Incidence de Listeria spp. et autres bactéries psychrotrophes dans le lait cru bovin dans le Nord Est Algérien

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In this study a total of 104 milk samples collected from 60 dairy cattle in six farms in the North East part of Algeria were examined for the presence of Listeria spp. and other psychrotrophic bacteria. The isolation was accomplished by cold storage of milk samples followed by plating on blood agar added of Cefazoline. The isolates were identified phenotypicaly by studying cultural, morphological, biochemical criteria; and genotypicaly using the 16S rRNA gene. Psychrotrophic bacteria from numerous genera have been isolated, both gram negative “Acinetobacter spp., Aeromonas spp., Pseudomonas spp., Stenotrophomonas spp., Proteus spp., Yersinia spp., Klebsiella spp., Alcaligenes spp., and Flavobacterium spp.” and gram positive “Enterococcus spp., Listeria spp., Staphylococcus spp., and Bacillus spp.”. Enterococcus spp. was the dominant genera in different seasons. Milk contamination by Listeria spp. was seasonal, its incidence was positive in winter and in spring, however it was absent in summer and autumn.