Into the Jungle of Biological Agents of Foodborne Diseases: Time to Put Some Order for the French Risk Manager.

Consumers can be exposed to many foodborne biological hazards that cause diseases with varying outcomes and incidence and, therefore, represent different levels of public health burden. To help the French risk managers to rank these hazards and to prioritize food safety actions, we have developed a three-step approach. The first step was to develop a list of foodborne hazards of health concern in mainland France. From an initial list of 335 human pathogenic biological agents, the final list of "retained hazards" consists of 24 hazards, including 12 bacteria (including bacterial toxins and metabolites), 3 viruses and 9 parasites. The second step was to collect data to estimate the disease burden (incidence, Disability Adjusted Life Years) associated with these hazards through food during two time periods: 2008-2013 and 2014-2019. The ranks of the different hazards changed slightly according to the considered period. The third step was the ranking of hazards according to a multicriteria decision support model using the ELECTRE III method. Three ranking criteria were used, where two reflect the severity of the effects (Years of life lost and Years lost due to disability) and one reflects the likelihood (incidence) of the disease. The multicriteria decision analysis approach takes into account the preferences of the risk managers through different sets of weights and the uncertainties associated with the data. The method and the data collected allowed to estimate the health burden of foodborne biological hazards in mainland France and to define a prioritization list for the health authorities.

Assessment of the relationship between the MLST genetic diversity of Listeria monocytogenes and growth under selective and non-selective conditions.

Listeria monocytogenes can grow under stressful conditions and contaminate various food categories. Progresss in DNA sequencing-based identification methods, such as multi-locus sequence typing (MLST) now allow for more accurate characterization of pathogens. L. monocytogenes MLST genetic diversity is reflected by the different prevalence of the "clonal complexes" (CCs) in foods or infections. Better understanding of the growth potentials of L. monocytogenes is essential for quantitative risk assessment and efficient detection across CCs genetic diversity. Using optical density measurements taken with an automated spectrophotometer, we compared the maximal growth rate and lag phase of 39 strains from 13 different CCs and various food origins, in 3 broths mimicking stresful food conditions (8 °C, aw 0.95 and pH5) and in ISO Standard enrichment broths (Half Fraser and Fraser). This is important as growth could influence risk through pathogen multiplication in food. Besides, enrichment problems could lead to a lack of detection of some CCs. Despite small differences highlighting natural intraspecific variability, our results show that growth performances of L. monocytogenes strains under the conditions tested in selective and non-selective broth do not appear to be strongly correlated to CCs and cannot explain higher CC "virulence" or prevalence.

Salmonella enterica subsp. enterica Welikade: guideline for phylogenetic analysis of serovars rarely involved in foodborne outbreaks.

BACKGROUND: Salmonella spp. is a major foodborne pathogen with a wide variety of serovars associated with human cases and food sources. Nevertheless, in Europe a panel of ten serovars is responsible for up to 80% of confirmed human cases. Clustering studies by single nucleotide polymorphism (SNP) core-genome phylogenetic analysis of outbreaks due to these major serovars are simplified by the availability of many complete genomes in the free access databases. This is not the case for outbreaks due to less common serovars, such as Welikade, for which no reference genomes are available. In this study, we propose a method to solve this problem. We propose to perform a core genome MLST (cgMLST) analysis based on hierarchical clustering using the free-access EnteroBase to select the most suitable genome to use as a reference for SNP phylogenetic analysis. In this study, we applied this protocol to a retrospective analysis of a Salmonella enterica serovar Welikade (S. Welikade) foodborne outbreak that occurred in France in 2016. Finally, we compared the cgMLST and SNP analyses. SNP phylogenetic reconstruction was carried out considering the effect of recombination events identified by the ClonalFrameML tool. The accessory genome was also explored by phage content and virulome analyses. RESULTS: Our findings revealed high clustering concordance using cgMLST and SNP analyses. Nevertheless, SNP analysis allowed for better assessment of the genetic distance among strains. The results revealed epidemic clones of S. Welikade circulating within the poultry and dairy sectors in France, responsible for sporadic and non-sporadic human cases between 2012 and 2019. CONCLUSIONS: This study increases knowledge on this poorly described serovar and enriches public genome databases with 42 genomes from human and non-human S. Welikade strains, including the isolate collected in 1956 in Sri Lanka, which gave the name to this serovar. This is the first genomic analysis of an outbreak due to S. Welikade described to date.

