en Food Safety and Hygiene Food Safety and Hygiene پژوهشي Original Article <div style="text-align: justify;"><span style="font-size:14px;"><span style="font-family:times new roman;"><strong>Background:</strong> Milk is an essential human nutrient, and the monitoring of its sanitation is vital during transportation and storage. The present study aimed to assess bacteriological contamination with <em>Escherichia coli</em> and <em>Listeria monocytogenes</em> in the raw milk samples of the dairy farms in Golestan province, Iran. <span dir="RTL"></span><br> <strong>Methods:</strong> In total, 100 samples were collected from dairy farms in hot and cold seasons. The frequency of <em>E. coli</em> and <em>L. monocytogenes</em> was determined using biochemical tests and polymerase chain reaction (PCR). <span dir="RTL"></span><br> <strong>Results:</strong> The biochemical tests indicated that 28% and 27% of the samples were contaminated with <em>E. coli</em> and <em>L. monocytogenes</em> based on the culture-dependent methods, respectively. In addition, 35 and 40 samples were contaminated with <em>E. coli</em> and <em>L. monocytogenes</em> based on PCR, respectively. PCR had higher sensitivity compared to the biochemical tests (<em>P</em> ˂ 0.05). <em>E. coli</em> and <em>L. monocytogenes</em> contamination was significantly higher in traditional dairy farms than industrial dairy farms (<em>P</em> ˂ 0.05). However, seasonal sampling and geographical region had no significant effects on the contamination load.<span dir="RTL"></span><br> <strong>Conclusion: </strong>According to the results, <em>E. coli</em> and <em>L. monocytogenes</em> were highly frequent in the raw milks samples. However, the microbial loads had no significant differences in hot seasons and traditional dairy farms.</span></span></div> Escherichia coli, Listeria monocytogenes, Raw milk, Polymerase chain reaction, Biochemical test 160 164 http://jhehp.zums.ac.ir/browse.php?a_code=A-10-78-1&slc_lang=en&sid=1 Marziyeh Rezaei m.rezaei4780@yahoo.com 10031947532846009767 10031947532846009767 No Department of Food Science and Engineering, Baharan Higher Education Institute, Gorgan, Iran . Morteza Khomeiri m.raeisi2000@gmail.com 10031947532846009768 10031947532846009768 No Department of Food Science and Technology, Faculty of Food Technology, Gorgan University of Agricultural Sciences and Natural Resources, Gorgan, Iran. Maryam Ebrahimi maryamebrahimi2003@yahoo.com 10031947532846009769 10031947532846009769 No Department of Food Science and Technology, Faculty of Food Technology, Gorgan University of Agricultural Sciences and Natural Resources, Gorgan, Iran. Sonia Kiani sonia.kiani@ymail.com 10031947532846009770 10031947532846009770 No Department of Food Science and Engineering, Baharan Higher Education Institute, Gorgan, Iran . Mojtaba Raeisi raeisi.mojtaba@yahoo.com 10031947532846009771 10031947532846009771 Yes Laboratory Science Research Center, Golestan University of Medical Sciences, Gorgan, Iran.