Prevalence of Listeria Species in Raw Milk in Isfahan, Iran

Listeria monocytogenes is an important psychrotrophic foodborne pathogen which may exist in milk and dairy products. The bacterium causes listeriosis with severe clinical consequences such as meningitis, septicemia and abortion. Therefore, contamination of food stuff implies a significant health risk for human. There are a minimum data on raw milk contamination of Listeria species In Iran. Thus, the objective of this study was to assess the prevalence of Listeria spp. in raw milk in Isfahan, Iran. A total of 91 samples of raw milk were examined for the presence of Listeria spp. using a two-step selective enrichment recommended by USDA. All isolates were subjected to standard biochemical test. L. monocytogenes strains were further confirmed by PCR amplification. Of the 91 raw milk samples collected, Listeria species were isolated on five (%5.49) samples. Four (%4.39) of these five isolates identified as L. monocytogenes and one (%1.09) as L. seeligeri. All strains of L. monocytogenes identified by biochemical tests, were also confirmed by PCR. The study shows the prevalence of L. monocytogenes in raw milk sold in the market. Consumption of raw milk with mild heat treatment or its usage in traditional dishes is a common practice in Iran. Therefore, the lack of appropriate control measures could pose serious health problems. The lack of knowledge on the risks of listeriosis transmission indicating the need of implementation of food safety education program. In addition, the Iranian food safety authorities urgently should set up an effective standard to screen all susceptible food for the presence of Listeria.