Genomic elements located in the accessory repertoire drive the adaptation to biocides in Listeria monocytogenes strains from different ecological niches.

In response to the massive use of biocides for controlling Listeria monocytogenes (hereafter Lm) contaminations along the food chain, strains showing biocide tolerance emerged. Here, accessory genomic elements were associated with biocide tolerance through pangenome-wide associations performed on 197 Lm strains from different lineages, ecological, geographical and temporal origins. Mobile elements, including prophage-related loci, the Tn6188_qacH transposon and pLMST6_emrC plasmid, were widespread across lineage I and II food strains and associated with tolerance to benzalkonium-chloride (BC), a quaternary ammonium compound (QAC) widely used in food processing. The pLMST6_emrC was also associated with tolerance to another QAC, the didecyldimethylammonium-chloride, displaying a pleiotropic effect. While no associations were detected for chemically reactive biocides (alcohols and chlorines), genes encoding for cell-surface proteins were associated with BC or polymeric biguanide tolerance. The latter was restricted to lineage I strains from animal and the environment. In conclusion, different genetic markers, with polygenic nature or not, appear to have driven the Lm adaptation to biocide, especially in food strains but also from animal and the environment. These markers could aid to monitor and predict the spread of biocide tolerant Lm genotypes across different ecological niches, finally reducing the risk of such strains in food industrial settings.

Genetic, physiological, and cellular heterogeneities of bacterial pathogens in food matrices: Consequences for food safety.

In complex food systems, bacteria live in heterogeneous microstructures, and the population displays phenotypic heterogeneities at the single-cell level. This review provides an overview of spatiotemporal drivers of phenotypic heterogeneity of bacterial pathogens in food matrices at three levels. The first level is the genotypic heterogeneity due to the possibility for various strains of a given species to contaminate food, each of them having specific genetic features. Then, physiological heterogeneities are induced within the same strain, due to specific microenvironments and heterogeneous adaptative responses to the food microstructure. The third level of phenotypic heterogeneity is related to cellular heterogeneity of the same strain in a specific microenvironment. Finally, we consider how these phenotypic heterogeneities at the single-cell level could be implemented in mathematical models to predict bacterial behavior and help ensure microbiological food safety.

Dynamics of mobile genetic elements of Listeria monocytogenes persisting in ready-to-eat seafood processing plants in France.

BACKGROUND: Listeria monocytogenes Clonal Complexes (CCs) have been epidemiologically associated with foods, especially ready-to-eat (RTE) products for which the most likely source of contamination depends on the occurrence of persisting clones in food-processing environments (FPEs). As the ability of L. monocytogenes to adapt to environmental stressors met in the food chain challenges the efforts to its eradication from FPEs, the threat of persistent strains to the food industry and public health authorities continues to rise. In this study, 94 food and FPEs L. monocytogenes isolates, representing persistent subtypes contaminating three French seafood facilities over 2-6 years, were whole-genome sequenced to characterize their genetic diversity and determine the biomarkers associated with long-term survival in FPEs. RESULTS: Food and FPEs isolates belonged to five CCs, comprising long-term intra- and inter-plant persisting clones. Mobile genetic elements (MGEs) such as plasmids, prophages and transposons were highly conserved within CCs, some of which harboured genes for resistance to chemical compounds and biocides used in the processing plants. Some of these genes were found in a 90.8 kbp plasmid, predicted to be" mobilizable", identical in isolates from CC204 and CC155, and highly similar to an 81.6 kbp plasmid from isolates belonging to CC7. These similarities suggest horizontal transfer between isolates, accompanied by deletion and homologous recombination in isolates from CC7. Prophage profiles characterized persistent clonal strains and several prophage-loci were plant-associated. Notably, a persistent clone from CC101 harboured a novel 31.5 kbp genomic island that we named Listeria genomic island 3 (LGI3), composed by plant-associated loci and chromosomally integrating cadmium-resistance determinants cadA1C. CONCLUSIONS: Genome-wide analysis indicated that inter- and intra-plant persisting clones harbour conserved MGEs, likely acquired in FPEs and maintained by selective pressures. The presence of closely related plasmids in L. monocytogenes CCs supports the hypothesis of horizontal gene transfer conferring enhanced survival to FPE-associated stressors, especially in hard-to-clean harbourage sites. Investigating the MGEs evolutionary and transmission dynamics provides additional resolution to trace-back potentially persistent clones. The biomarkers herein discovered provide new tools for better designing effective strategies for the removal or reduction of resident L. monocytogenes in FPEs to prevent contamination of RTE seafood.

