Genotypic characterization of Listeria monocytogenes isolated from milk and ready-to-eat indigenous milk products

Listeria monocytogenes is a food borne pathogen associated with severe diseases in humans and animals. We present the genotypic analysis of 18 L. monocytogenes isolates recovered from milk and ready-to-eat (RTE) indigenous milk products by multiplex-PCR, allowing serovar predictions, and by random amplification of polymorphic DNA (RAPD) assays. Multiplex-PCR serotyping assay revealed 72.2% (13/18) strains belonging to serovar group 4b, 4d, 4e, 22.2% (4/18) to serovar group 1/2b, 3b while 5.5% (1/18) to serovar group 1/2a, 3a. RAPD analysis revealed five RAPD profiles from eight L. monocytogenes strains from milk, and seven RAPD profiles from ten strains from milk products. Though RAPD analysis allowed discrimination among isolates of the same serotype and among isolates from the same sampling areas or those isolated from different areas, our results suggests that most of the L. monocytogenes isolates were indeed sporadically harboured by single food items. Thus, RAPD together with multiplex-PCR serotyping allowed rapid discrimination of L. monocytogenes strains and therefore could serve as an economical tool for typing L. monocytogenes strains. In addition, the predominance of L. monocytogenes serotype 4b in our study is of public health concern, as this serotype has been most frequently associated with human listeriosis.