-The characterisation of naturally occurring bacterial species present in cheese made from raw milk and/or the study of the equilibrium of the floras present during the ripening process necessitates the use of reliable culture media. Currently, there are relatively few methods available for specifically counting these microorganisms in the dairy environment. Three media were developed. These media were compared with Chapman and TSA/NaCl media for their ability to select and to allow the growth of the researched germs in 25 samples of different cheeses (Camembert, Pont l'Évêque, Livarot, Comté, Saint-Nectaire, Salers), as well as in 4 samples of raw milk. The CRBM medium (Cheese Ripening Bacteria Medium) permitted the recuperation of all ripening bacteria; this medium supplemented with bacitracine selected for the staphylococci, while supplemented with furazolidone, it permitted the numeration of corynebacteria present including the Micrococcaceae. These media were more selective against undesirable floras (enterobacteria, Bacillus spp., streptococci, yeasts and molds) and allowed a better growth of the studied bacteria. For all the types of cheese studied, the specificity of the media was satisfactory. The use of CRBM media therefore appears interesting in view of the microbiological characterisation of milk or cheeses made from raw milk.corynebacteria / Micrococcaceae / cheese / ripening / numeration Résumé -Nouveaux milieux pour le dénombrement de la flore de surface des fromages. Le recensement des espèces naturellement présentes dans les fromages au lait cru et/ou l'étude de l'équi-libre des flores au cours de l'affinage nécessitent de disposer de milieux fiables. Or, il existe relativement peu de milieux de dénombrement spécifiques pour ces micro-organismes dans le domaine laitier. Trois milieux ont été développés. La performance de ces milieux, en terme de sélectivité Comté, Saint-Nectaire, Salers) et pour 4 échantillons de lait cru, en comparaison avec les milieux Chapman et TSA/NaCl. Le milieu CRBM permettait la récupération des bactéries d'affinage dans leur ensemble ; supplémenté en bacitracine, il sélectionnait les staphylocoques tandis que la furazolidone permettait de dénombrer les bactéries corynéformes, y compris les Micrococcaceae. Le milieu CRBM et le milieu CRBM modifié par addition d'antibiotiques étaient plus sélectifs vis-à-vis de flores indésirables (entérobactéries, Bacillus, streptocoques, levures-moisissures). Ils présentaient par ailleurs une meilleure électivité vis-à-vis des bactéries d'affinage, la diversité des espèces recensées étant plus importante. Pour tous les fromages étudiés, la spécificité des milieux était satisfaisante. L'utilisation des milieux CRBM apparaît intéressante pour la caractérisation microbiologique des laits ou des fromages au lait cru.bactérie corynéforme / Micrococcaceae / fromage / affinage / dénombrement
Noroviruses (NoVs), currently recognised as the most common human food-borne pathogens, are ubiquitous in the environment and can be transmitted to humans through multiple foodstuffs. In this study, we evaluated the prevalence of human NoV genogroups I (GI) and II (GII) in 493 food samples including soft red fruits (n = 200), salad vegetables (n = 210) and bivalve mollusc shellfish (n = 83), using the Bovine Enterovirus type 1 as process extraction control for the first time. Viral extractions were performed by elution concentration and genome detection by TaqMan Real-Time RT-PCR (RT-qPCR). Experimental contamination using hepatitis A virus (HAV) was used to determine the limit of detection (LOD) of the extraction methods. Positive detections were obtained from 2 g of digestive tissues of oysters or mussels kept for 16 h in seawater containing 2.0-2.7 log10 plaque-forming units (PFU)/L of HAV. For lettuces and raspberries, the LOD was, respectively, estimated at 2.2 and 2.9 log10 PFU per 25 g. Of the molluscs tested, 8.4 and 14.4% were, respectively, positive for the presence of GI NoV and GII NoV RNA. Prevalence in GI NoVs varied from 11.9% for the salad vegetables samples to 15.5% for the red soft fruits. Only 0.5% of the salad and red soft fruits samples were positive for GII NoVs. These results highlight the high occurrence of human NoVs in foodstuffs that can be eaten raw or after a moderate technological processing or treatment. The determination of the risk of infection associated with an RT-qPCR positive sample remains an important challenge for the future.
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