Modeling the Inactivation of Viruses from the Coronaviridae Family in Response to Temperature and Relative Humidity in Suspensions or on Surfaces.

Temperature and relative humidity are major factors determining virus inactivation in the environment. This article reviews inactivation data regarding coronaviruses on surfaces and in liquids from published studies and develops secondary models to predict coronaviruses inactivation as a function of temperature and relative humidity. A total of 102 D values (i.e., the time to obtain a log10 reduction of virus infectivity), including values for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), were collected from 26 published studies. The values obtained from the different coronaviruses and studies were found to be generally consistent. Five different models were fitted to the global data set of D values. The most appropriate model considered temperature and relative humidity. A spreadsheet predicting the inactivation of coronaviruses and the associated uncertainty is presented and can be used to predict virus inactivation for untested temperatures, time points, or any coronavirus strains belonging to Alphacoronavirus and Betacoronavirus genera.IMPORTANCE The prediction of the persistence of SARS-CoV-2 on fomites is essential in investigating the importance of contact transmission. This study collects available information on inactivation kinetics of coronaviruses in both solid and liquid fomites and creates a mathematical model for the impact of temperature and relative humidity on virus persistence. The predictions of the model can support more robust decision-making and could be useful in various public health contexts. A calculator for the natural clearance of SARS-CoV-2 depending on temperature and relative humidity could be a valuable operational tool for public authorities.

Exploring Listeria monocytogenes Transcriptomes in Correlation with Divergence of Lineages and Virulence as Measured in Galleria mellonella.

As for many opportunistic pathogens, the virulence potential of Listeria monocytogenes is highly heterogeneous between isolates and correlated, to some extent, with phylogeny and gene repertoires. In sharp contrast with copious data on intraspecies genome diversity, little is known about transcriptome diversity despite the role of complex genetic regulation in pathogenicity. The current study implemented RNA sequencing to characterize the transcriptome profiles of 33 isolates under optimal in vitro growth conditions. Transcript levels of conserved single-copy genes were comprehensively explored from several perspectives, including phylogeny, in silico-predicted virulence category based on epidemiological multilocus sequence typing (MLST) data, and in vivo virulence phenotype assessed in Galleria mellonella Comparing baseline transcriptomes between isolates was intrinsically more complex than standard genome comparison because of the inherent plasticity of gene expression in response to environmental conditions. We show that the relevance of correlation analyses and their statistical power can be enhanced by using principal-component analysis to remove the first level of irrelevant, highly coordinated changes linked to growth phase. Our results highlight the major contribution of transcription factors with key roles in virulence to the diversity of transcriptomes. Divergence in the basal transcript levels of a substantial fraction of the transcriptome was observed between lineages I and II, echoing previously reported epidemiological differences. Correlation analysis with in vivo virulence identified numerous sugar metabolism-related genes, suggesting that specific pathways might play roles in the onset of infection in G. mellonellaIMPORTANCEListeria monocytogenes is a multifaceted bacterium able to proliferate in a wide range of environments from soil to mammalian host cells. The accumulated genomic data underscore the contribution of intraspecies variations in gene repertoire to differential adaptation strategies between strains, including infection and stress resistance. It seems very likely that the fine-tuning of the transcriptional regulatory network is also a key component of the phenotypic diversity, albeit more difficult to investigate than genome content. Some studies reported incongruity in the basal transcriptome between isolates, suggesting a putative relationship with phenotypes, but small isolate numbers hampered proper correlation analyses with respect to their characteristics. The present study is the embodiment of the promising approach that consists of analyzing correlations between transcriptomes and various isolate characteristics. Statistically significant correlations were found with phylogenetic groups, epidemiological evidence of virulence potential, and virulence in Galleria mellonella larvae used as an in vivo model.

