Listeria monocytogenes Contamination in Unpasteurized Traditional Cheese Products in Qazvin, Iran

Background and purpose: Listeria monocytogenes is a foodborne pathogen and a pothential risk to public health. Listeriosis is one of the most serious infectious diseases in most developed countries. Consumption of raw milk and unpasteurized traditional dairy products such as cheese can be a major reason for listeriosis in humans. This reaserch aimed at investigating Listeria monocytogenes contamination in unpasteurized cheese products by using culture and Polymerase Chain Reaction (PCR) in Qazvin, Iran. Materials and methods: In this research, 128 samples of traditional cheese products were collected from different traditional shopping centers in Qazvin, between October 2017 and September 2018. They were transported to the laboratory under controlled conditions. All isolates were analysed to biochemical test. L. monocytogenes strains were further confirmed by PCR amplification. Results: Findings showed that 14 samples (10.9%) were contaminated with L. monocytogenes. The highest prevalence of L. monocytogenes was found in white cheese samples (7%). The highest rate of contamination was reported in spring and winter (3.1%). Conclusion: Listeria contamination in cheese samples studied can pose a serious risk to consumers of non-pasteurized dairy products. Therefore, food safety and health practitioners should apply effective methods and standards.