Quantification and rep-PCR characterization of Salmonella spp. in retail meats and hospital patients in Northern Thailand

Human salmonellosis is a major public health problem worldwide. Infections can pass to humans by contact with contaminated substances in the food chain. This study aimed to determine the prevalence and contamination levels of Salmonella isolated from pork, chicken and beef sold in different types of retail stores in Chiang Mai and Lamphun provinces and to investigate the genetic relatedness among Salmonella isolates in food chains in that area. A total of 360 meat samples from supermarkets, mini-grocery stores and fresh markets were obtained. Salmonella Rissen and S. Weltevreden were found in all meat sample types and in human cases. The overall prevalence of Salmonella in the chicken, pork and beef samples was 34.17%, 32.50% and 3.33%, respectively. Quantitatively, Salmonella contamination was highest in pork (1.24 log_{10} MPN/g), followed by chicken (1.08 log_{10} MPN/g), and beef (0.75 log_{10} MPN/g). The highest frequency of Salmonella contamination was found at the fresh markets (85.71%), whereas the highest quantity of contamination level was from mini-grocery stores (1.27 log_{10} MPN/g). The rep-PCR analysis results revealed that some of the Salmonella from meat samples and human cases were identical clones.