Inhibitory activity of phenolic acids against Listeria monocytogenes: Deciphering the mechanisms of action using three different models.

Phenolic compounds are well known for their antimicrobial activity. They may provide an interesting solution to ensure food safety by preventing the growth of foodborne pathogens while addressing the wishes of consumers for the use of natural preservatives in food and favoring the reuse of agro-industry byproducts. However, their mechanism of action is still not very well understood. Here, we aimed to decipher the complex mechanism of action of eight phenolic acids by decomposing their effects, such as the general effect of the decrease of extracellular pH (γ(pH)) and specific inhibitory effects of the undissociated (γ(Au)) and dissociated (γ(Ad)) forms. We thus developed three different models and applied them to a dataset of Listeria monocytogenes growth rates experimentally obtained in the presence of various concentrations of phenolic acids at several pHs. The model that best fits the dataset was selected for each phenolic acid to explore the potential mechanisms. The results show that the antimicrobial activity is mainly due to the effect of the undissociated forms, except for chlorogenic and gallic acids, for which the antimicrobial activity is mainly due to a decrease in extracellular pH. In addition, the dissociated forms of p-coumaric and ferulic acids show significant inhibitory activity.

Evaluation of methods for elution of HEV particles in naturally contaminated sausage, figatellu and pig liver.

Foodborne transmission of HEV is a growing public health concern in industrialised countries, where the disease is mainly autochthonous, caused by zoonotic HEV of either genotype 3 or 4. Foodstuffs containing pig's liver were suspected on several occasions to be the cause of autochthonous cases of HEV infection, while the transmission was associated with animal contact and the ingestion of raw or uncooked meat, especially liver. In assessing the risk related to the presence of HEV in food, detection methods were previously developed but HEV detection rates seem to vary with the type of samples and methods. As foodstuff containing pig liver can be contaminated with HEV internally, an efficient virus extraction procedure is required. The aim of this study was to evaluate six methods for their efficiency in releasing HEV viral particles from figatelli, pig liver sausages and liver samples previously tested positive for the presence of HEV. The ratio weight to volume of elution buffer (1:5) and the FastPrep®-24 homogeniser showed to significantly improve the quantity of HEV genomes released per gram of figatelli and pig liver sausages. To our knowledge, this study is the first to evaluate several methods for elution of HEV particles from naturally contaminated pig liver products, and may be extended for quantifying other viral genomes from food of animal origin.

Combining Quantitative Risk Assessment of Human Health, Food Waste, and Energy Consumption: The Next Step in the Development of the Food Cold Chain?

The preservation of perishable food via refrigeration in the supply chain is essential to extend shelf life and provide consumers with safe food. However, electricity consumed in refrigeration processes has an economical and an environmental impact. This study focuses on the cold chain of cooked ham, including transport, cold room in supermarket, display cabinet, transport by consumer, and domestic refrigerator, and aims to predict the risk for human health associated with Listeria monocytogenes, the amount of food wasted due to the growth of spoilage bacteria, and the electrical consumption to maintain product temperature through the cold chain. A set of eight intervention actions were tested to evaluate their impact on the three criteria. Results show that the modification of the thermostat of the domestic refrigerator has a high impact on food safety and food waste and a limited impact on the electrical consumption. Inversely, the modification of the airflow rate in the display cabinet has a high impact on electrical consumption and a limited impact on food safety and food waste. A cost-benefit analysis approach and two multicriteria decision analysis methods were used to rank the intervention actions. These three methodologies show that setting the thermostat of the domestic refrigerator to 4 °C presents the best compromise between the three criteria. The impact of decisionmaker preferences (criteria weight) and limitations of these three approaches are discussed. The approaches proposed by this study may be useful in decision making to evaluate global impact of intervention actions in issues involving conflicting outputs.

First gene-ontology enrichment analysis based on bacterial coregenome variants: insights into adaptations of Salmonella serovars to mammalian- and avian-hosts.

