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Phenotypic and Genotypic Characterization of Carnobacterium divergens Isolated from Refrigerated Tunisian Minced Raw Beef Meat

Thouraya Mokrani, Ines Essid, Mnasser Hassouna, Lachheb Jihene, Ghram Abdeljalil, and Ahlem Jouini

Six psychotropic strains of Carnobacterium divergens were isolated from Tunisian minced raw beef meat packed and stored at 6°C. They were first identified by biochemical methods. Using biochemical reactions and carbohydrate fermentation before their characterisation by molecular techniques. The strain of Carnobacterium divergens is a nonmotile, Gram-positive psychotropic rod that lacks catalase, oxidase and mannitol. It grows at pH 9.1 (D-MRS agar), but not on acetate agar (pH ≤ 5.4). For all these isolates, the phenotypic identification, using the API 50 CHL system, revealed a variability in the fermentation abilities of some sugars (glycerol, amygdaline, arbutine, D-trehalose and potassium gluconate). Species-specific polymerase chain reaction (PCR) primers were used to ensure identification of these isolated strains at the species level. Moreover, the sequencing of 16S rRNA gene confirmed that all the six isolates are identified as C. divergens. The Rep-PCR technique was performed to investigate intra-specific diversity within these six strains of C. divergens, commonly identified in meat. The Rep-PCR method distinguished the C. divergens strains, demonstrating their biodiversity and their evident similarities. BOX and REP primers allowed amplification with 85% and 80% similarities between the strains, respectively. The BOXA1R and REP primers were proven to be useful for the differentiation of C. divergens strains.