Prevalence of foodborne pathogens in open markets and supermarkets in Thailand

This study was conducted in Thailand (Bangkok and Pathum Thani provinces), from June 2006 to July 2007, in order to assess the prevalence of Listeria monocytogenes, Escherichia coli O157, Salmonella, Shigella and Vibrio parahaemolyticus in foods. Retail raw meats and seafood, including chicken (n = 109), pork (n = 80), beef (n = 108), shrimp (n = 43) and oysters (n = 48), from open markets and supermarkets were analyzed. Salmonella was found in 22 of 61 (36%) open market samples (48% of chicken, none of pork and beef, and 53% of shrimp) and in 12 of 75 (16%) samples from supermarkets (57%, 12%, 24%, 0% respectively). However, a small number of L. monocytogenes were isolated, where 6 of 217 (3%) were samples from open markets (6% of chicken and 3% of pork) and 17 of 171 (10%) were from supermarkets (3% of beef, 4% of chicken, and 32% of pork). In both markets, L. monocytogenes was not detected from shrimps, neither from oysters. E. coli O157, Shigella and tdh-positive V. parahaemolyticus were not isolated in this collection. Several Salmonella and L. monocytogenes isolates were multidrug-resistant. Both markets would need better assessment, since multidrug-resistant strains have been isolated and they may lead to therapeutic failure.