BACKGROUND: Many of the bacterial genomic studies exploring evolution processes of the host adaptation focus on the accessory genome describing how the gains and losses of genes can explain the colonization of new habitats. Consequently, we developed a new approach focusing on the coregenome in order to describe the host adaptation of Salmonella serovars. METHODS: In the present work, we propose bioinformatic tools allowing (i) robust phylogenetic inference based on SNPs and recombination events, (ii) identification of fixed SNPs and InDels distinguishing homoplastic and non-homoplastic coregenome variants, and (iii) gene-ontology enrichment analyses to describe metabolic processes involved in adaptation of Salmonella enterica subsp. enterica to mammalian- (S. Dublin), multi- (S. Enteritidis), and avian- (S. Pullorum and S. Gallinarum) hosts. RESULTS: The 'VARCall' workflow produced a robust phylogenetic inference confirming that the monophyletic clade S. Dublin diverged from the polyphyletic clade S. Enteritidis which includes the divergent clades S. Pullorum and S. Gallinarum (i). The scripts 'phyloFixedVar' and 'FixedVar' detected non-synonymous and non-homoplastic fixed variants supporting the phylogenetic reconstruction (ii). The scripts 'GetGOxML' and 'EveryGO' identified representative metabolic pathways related to host adaptation using the first gene-ontology enrichment analysis based on bacterial coregenome variants (iii). CONCLUSIONS: We propose in the present manuscript a new coregenome approach coupling identification of fixed SNPs and InDels with regards to inferred phylogenetic clades, and gene-ontology enrichment analysis in order to describe the adaptation of Salmonella serovars Dublin (i.e. mammalian-hosts), Enteritidis (i.e. multi-hosts), Pullorum (i.e. avian-hosts) and Gallinarum (i.e. avian-hosts) at the coregenome scale. All these polyvalent Bioinformatic tools can be applied on other bacterial genus without additional developments.

Population Genetic Structure of Listeria monocytogenes Strains as Determined by Pulsed-Field Gel Electrophoresis and Multilocus Sequence Typing.

UNLABELLED: Listeria monocytogenes is a ubiquitous bacterium that may cause the foodborne illness listeriosis. Only a small amount of data about the population genetic structure of strains isolated from food is available. This study aimed to provide an accurate view of the L. monocytogenes food strain population in France. From 1999 to 2014, 1,894 L. monocytogenes strains were isolated from food at the French National Reference Laboratory for L. monocytogenes and classified according to the five risk food matrices defined by the European Food Safety Authority (EFSA). A total of 396 strains were selected on the basis of different pulsed-field gel electrophoresis (PFGE) clusters, serotypes, and strain origins and typed by multilocus sequence typing (MLST), and the MLST results were supplemented with MLST data available from Institut Pasteur, representing human and additional food strains from France. The distribution of sequence types (STs) was compared between food and clinical strains on a panel of 675 strains. High congruence between PFGE and MLST was found. Out of 73 PFGE clusters, the two most prevalent corresponded to ST9 and ST121. Using original statistical analysis, we demonstrated that (i) there was not a clear association between ST9 and ST121 and the food matrices, (ii) serotype IIc, ST8, and ST4 were associated with meat products, and (iii) ST13 was associated with dairy products. Of the two major STs, ST121 was the ST that included the fewest clinical strains, which might indicate lower virulence. This observation may be directly relevant for refining risk analysis models for the better management of food safety. IMPORTANCE: This study showed a very useful backward compatibility between PFGE and MLST for surveillance. The results enabled better understanding of the population structure of L. monocytogenes strains isolated from food and management of the health risks associated with L. monocytogenes food strains. Moreover, this work provided an accurate view of L. monocytogenes strain populations associated with specific food matrices. We clearly showed that some STs were associated with food matrices, such as meat, meat products, and dairy products. We opened the way to source attribution modeling in order to quantify the relative importance of the main food matrices.

Bacillus cereus-induced food-borne outbreaks in France, 2007 to 2014: epidemiology and genetic characterisation.

