods.To facilitate this work, an FAO/WHO expert meeting was held by virtual means from 20 October to 6 November 2020 to review and discuss the available data and background documents, and to assess the need to modify and update risk assessment models/tools. This report focuses on the deliberations and conclusions of the expert meeting.

Spices and dried aromatic herbs impart flavour when added to food, and they may include many parts of the plant, including berries, flowers, leaves, roots and seeds. A number of different pathogens have been found in spices on the market, especially Salmonella spp., B. cereus and C. perfringens. There have also been several disease outbreaks associated with spices and dried aromatic herbs. An increased concern and attention to the safety of spices and dried aromatic herbs prompted, the Codex Committee on Food Hygiene (CCFH) to request FAO and WHO to undertake a risk assessment on microbiological hazards in these food commodities.An expert meeting of the FAO/WHO Joint Expert Meeting on Microbiological Risk Assessment (JEMRA) considered the global evidence on the burden of illness, prevalence and concentration of selected microbial hazards with respect to various spices and dried aromatic herbs, and interventions aimed at controlling them in these commodities. The experts developed the approach to rank the health risks related to the commodity-pathogen combinations, and assessed the performance of the existing Codex sampling plan for Salmonella against several contamination scenarios.

It is well-established that Extended-spectrum beta-lactamase-producing (ESBL-) Escherichia coli challenge reliable detection of campylobacters during enrichment in Bolton broth (BB) following ISO 10272-1:2017. The overgrowth of Campylobacter by ESBL-E. coli in the enrichment medium BB can lead to false-negative detection outcomes, but the cause for the growth suppression is yet unknown. A plausible reason could be the competition-induced lack of certain growth substrates. Therefore, this study aimed to investigate whether campylobacters and ESBL-E. coli compete for the same medium components and whether this is the cause for the observed growth repression. The availability of possible growth substrates in BB was determined and changes in their extracellular concentration were measured over time during mono-culture enrichment of C. jejuni, C. coli or ESBL-E. coli as well as in co-culture enrichments of campylobacters and ESBL-E. coli. Comparative analysis showed lactate and fumarate utilization by C. jejuni and C. coli exclusively, whereas ESBL-E. coli rapidly consumed asparagine, glutamine/arginine, lysine, threonine, tryptophan, pyruvate, glycerol, cellobiose, and glucose. Both campylobacters and ESBL-E. coli utilized aspartate, serine, formate, a-ketoglutarate and malate. Trends in compound utilization were similar for C. jejuni and C. coli and trends in compound utilization were rather comparable during enrichment of reference and freeze-stressed campylobacters. Since final cell densities of C. jejuni and C. coli in co-cultures were not enhanced by the addition of surplus L-serine and final cell densities were similar in fresh and spent medium, growth suppression seems not to be caused by a lack of substrates or production of inhibitory compounds. We hypothesized that oxygen availability was limiting growth in co-cultures. Higher oxygen availability increased the competitive fitness of C. jejuni 81-176 in co-culture with ESBL-E. coli in duplicate experiments, as cell concentrations in stationary phase were similar to those without competition. This could indicate the critical role of oxygen availability during the growth of Campylobacter and offers potential for further improvement of Campylobacter spp. enrichment efficacy.

This document provides guidance on undertaking risk assessment of all microbial hazards which may adversely affect human health in foods along a food chain. This document is also intended to provide practical guidance on a structured framework for carrying out risk assessment of microbiological hazards in foods, focussing on the four components including hazard identification, hazard characterization, exposure assessment and risk characterization. These guidelines therefore represent the best practice at the time of their preparation, and it is hoped that they will help stimulate further developments and disseminate the current knowledge.

The second edition of Microorganisms in Foods 7: Microbiological Testing in Food Safety Management updates and expands on information on the role of microbiological testing in modern food safety management systems. After helping the reader understand the often confusing statistical concepts underlying microbiological sampling, the second edition explores how risk assessment and risk management can be used to establish goals such as a “tolerable levels of risk,” Appropriate Levels of Protection, Food Safety Objectives or Performance Objectives for use in controlling foodborne illness. Guidelines for establishing effective management systems for control of specific hazards in foods are also addressed, including new examples for pathogens and indicator organisms in powdered infant formula, Listeria monocytogenes in deli-meats, enterohemorrhagic Escherichia coli in leafy green vegetables, viruses in oysters and Campylobacter in poultry. In addition, a new chapter on application of sampling concept to microbiological methods, expanded chapters covering statistical process control, investigational sampling, environmental sampling, and alternative sampling schemes.

