Prevalence of methicillin-resistant Staphylococcus aureus in meat

Recently the isolation of methicillin-resistant Staphylococcus aureus (MRSA) strains from several food-producing animals has been reported. During slaughtering of MRSA-positive animals, contamination of carcasses with MRSA may occur and consequently the meat of these animals may get contaminated. The aim of this study was to estimate the prevalence of MRSA in raw meat samples from the retail trade. Samples of raw beef, pork, veal, lamb/mutton, chicken, turkey, fowl and game were collected from the retail trade. A detection method including a two-step enrichment in Mueller–Hinton broth + 6.5% NaCl and phenol red mannitol broth containing ceftizoxime and aztreonam, followed by isolation on MRSA ID agar (bioMérieux) was evaluated and subsequently applied for the detection of MRSA in samples of raw meats. MRSA strains were isolated from 264 (11.9%) of 2217 samples analyzed. Isolation percentages for the meat species were: beef (10.6%), veal (15.2%), lamb and mutton (6.2%), pork (10.7%), chicken (16.0%), turkey (35.3%), fowl (3.4%) and game (2.2%). The majority (85%) of the isolated strains belonged to spa-types of pulsed-field gel electrophoresis (PFGE) non-typeable (NT)-MRSA, corresponding to the multilocus sequence type ST398, a type also recently isolated in the Netherlands from pigs. However, a smaller part of these strains were found to be of other ST's, possibly of human origin. Further studies are needed to elucidate transmission routes of MRSA in relation to meat and other foods and to provide the tools for preventing the spread of MRSA. At present the high prevalence of MRSA in meat has not been shown to contribute significantly to the dissemination of MRSA to humans and the possible health hazard for consumers of the presence of MRSA in foods should be further elucidated.