| Abstrakt: |
The microflora of cold smoked salmon (CSS) consists of Gram-negative bacteria such as Photobacterium, Vibrio and Shewanella, and Gram-positive bacteria from the genera Carnobacterium, Lactobacillus and Brochothrix. In this work, 5 series of CSS samples from different suppliers were stored for 1 week at 4 ?C and 4 weeks at 7 ?C. The enumeration of lactic acid bacteria (LAB) from each sample was carried out every week followed by isolation. Molecular identification was carried out on isolates obtained from 15 CSS samples stored at refrigeration temperature for 14 to 35 d. 158 Gram-positive bacteria were identified by PCR using specific primers and PCR-RFLP on the 16S-23S rDNA intergenic spacer region (ISR). 28 Carnobacterium piscicola strains, 15 Cb. divergens strains, 81 Lactobacillus curvatus strains and only 1 Lb. sakei strain were identified. In addition, 33 Gram-positive catalase-positive isolates were identified as Brochothrix thermosphacta. The modification of bacterial diversity in CSS during storage was also monitored by using the temporal temperature gradient gel electrophoresis (TTGE) technique. The migration allowed both Gram-positive bacteria (Cb. piscicola, Cb. divergens, Lb. curvatus, Lb. sakei and B. thermosphacta) and Gram-negative bacteria (P. phosphoreum and S. putrefaciens) to be differentiated. All the bacteria species (Cb. piscicola, Lb. curvatus and P. phosphoreum) identified after culture could be specifically detected by TTGE. ?tude de l'?volution bact?rienne et identification mol?culaire des bact?ries lactiques du saumon fum? au cours de sa conservation. La flore du saumon fum? est constitu?e d'une flore Gram n?gatif compos?e principalement des genres Photobacterium, Vibrio et Shewanella et de bact?ries ? Gram positif des genres Carnobacterium, Lactobacillus et Brochothrix. Cette recherche a concern? 5 s?ries d'?chantillons de saumon fum? de diff?rentes usines conserv?es 1 semaine ? 4 ?C et 4 semaines ? 7 ?C. Le d?nombrement des bact?ries lactiques a ?t? r?alis? chaque semaine sur chaque ?chantillon suivi par des isolements. L'identification mol?culaire sp?cifique de ces isolats a ?t? conduite sur 15 ?chantillons conserv?s pendant une dur?e de 14 ? 35 j. 158 isolats de bact?ries Gram positif ont ?t? identifi?s en utilisant amorces sp?cifiques et PCR-RFLP sur la s?quence interg?nique 16S-23S rDNA. Ce travail a donc permis d'identifier 28 isolats de Carnobacterium piscicola, 15 isolats de Cb. divergens, 81 isolats de Lactobacillus curvatus et un isolat de Lb. sakei. De plus, 33 isolats Gram positif catalase positif ont ?t? identifi?s comme ?tant des souches de Brochothrix thermosphacta. Le changement de la diversit? bact?rienne dans le saumon fum? pendant le stockage a ?t? suivi par la m?thode TTGE (temporal temperature gradient gel electrophoresis). La migration des bact?ries de r?f?rences a permis de diff?rencier les bact?ries Gram positif (Cb. piscicola, Cb. divergens, Lb. curvatus, Lb. sakei et B. thermosphacta) mais aussi les bact?ries Gram n?gatif (P. phosphoreum et S. putrefaciens). Toutes les bact?ries (Cb. piscicola, Lb. curvatus et P. phosphoreum) identifi?es par culture peuvent aussi ?tre d?tect?es par TTGE. |
