en Microbial pathogenesis Microbial pathogenesis Original article Original article <p dir="ltr"><strong>Introduction:</strong> This study was intended to determine the presence and distribution of <em>Listeria monocytogenes</em> in various meat and dairy products from Qazvin Province by culture followed by biochemical and morphological assays. The identity of the isolates was further obtained by amplification of <em>prf</em>A gene in bacteria isolates. This gene is a transcriptional activator of virulence&nbsp;gene&nbsp;expression within the pathogenic <em>L. monocytogenes</em>. <strong>Method: </strong>In a cross-sectional design, a total of 182 different food samples were collected from different areas in Qazvin, Iran. Bacterial isolates were obtained by the cold enrichment method. DNA extraction from the pelleted cells was conducted and then <em>prfA</em> gene was amplified by conventional PCR.<strong> Results:</strong> As many as 37 (20.3%) food samples were positive for <em>Listeria </em>spp. including 21 (56.8%) <em>L. monocytogenes</em>, 7 (18.9%)<em> Listeria innocua</em>, 4 (10.8%) <em>Listeria welshimri, </em>3 (8.1%), <em>Listeria seligeri</em>, and 2 (5.4%) <em>Listeria grayi</em>. None of the isolated specimen was <em>Listeria</em><em> ivanovii</em>. The <em>PrfA</em> gene was amplified in all <em>L. monocytogenes</em> specimen. Moreover, PCR assay had high sensitivity and specificity for bacterial identification. <strong>Conclusion: </strong>To sum up, presence of<em> L. monocytogenes</em> in food samples was confirmed in this region, it was more frequent in milk specimen<span dir="RTL">.</span> In addition to common culture techniques, PCR assay showed higher sensitivity and specificity for <em>L. monocytogenes</em> detection in contaminated foods.</p> Listeria monocytogenes, PrfA, PCR, Milk, Meat 159 162 http://jommid.pasteur.ac.ir/browse.php?a_code=A-10-85-1&slc_lang=en&sid=1 Ashraf Haj Hosseini payeshmarja@yahoo.com No 1. College of Food Science and Technology, Science and Research Branch, Islamic Azad University, Tehran, Iran Anousheh Sharifan : Anousheh.sharifan123@yahoo.com Yes 2. Assistant professor. Department of Food Science and Technology, Islamic Azad University, Science and Research Branch, Tehran, Iran Akram Tabatabaee akram_tabatabaee@yahoo.com No Department of Biology, East Tehran Branch, Islamic Azad University, Tehran, Iran