The aim of this study was to identify and characterise Bacillus cereus from a unique national collection of 564 strains associated with 140 strong-evidence food-borne outbreaks (FBOs) occurring in France during 2007 to 2014. Starchy food and vegetables were the most frequent food vehicles identified; 747 of 911 human cases occurred in institutional catering contexts. Incubation period was significantly shorter for emetic strains compared with diarrhoeal strains A sub-panel of 149 strains strictly associated to 74 FBOs and selected on Coliphage M13-PCR pattern, was studied for detection of the genes encoding cereulide, diarrhoeic toxins (Nhe, Hbl, CytK1 and CytK2) and haemolysin (HlyII), as well as panC phylogenetic classification. This clustered the strains into 12 genetic signatures (GSs) highlighting the virulence potential of each strain. GS1 (nhe genes only) and GS2 (nhe, hbl and cytK2), were the most prevalent GS and may have a large impact on human health as they were present in 28% and 31% of FBOs, respectively. Our study provides a convenient molecular scheme for characterisation of B. cereus strains responsible for FBOs in order to improve the monitoring and investigation of B. cereus-induced FBOs, assess emerging clusters and diversity of strains.

Updated Parameters for Listeria monocytogenes Dose-Response Model Considering Pathogen Virulence and Age and Sex of Consumer.

Better knowledge regarding the Listeria monocytogenes dose-response (DR) model is needed to refine the assessment of the risk of foodborne listeriosis. In 2018, the European Food Safety Agency (EFSA) derived a lognormal Poisson DR model for 14 different age-sex sub-groups, marginally to strain virulence. In the present study, new sets of parameters are developed by integrating the EFSA model for these sub-groups together with three classes of strain virulence characteristics ("less virulent", "virulent", and "more virulent"). Considering classes of virulence leads to estimated relative risks (RRs) of listeriosis following the ingestion of 1000 bacteria of "less virulent" vs. "more virulent" strains ranging from 21.6 to 24.1, depending on the sub-group. These relatively low RRs when compared with RRs linked to comorbidities described in the literature suggest that the influence of comorbidity on the occurrence of invasive listeriosis for a given exposure is much more important than the influence of the virulence of the strains. The updated model parameters allow better prediction of the risk of invasive listeriosis across a population of interest, provided the necessary data on population demographics and the proportional contribution of strain virulence classes in food products of interest are available. An R package is made available to facilitate the use of these dose-response models.

A Critical Review of Risk Assessment Models for Listeria monocytogenes in Produce.

A review of quantitative risk assessment (QRA) models of Listeria monocytogenes in produce was carried out, with the objective of appraising and contrasting the effectiveness of the control strategies placed along the food chains. Despite nine of the thirteen QRA models recovered being focused on fresh or RTE leafy greens, none of them represented important factors or sources of contamination in the primary production, such as the type of cultivation, water, fertilisers or irrigation method/practices. Cross-contamination at processing and during consumer's handling was modelled using transfer rates, which were shown to moderately drive the final risk of listeriosis, therefore highlighting the importance of accurately representing the transfer coefficient parameters. Many QRA models coincided in the fact that temperature fluctuations at retail or temperature abuse at home were key factors contributing to increasing the risk of listeriosis. In addition to a primary module that could help assess current on-farm practices and potential control measures, future QRA models for minimally processed produce should also contain a refined sanitisation module able to estimate the effectiveness of various sanitisers as a function of type, concentration and exposure time. Finally, L. monocytogenes growth in the products down the supply chain should be estimated by using realistic time-temperature trajectories, and validated microbial kinetic parameters, both of them currently available in the literature.

The impact of the proposed revised Australia's microbiological monitoring programme for beef and sheep meat exported to the EU.