Concerns about foodborne salmonellosis have led many countries to introduce microbiological criteria for certain food products. If such criteria are not well-grounded in science, they could be an unjustified obstacle to trade. Raw poultry products are an important part of the global food market. Import and export ambiguities and regulatory confusion resulting from different Salmonella requirements were the impetus for convening an international group of scientific experts from 16 countries to discuss the scientific and technical issues that affect the setting of a microbiological criterion for Salmonella contamination of raw chicken. A particular concern for the group was the use of criteria implying a zero tolerance for Salmonella and suggesting complete absence of the pathogen. The notion can be interpreted differently by various stakeholders and was considered inappropriate because there is neither an effective means of eliminating Salmonella from raw poultry nor any practical method for verifying its absence. Therefore, it may be more useful at present to set food safety metrics that involve reductions in hazard levels. Such terms as "zero tolerance" or "absence of a microbe" in relation to raw poultry should be avoided unless defined and explained by international agreement. Risk assessment provides a more meaningful approach than a zero tolerance philosophy, and new metrics, such as performance objectives that are linked to human health outcomes, should be utilized throughout the food chain to help define risk and identify ways to reduce adverse effects on public health

An efficient disinfection strategy within the food industry is needed to ensure food safety and prevent the spreading of foodborne pathogens such as Salmonella Typhimurium. However, several factors affect the efficiency of disinfection treatments resulting in low level exposure of the bacterial flora facilitating survival of bacterial cells. Therefore, this study analysed the effect of repeated exposure of S. Typhimurium cells to sub-lethal benzalkonium chloride (BKC) concentrations. One single BKC exposure showed tailing of the inactivation curve indicating variation in BKC susceptibility within the initial population. Repeated exposure resulted in the enrichment of a more resistant population and variants with increased BKC resistance were isolated. Phenotypical characterization of these resistant variants showed loss of motility, reduced biofilm forming capacity and reduced cell membrane permeability pointing to modification of cell surface properties. In conclusion, repeated exposure of S. Typhimurium to sub-lethal BKC concentrations rapidly selects for resistant variants. Occurrence and persistence of such variants in food processing environments can form a risk for public health.

Aims: To collect comparative data on thermal stability of structurally different viruses with proven or potential relevance to food safety. Methods and Results: Suspensions with poliovirus Sabin1, adenovirus type5, parechovirus1, human norovirus (NoV) GII.4, murine NoV (MNV1) and human influenza A (H1N1) viruses were heated at 56 and 73°C. Infectivity was tested by culture assay for all but human NoV GII.4 that cannot be cultivated in vitro. Time to first log10 reduction (TFL‐value) was calculated based on best fit using the monophasic, biphasic or Weibull models. The Weibull model provided the best fit at 56°C for all viruses except influenza virus. The TFL at 56°C varied between a high of 27 min (parechovirus) to a low of 10 s (adenovirus) and ranked parechovirus > influenza > MNV1 > poliovirus > adenovirus. The monophasic model best described the behaviour of the viruses at 73°C, in which case the TFL was MNV1(62s) > influenza > adenovirus > parechovirus > poliovirus(14s). Conclusions: Viruses do not follow log‐linear thermal inactivation kinetics and the thermostability of parechovirus and influenza virus is similar to that of proven foodborne viruses. Significance and Impact of the Study: Resistant fractions of viruses may remain infectious in thermal inactivation processes and inactivation of newly discovered or enveloped viruses in thermal food preparation processes should not be assumed without further testing.

This Opinion reviews the factors that affect microbial survival and growth in composite products, and in foods in general. It concludes that the main factors to be considered are: water activity, pH, temperature and duration of storage, processing, and intensity and duration of other non-thermal physical processes applied. Prevalence and concentration of the pathogens in food are important to determine the risk for consumers. The opinion presents a review of the quantitative microbiology models and databases that can be used to provide quantitative estimations of the impact of the above factors on the survival and growth of the main bacterial pathogens. In composite products, migration and diffusion of moisture and substances among the ingredients may change their physico-chemical parameters, particularly at the interfaces. Therefore, the assessment of the risk posed by composite products needs to consider the combinations of parameters most permissive to survival and growth of pathogens. Two complementary approaches are proposed for the identification and profiling of microbiological hazards in different specific composite products. The first one is based on past outbreaks and prevalence of hazards in the products and leads to the conclusion that the most frequent hazard-composite product combinations are Salmonella in cakes and bakery products. The second one consists in decision tools based on the impact on the pathogens of food composition and food processing. Categorisation of the risk for composite products requires information on their composition, processing and further handling, which can largely differ for foods belonging to the same category. Further conditions may influence the risk and should be verified, i.e. hygienic conditions during preparation of the composite products and their ingredients, shelf-life conditions, and reliability of cooking by consumers to inactivate pathogens. The decision tools developed apply to all composite products considered by the mandate, as well as to all other foods. © European Food Safety Authority, 2012

