A Survey on the Sanitary Condition and Prevalence of Listeria monocytogenes in Commercial Refrigerators in Khuzestan Province, Iran

Background: Listeria monocytogenes can grow in a variety of foods that are stored in refrigerators. This bacterium can adhere to various surfaces and form biofilms. Given that refrigerator temperature can support bacterial growth and proliferation, increasing the number of bacteria in refrigerator spaces endangers the consumer’s health. Objective: The purpose of this study was to investigate the prevalence of L. monocytogenes and the sanitary conditions of commercial refrigerators used in food supply centers in Khuzestan province, southwest Iran. Materials and Methods: Overall, 204 swap samples were collected from the inner surfaces of various industrial refrigerators in five different zones. The samples were enriched in Listeria enrichment broth and cultured on PALCAM agar plates. Suspected colonies were identified by biochemical tests and the polymerase chain reaction. Additionally, the sanitary condition of the refrigerator, method and duration of refrigerator cleaning, last washing date, and type of the applied detergent were recorded, and the antibacterial susceptibility of the isolates was tested as well. Results: The results demonstrated that four refrigerators (1.96%) located in Ahvaz (center) and Ramhormoz (east) were contaminated with L. monocytogenes. The internal temperatures of 67% of the refrigerators were above 5 °C, and most operators used a mixture of water and a dishwasher or water alone to clean their refrigerators. In addition, 31.9% of the refrigerators were in an unfavorable cleaning condition, and 32.8% of the refrigerators were not sealed properly. The isolates were resistant to streptomycin and represented intermediate resistance to tetracycline and penicillin. Conclusion: The contamination of industrial refrigerators with antibiotic-resistant L. monocytogenes may pose a threat to public health. Authorities should increase the monitoring of industrial refrigerators and provide the necessary training for refrigerator users.