Single-Cell Growth Probability of Listeria monocytogenes at Suboptimal Temperature, pH, and Water Activity

The single-cell growth probability of Listeria monocytogenes was characterized in tryptone soy broth supplemented with 0.6% yeast extract at temperature ranging from 5 to 25°C, pH ranging from 4.4 to 6.5, and water activity ranging from 0.919 to 0.989. Growth was monitored visually in 96-microwell plates and the growth probability was deduced from concentrations estimated with the MPN calculation. Models were proposed to describe the increase of the probability from 0 to 1 with increasing values of environmental factors. An exponential model was used for the temperature and the individual minimal temperature for growth ranged from −3.6°C [−4.5°C, −2.7°C] to 17.3°C [16.0°C, 18.6°C]. An inverse exponential model was convenient for the pH and the minimal pH for growth of individual cells ranged from 4.34 [3.93, 4.75] to 5.93 [4.85, 7.01]. A linear model was used for the water activity and the minimal value for growth of individual cells ranged from 0.917 [0.909, 0.925] to 0.988 [0.966, 1]. In spite of the great between-experiment variability, the minimal values estimated for the growth limits of individual cells were in accordance with values usually proposed for L. monocytogenes populations. This study provides models allowing the prediction of the growth probability of a few cells contaminating chilled foods with suboptimal pH and water activity improving thus the assessment of the behavior of L. monocytogenes cells naturally contaminating foods

Significance of predictive microbiology for the assessment of the exposure of food to Listeria monocytogenes

The connection between equine uveitis and leptospirosis can be established using various techniques: isolation of the organism ; detection of agglutinative antibodies (micro-agglutination test or MAT) provided antibody levels are very high or rising very fast ; detection of antibodies directed against leptospiral proteins other than lipopolysaccharides (Dot-Blot) ; and finally by genic amplification (Polymerase Chain Reaction). The results obtained with these various methods are discussed here.L'appréciation des risques microbiologiques est fondée sur l'évaluation de la présence de micro-organismes pathogènes dans les aliments. Cette évaluation repose en grande partie sur une appréciation de l'exposition aux micro-organismes qui nécessite le recueil d'une quantité importante d'informations sur la nature de l'aliment, sur son circuit de distribution, sur ses modes de consommation ainsi que sur le micro-organisme et son comportement dans l'aliment. Cette étude théorique sur Listeria monocytogenes illustre la méthode d'appréciation de l'exposition et présente son intérêt pour l'évaluation objective de l'impact de certaines options de maîtrise

Food safety objectives and management of the risk of staphylococcal food poisoning from cream-filled baked goods

The concept of food safety objectives recently proposed by the International Commission on Microbiological Specifications for Foods (ICMSF) is designed to convert the appropriate level of protection of the consumer health into a sanitary objective applicable to foods. Food safety objectives are hence defined as maximum frequencies and/or concentrations of microbiological hazards in foodstuffs at the time of consumption. This concept is illustrated using a recently published study on the risk of staphylococcal food poisoning from cream-filled baked goods. Although interesting for its educational aspect, this example evades however some technical difficulties hidden behind such an approach. The definition of food safety objectives demonstrates an important progress in the management of food safety, but refinements must be made to properly integrate this concept into risk estimation schemes.Le concept d'objectifs de sécurité des aliments récemment proposé par la Commission internationale pour la définition des caractéristiques microbiologiques des aliments (ICMSF) permet de convertir le niveau approprié de protection de la santé des consommateurs en objectif sanitaire applicable au niveau des aliments. Les objectifs de sécurité des aliments correspondent donc à des fréquences et/ou des concentrations maximales de dangers microbiologiques présents dans des aliments au moment de leur consommation. Cet article illustre ce concept à partir d'un exemple publié récemment concernant le risque d'intoxination staphylococcique liée à la consommation de pâtisseries à la crème. Cet exemple, intéressant par son aspect pédagogique, élude cependant certaines difficultés techniques qui se cachent derrière une telle approche. La définition de ces objectifs de sécurité des aliments constitue donc une évolution notable dans la démarche de gestion de la sécurité sanitaire des aliments mais des réflexions doivent encore être menées afin de l'intégrer correctement dans les démarches d'estimation des risques

Modelling of Listeria monocytogenes growth infoods

Les modèles de microbiologie prévisionnelle permettent de simuler la croissance des populations de Listeria monocytogenes dans les aliments. L’approche progressive avec interactions semble la plus fiable pour simuler ces comportements, mais celle-ci se heurte encore à certaines limites comme l’aspect stochastique de la modélisation de la croissance ou l’intégration de l’effet de traitements induisant des stress bactériens. Malgré cela, l’outil se révèle utile dans la détermination des durées de vie des denrées alimentaires.Predictive modelling allows to simulate the growth of Listeria monocytogenes in foods. The multiplicative type model including interactions between environmental factors seems the more reliable to simulate these growths, but there are still some lacks as the stochastic modelling or the inclusion of the effect of process inducing bacterial injury. In spite of this, the tool is prove to be useful for the calculation of food shelf fifes

Reconstruction bathymétrique sonar en présence de trajets multiples et de bruit impulsif

National audienceCet article propose une méthode de poursuite de l'angle d'arrivée de l'écho principal rétrodiffusé par le fond marin pour la reconstruction bathymétrique. Cette méthode présente certains avantages par rapport aux techniques classiques d'estimation de l'angle d'arrivée et permet en particulier de régulariser la trajectoire de l'angle estimé et ainsi réduire le niveau d'interférence causé par les échos secondaires