Objectives - The three objectives of this study are: first, to investigate how Cronobacter spp. are distributed throughout a recalled and a normal batch of powdered infant formula (PIF); second, to investigate the occurrence of conglomerations of Cronobacter spp. cells, since conglomerations of cells with high concentrations may impact on risk assessment and public health; and third, to investigate the performance of typical sampling plans. Results - In the recalled batch the concentrations Cronobacter spp. versus the filling time was assessed by 415 samples of 333 g using the MPN technique. In 58 % of the samples, concentrations were below the detection limit of -2.52 log CFU/g. However, specifically within three time intervals MPN concentrations were estimated varying between -2.52 and 0.66 log CFU/g. In addition 2290 samples of 1 g were investigated by plating, and 8 were found to contain Cronobacter spp. above the detection limit of 0.52 log CFU/g. These samples were originating from packages filled at the time interval with also the highest MPN concentrations. The two largest conglomerations were 123 and 560 cells in 1 g of PIF. In 99% of the samples from the normal batch, concentrations were below the detection limit. Various sampling plans were evaluated for the contamination data from the recalled batch. Keeping the total sample weight constant at 300 g and increasing the number of random samples from 1 to 300, increased the probability of detection from 0.38 till 1.00. Conclusions - Cronobacter spp. was distributed heterogeneously within a recalled batch of PIF with parts of the batch with no detectable contamination, and parts of the batch with concentrations up to 2.75 log CFU/g. The presence of conglomerations of Cronobacter spp. cells occurred with a low frequency. Taking more and smaller samples, keeping the total sampling weight constant, considerably improved the performance of the sampling plans to detect such a type of contaminated batch.

This document discusses mechanisms impacting on physical distributions of microorganisms in foods, characteristics and suitability of frequency distributions employed to model microbial distributions, and the impact of both physical and frequency distributions on illness risk and food safety management criteria. It examines the more common frequency distributions used and evaluates their strengths and weaknesses for modelling real situations against specific criteria.

High hydrostatic pressure (HHP) inactivation of three Listeria monocytogenes strains (EGDe, LO28, and Scott A) subjected to 350 MPa at 20°C in ACES buffer resulted in survival curves with significant tailing for all three strains. A biphasic linear model could be fitted to the inactivation data, indicating the presence of an HHP-sensitive and an HHP-resistant fraction, which both showed inactivation according to first-order kinetics. Inactivation parameters of these subpopulations of the three strains were quantified in detail. EGDe showed the highest D-values for the sensitive and resistant fraction, whereas LO28 and Scott A showed lower HHP resistance for both fractions. Survivors isolated from the tail of LO28 and EGDe were analyzed, and it was revealed that the higher resistance of LO28 was a stable feature for 24% (24 of 102) of the resistant fraction. These HHP-resistant variants were 10 to 600,000 times more resistant than wild type when exposed to 350 MPa at 20°C for 20 min. Contrary to these results, no stable HHP-resistant isolates were found for EGDe (0 of 102). The possible effect of HHP survival capacity of stress-resistant genotypic and phenotypic variants of L. monocytogenes on the safety of HHP-processed foods is discussed.

Predicting the growth and behaviour of microorganisms in food has long been an aim in food microbiology research. In recent years, microbial models have evolved to become more exact and the discipline of quantitative microbial ecology has gained increasing importance for food safety management, particularly as minimal processing techniques have become more widely used. These processing methods operate closer to microbial death, survival and growth boundaries and therefore require even more precise models. Part one discusses general issues involved in building models of microbial growth and inactivation in foods, with chapters on the historical background of the field, experimental design, data processing and model fitting, the problem of uncertainty and variability in models and modelling lag-time. Further chapters review the use of quantitative microbiology tools in predictive microbiology and the use of predictive microbiology in risk assessment. The second part of the book focuses on new approaches in specific areas of microbial modelling, with chapters discussing the implications of microbial variability in predictive modelling and the importance of taking into account microbial interactions in foods. Predicting microbial inactivation under high pressure and the use of mechanistic models are also covered. The final chapters outline the possibility of incorporating systems biology approaches into food microbiology.

The focus of this book is on state of the art technologies and scientific developments in academia and industry that contribute to the characterization and specification of fermentation starter microorganisms, to the present-day experimental approaches in product and process development and control, and to high throughput analytical techniques that facilitate the precise design of tailor-made fermented food products. Aspects covered include: microbial biodiversity of starter lactic acid bacteria, yeasts and moulds; product technology and functionality relating to flavour formation and control; health promoting aspects of foods and of probiotic and nutraceutical microbes; European legislation of fermented foods and ingredients; modelling and control of bacterial and fungal fermentation processes; and the relevance of ~omics (genomics, transcriptomics, proteomics, metabolomics) in starter design, metabolic control and safety assurance. This volume surely is an essential up-date for R&D professionals and advanced students of food science and technology.

Microbial quality and safety of foodstuffs can be improved by reducing the microbial load of the raw materials. Especially in products in which microbial spoilage is caused by sporeforming bacteria this can be the only solution. Combining existing datasets, expert knowledge and quantitative modeling techniques in a smart way have increased insight in the contamination of raw milk with the sporeforming butyric acid bacteria and Bacillus cereus. In this way the effect of various control points was quantified enabling a objective comparison of control points. Based on this information uncertainty about the true effect of various measures can be clarified and more effective measures can be identified

Het kwantificeren van de houdbaarheid van voedingsmiddelen. Dit aspect maakt deel uit van de voedselkwaliteit