![]() ![]() In the field of microbiological analysis, the non-cultural molecular methods such as quantitative real-time PCR (qPCR) have become essential tools in the last decade to detect and quantify microorganisms, with high precision in complex microbiota, e.g., in food matrices or food processing plants ( Kuchta et al., 2014 Franco-Duarte et al., 2019). This bacterium has also been isolated from food processing plants (from floors, walls, machines, etc.) which constitute one of the main sources of food contamination during processing ( Stackebrandt and Jones, 2006 Nychas et al., 2008). thermosphacta has been described as widely disseminated along the food chain, from the raw material to the final product and during storage until use by date. thermosphacta can also produce butter/plastic/rancid, blue-cheese, sour/pungent off-odors ( Joffraud et al., 2001, 2006 Stohr et al., 2001). thermosphacta, such as cooked and peeled shrimp with the production of strong butter, buttermilk-like, sour, and nauseous off-odors ( Mejlholm et al., 2005 Laursen et al., 2006 Jaffrès et al., 2011). Seafood products, whose consumption is constantly increasing worldwide, can also be spoiled by B. thermosphacta can produce dairy – cheesy and creamy – off-odors ( Dainty and Mackey, 1992 Casaburi et al., 2014). This bacterium can produce off-odors leading to food waste, which moreover contributes to the ecological impact of food spoilage ( Remenant et al., 2015 Illikoud et al., 2018a). thermosphacta in foods.īrochothrix thermosphacta is one of the main food spoilage bacteria, and can cause important economic losses in the food industry. Thus, this study presents a rapid, specific and efficient rpoC-PMA-qPCR method validated in cold-smoked salmon to quantify viable B. thermosphacta cells in cold-smoked salmon. Nevertheless, our results did not highlight any difference between PMAxx and PMA in their efficiency to discriminate viable from unviable B. When dead cells were used, both viability dyes suppressed DNA amplification. Using the three primer sets on viable cells, no significant difference was observed between cells treated or untreated with PMA or PMAxx. thermosphacta cells in SSTH was 103.50%, with a linear determination coefficient (r 2) of 0.998 and a limit of detection of 4.04 log CFU/g. The efficiency of new designed rpoC qPCR on viable B. The three primer sets displayed similar specificity and efficiency. thermosphacta cells in BHI broth and smoked salmon tissue homogenate (SSTH). The viability dyes PMA or PMAxx were combined with qPCR and compared with these primer sets on viable and dead B. QPCR efficiency and specificity were compared with two other published primer sets targeting the rpoC and rpoB genes. We designed a new PCR primer set from the single-copy rpoC gene. thermosphacta is time-consuming and can underestimate cells in a viable but not immediately culturable state. The culture method commonly used to quantify B. Specific and sensitive tools that detect and quantify this bacterium in food products are very useful. Among seafood products, cold-smoked salmon is particularly impacted by B. thermosphacta is one of the main food spoilage bacteria. The aim of this study was to develop a rapid and accurate PMA-qPCR method to quantify viable Brochothrix thermosphacta in cold-smoked salmon. UMR 1014, Secalim, INRAE, Oniris, Nantes, France. ![]() Agnès Bouju-Albert, Sabrina Saltaji, Xavier Dousset, Hervé Prévost and Emmanuel Jaffrès * ![]()
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