The European Commission asks scientific and technical assistance from EFSA to determine the impact of the revision of the Australian monitoring programme on its ability to detect microbiological contamination. Considering that, in 2010, the European Commission determined the current Australian monitoring programme to be equivalent to the EU requirements for microbiological monitoring further to an EFSA scientific assessment, the current and proposed programmes were described and the total number of alerts was compared using a probabilistic modelling approach. In the current programme, only beef and sheep carcasses are monitored using three-class moving window sampling plans, while in the proposed programme, carcass, bulk meat, primal and offal are monitored using four two-class sampling plans and Salmonella testing is excluded. The models revealed that the current programme provides a higher number of alerts for APC, while the proposed monitoring programme provides a higher number of alerts for E. coli. For APC and E. coli combined, the mean, 5th and 95th centiles of the uncertainty distribution of the total number of alerts in the current and the proposed monitoring programme are 201 [179, 227] and 172 [149, 194] for beef, and 199 [175, 222] and 2897 [2795, 3008] for sheep, respectively. For Salmonella, there are no alerts for the proposed programme since sampling is excluded while for the current programme, the estimated mean, 5th and 95th centiles of the uncertainty distribution of the number of alerts for a 5-year period were 143 [126, 144] for heifer/steer, 1.6 [0, 4] for cow/bull and 0 [0, 0] for lamb/sheep. Overall, for APC and E. coli, the estimated total number of alerts was similar (beef) or higher (sheep) for the proposed compared to the current programme. In contrast, Salmonella sampling is excluded from the proposed programme and thus cannot detect the number of current alerts.

A Critical Review of Risk Assessment Models for Listeria monocytogenes in Meat and Meat Products.

A review of the published quantitative risk assessment (QRA) models of L. monocytogenes in meat and meat products was performed, with the objective of appraising the intervention strategies deemed suitable for implementation along the food chain as well as their relative effectiveness. A systematic review retrieved 23 QRA models; most of them (87%) focused on ready-to-eat meat products and the majority (78%) also covered short supply chains (end processing/retail to consumption, or consumption only). The processing-to-table scope was the choice of models for processed meats such as chorizo, bulk-cooked meat, fermented sausage and dry-cured pork, in which the effects of processing were simulated. Sensitivity analysis demonstrated the importance of obtaining accurate estimates for lag time, growth rate and maximum microbial density, in particular when affected by growth inhibitors and lactic acid bacteria. In the case of deli meats, QRA models showed that delicatessen meats sliced at retail were associated with a higher risk of listeriosis than manufacture pre-packed deli meats. Many models converged on the fact that (1) controlling cold storage temperature led to greater reductions in the final risk than decreasing the time to consumption and, furthermore, that (2) lower numbers and less prevalence of L. monocytogenes at the end of processing were far more effective than keeping low temperatures and/or short times during retail and/or home storage. Therefore, future listeriosis QRA models for meat products should encompass a processing module in order to assess the intervention strategies that lead to lower numbers and prevalence, such as the use of bio-preservation and novel technologies. Future models should be built upon accurate microbial kinetic parameters, and should realistically represent cross-contamination events along the food chain.

A Critical Review of Risk Assessment Models for Listeria monocytogenes in Seafood.

Invasive listeriosis, due to its severe nature in susceptible populations, has been the focus of many quantitative risk assessment (QRA) models aiming to provide a valuable guide in future risk management efforts. A review of the published QRA models of Listeria monocytogenes in seafood was performed, with the objective of appraising the effectiveness of the control strategies at different points along the food chain. It is worth noting, however, that the outcomes of a QRA model are context-specific, and influenced by the country and target population, the assumptions that are employed, and the model architecture itself. Studies containing QRA models were retrieved through a literature search using properly connected keywords on Scopus and PubMed®. All 13 QRA models that were recovered were of short scope, covering, at most, the period from the end of processing to consumption; the majority (85%) focused on smoked or gravad fish. Since the modelled pathways commenced with the packaged product, none of the QRA models addressed cross-contamination events. Many models agreed that keeping the product's temperature at 4.0-4.5 °C leads to greater reductions in the final risk of listeriosis than reducing the shelf life by one week and that the effectiveness of both measures can be surpassed by reducing the initial occurrence of L. monocytogenes in the product (at the end of processing). It is, therefore, necessary that future QRA models for RTE seafood contain a processing module that can provide insight into intervention strategies that can retard L. monocytogenes' growth, such as the use of bacteriocins, ad hoc starter cultures and/or organic acids, and other strategies seeking to reduce cross-contamination at the facilities, such as stringent controls for sanitation procedures. Since risk estimates were shown to be moderately driven by growth kinetic parameters, namely, the exponential growth rate, the minimum temperature for growth, and the maximum population density, further work is needed to reduce uncertainties.