Teaching and diagnosis of lesions in slaughterhouses: ASADIA® software

In 2000-2002, over 1600 slides on pathology applied to meat inspection, coming from various sources, have been put together in a CD-Rom and circulated to all veterinary inspection services in France. The objective was to keep a trace of increasingly rare lesions and unify the terminology, as well as provide a teaching tool for meat inspectors.Une mise en commun de diverses collections de diapositives en rapport avec l'anatomie pathologique appliquée à l'inspection des viandes a été réalisée entre 2000 et 2002. Un CD-Rom a été réalisé et a fait l'objet d'une diffusion à l'ensemble des services de contrôle en France. Il rassemble plus de 1 600 photographies. Son objectif est de conserver la mémoire de la morphologie de lésions en voie de raréfaction, d'aider à l'apprentissage des personnels d'inspection et d'harmoniser les termes employés

Control of the repeatability of high frequency multibeam echosounder backscatter by using natural reference areas

The increased use of backscatter measurements in time series for environmental monitoring necessitates the comparability of individual results. With the current lack of pre-calibrated multibeam echosounder systems for absolute backscatter measurement, a pragmatic solution is the use of natural reference areas for ensuring regular assessment of the backscatter measurement repeatability. This method mainly relies on the assumption of a sufficiently stable reference area regarding its backscatter signature. The aptitude of a natural area to provide a stable and uniform backscatter response must be carefully considered and demonstrated by a sufficiently long time-series of measurements. Furthermore, this approach requires a strict control of the acquisition and processing parameters. If all these conditions are met, stability check and relative calibration of a system are possible by comparison with the averaged backscatter values for the area. Based on a common multibeam echosounder and sampling campaign completed by available bathymetric and backscatter time series, the suitability as a backscatter reference area of three different candidates was evaluated. Two among them, Carré Renard and Kwinte, prove to be excellent choices, while the third one, Western Solent, lacks sufficient data over time, but remains a valuable candidate. The case studies and the available backscatter data on these areas prove the applicability of this method. The expansion of the number of commonly used reference areas and the growth of the number of multibeam echosounder controlled thereon could greatly contribute to the further development of quantitative applications based on multibeam echosounder backscatter measurements

Risk factors for sporadic listeriosis: a systematic review and meta-analysis

Listeriosis is a major public health concern associated with high hospitalization and mortality rates. The objective of this work was to summarize evidence on the associations between risk factors and sporadic cases by meta-analysing outcomes from currently published case-control studies. Suitable scientific articles were identified through systematic literature search, and subjected to a methodological quality assessment. From each study, odds-ratio (OR) measures as well as study characteristics such as population type, design, type of model and risk factor hierarchy were extracted. Mixed-effects meta-analysis models were adjusted by population type to appropriate data partitions. Twelve primary studies investigating sporadic listeriosis conducted between 1985 and 2013 passed through a quality assessment stage. These studies provided 226 OR considered for meta-analysis. According to the meta-analysis, the main risk factor for acquiring listeriosis is suffering from an immunocompromising disease. In relation to the food exposures, this meta-analysis confirmed known risk factors such as consumption of RTE dairy, seafood and processed meat and underlined new food vehicles as fruits and vegetables, recently involved in outbreaks. There were not enough data to appraise travel, animal-contact and person-to-person as transmission pathways for listeriosis. These results will allow refining the case-control studies in the aim of improving risk factors characterisation for listeriosis in the susceptible population.U. Gonzales-Barron and V. Cadavez are grateful to the Foundation for Science and Technology (FCT, Portugal) for financial support through national funds FCT/MCTES to CIMO (UIDB/00690/2020). U. Gonzales- Barron also thanks FCT, P.I., for the institutional scientific employment program.info:eu-repo/semantics/publishedVersio

Reuse of medical face masks in domestic and community settings without sacrificing safety: Ecological and economical lessons from the Covid-19 pandemic

The need for personal protective equipment increased exponentially in response to the Covid-19 pandemic. To cope with the mask shortage during springtime 2020, a French consortium was created to find ways to reuse medical and respiratory masks in healthcare departments. The consortium addressed the complex context of the balance between cleaning medical masks in a way that maintains their safety and functionality for reuse, with the environmental advantage to manage medical disposable waste despite the current mask designation as single-use by the regulatory frameworks. We report a Workflow that provides a quantitative basis to determine the safety and efficacy of a medical mask that is decontaminated for reuse. The type IIR polypropylene medical masks can be washed up to 10 times, washed 5 times and autoclaved 5 times, or washed then sterilized with radiations or ethylene oxide, without any degradation of their filtration or breathability properties. There is loss of the antiprojection properties. The Workflow rendered the medical masks to comply to the AFNOR S76-001 standard as “type 1 non-sanitory usage masks”. This qualification gives a legal status to the Workflow-treated masks and allows recommendation for the reuse of washed medical masks by the general population, with the significant public health advantage of providing better protection than cloth-tissue masks. Additionally, such a legal status provides a basis to perform a clinical trial to test the masks in real conditions, with full compliance with EN 14683 norm, for collective reuse. The rational reuse of medical mask and their end-of-life management is critical, particularly in pandemic periods when decisive turns can be taken. The reuse of masks in the general population, in industries, or in hospitals (but not for surgery) has significant advantages for the management of waste without degrading the safety of individuals wearing reused masks