Marziyeh Rezaei - Department of Food Science and Engineering, Baharan Higher Education Institute, Gorgan, Iran .
Morteza Khomeiri - Department of Food Science and Technology, Faculty of Food Technology, Gorgan University of Agricultural Sciences and Natural Resources, Gorgan, Iran.
Maryam Ebrahimi - Department of Food Science and Technology, Faculty of Food Technology, Gorgan University of Agricultural Sciences and Natural Resources, Gorgan, Iran.
Sonia Kiani - Department of Food Science and Engineering, Baharan Higher Education Institute, Gorgan, Iran .
Mojtaba Raeisi - Laboratory Science Research Center, Golestan University of Medical Sciences, Gorgan, Iran.

Background: 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 Escherichia coli and Listeria monocytogenes in the raw milk samples of the dairy farms in Golestan province, Iran. Methods: In total, ۱۰۰ samples were collected from dairy farms in hot and cold seasons. The frequency of E. coli and L. monocytogenes was determined using biochemical tests and polymerase chain reaction (PCR). Results: The biochemical tests indicated that ۲۸% and ۲۷% of the samples were contaminated with E. coli and L. monocytogenes based on the culture-dependent methods, respectively. In addition, ۳۵ and ۴۰ samples were contaminated with E. coli and L. monocytogenes based on PCR, respectively. PCR had higher sensitivity compared to the biochemical tests (P ˂ ۰.۰۵). E. coli and L. monocytogenes contamination was significantly higher in traditional dairy farms than industrial dairy farms (P ˂ ۰.۰۵). However, seasonal sampling and geographical region had no significant effects on the contamination load. Conclusion: According to the results, E. coli and L. monocytogenes were highly frequent in the raw milks samples. However, the microbial loads had no significant differences in hot seasons and traditional dairy farms.

Escherichia coli, Listeria monocytogenes, Raw milk, Polymerase chain reaction, Biochemical test