Quantification of viable Brochothrix thermosphacta in cooked shrimp and salmon by real-time PCR

• Published in: Food Microbiology
• Main Authors: Mamlouk, Kelthoum, Mace, Sabrina, Guilbaud, Morgan, JAFFRES, Emmanuel, Ferchichi, Mounir, Prévost, Herve, Pilet, Marie-France, Dousset, Xavier
• Other Authors: Oniris, Secalim UMR1014, LUNAM Université Nantes Angers Le Mans, MICrobiologie de l'ALImentation au Service de la Santé (MICALIS), Institut National de la Recherche Agronomique (INRA)-AgroParisTech, SECurité des ALIments et Microbiologie, Institut National de la Recherche Agronomique (INRA), Region Pays de la Loire, France
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2012
• Subjects: RAPQUANTITATIVE DETECTION; STAA medium; Seafood; Spoilage; Brochothrix thermosphacta; Real-time PCR; 16S rRNA; COLD-SMOKED SALMON; LISTERIA-MONOCYTOGENES; PROPIDIUM MONOAZIDE; PANDALUS-BOREALIS; MICROBIAL ECOLOGY; MEAT; FOOD; CARNOBACTERIUM; LACTOCOCCUS; [SDV.SA]Life Sciences [q-bio]/Agricultural sciences; Pandalus borealis
• Online Access: https://hal.archives-ouvertes.fr/hal-01004204; https://doi.org/10.1016/j.fm.2011.09.012

Brochothrix thermosphacta, a Cram-positive bacterium, is considered as the predominant spoilage microbiota of modified atmosphere packing (MAP) shrimp and fish. Traditional methods currently used to detect B. thermosphacta in foods are time-consuming and labour-intensive. The aim of this study was to develop a real-time PCR quantification method combined with a propidium monoazide (PMA) sample treatment step to monitor the population of B. thermosphacta in cooked shrimp and salmon. The specificity of the two primers M0405 and M0404 used to amplify a 70 bp fragment of the 16S rRNA gene was demonstrated by using purified DNA from 30 strains, among 21 bacterial species including 22 reference strains. Using these primers for real-time PCR and in pure culture, a good correlation was obtained between real-time PCR and the conventional plating method. Quantification was linear over 7-log units using artificially inoculated samples. The method performed successfully when tested on naturally contaminated cooked shrimp and fresh salmon, with a minimum threshold of 1.9 x 10(2) CFU/g for accurate quantification of B. the rmosphacta. The correlation between the B. thermosphacta counts obtained by real-time PCR and plate counts on naturally contaminated shrimp and salmon was high (R-2=0.895). Thus, this study presents a rapid tool for producing reliable quantitative data on B. thermosphacta in cooked shrimp and fresh salmon. (C) 2011 Elsevier Ltd. All rights reserved.