Prevalence of Listeria Spp. in Raw Milk in Syria

Testing for Listeria spp. was performed in milk samples collected from Syrian provinces, from August 2005 to December 2008. A total of 766 milk samples were collected from randomly selected dairy farms. Using conventional bacteriologic methods, 84 samples (10.96%) were positive for Listeria spp. The isolated Listeria spp. strains were catalase positive, oxidase negative, did not produce H2S and were motile. The highest prevalence of Listeria spp. was found in raw bovine milk samples (16.2%), followed by sheep milk samples (12.4%), whereas Listeria spp. was not found in tested goat milk samples. L. monocytogenes was the most frequently isolated bacterium and was found in 41.6% of the raw milk samples. The remaining isolates were L. innocua (17.8%), L. ivanovii (14.2%), L. welshimeri (9.5%) and L. gravi (4.7%). PCR has confirmed our results using the specific 16S rRNA gene and 16S-23S spacer involved in the genotypic identification of Listeria sp. The results of this study indicated the potential risk of the infection with Listeria in people consuming raw and unpasteurised milk and dairy products.