Polymerase chain reaction (PCR4)-based detection of hly and plc-A genes in Listeria monocytogenes isolated from dairy and meat products in Iran

Listeria monocytogenes is a ubiquitous Gram positive organism causative agent of many hazardous conditions like meningitis and sepsis. To isolate L. monocytogenes from various food samples collected from different markets in Iran and evaluate pathogenic potential of the isolates by determining two virulence associated genes (hly and plc-A) and sequencing them, a total of 130 samples including dairy and meat products were collected. Cold enrichment method was used for the isolation of Listeria monocytogenes. The isolated pathogens were identified and confirmed by biochemical and polymerase chain reaction (PCR). PCR method was done to amplify two gene fragments, a 1590 and 954 bp for hly and plc-A genes, respectively by using sequencing primers. Listeria monocytogenes was isolated from 3.1% of all samples. The bacterium was isolated 2.5% in dairy and 4% in meat samples. All isolates were hemolytic and positive for hly gene. Also 100% of isolates had plc-A gene. The results of this study indicates that consumption of ready to eat food is hazardous specially for high risk persons .Besides that, pathogenic potential of isolated strains is important because of existences of virulence gene in all of the isolates.   Key words: Listeria monocytogenes, hly and plc-A genes, polymerase chain reaction (PCR), dairy, meat.