Identification of Listeria monocytogenes from milk by cultured and PCR gene actA

Foodstuffs are exposed to microbial contamination in different ways. Also، many pathogenic microbes are transferred to human beings thorough food. Listeria monocytogenes is a pathogenic microbe which is transferred to man via foods such as raw milk, vegetables especially cabbage. It can cause diseases involving meningitis, conjunctivitis, septicemia, mastitis and abortion. Regarding different reports on contamination of milk and its products by listeria monocytogenes in developing countries involving Iran، this study tries to examine contamination of milk and its products to this bacterium in Qom province.
Different studies have proved the presence of pathogenic genes in listeria monocytogenes including actA، prF، plcA، plcB، hlyA and mpl. Because this bacterium has actin polymerization ability، it is able to move intracellularly and intercellularly، escape phagolysosome، resist humoral immune defense and eventually replicate in the host cell. actA protein is very important in controlling the interaction of actin filaments in peripheral cytoplasm of the host cell and causes the mobility of listeria monocytogenes. This study examines 100 samples including 100 raw milk samples by the isolation and molecular characterization of listeria monocytogenes.
By enrichment and culture methods in selective agar plates، biochemical methods، serological confirmation and eventually by using CHORM agar and molecular confirmation based on actA genes، %3 of listeria monocytogenes contamination was confirmed and the presence of these genes was identified in this isolated strains Key words: listeria monocytogenes. actA gene، PCR، culture method.