Methicillin-resistant Staphylococcus aureus (MRSA), prevalence and importance from a food hygiene perspective

Methicillin-resistant Staphylococcus aureus (MRSA) is a significant cause ofnosocomial and community acquired infections which are difficult to treat.Furthermore, MRSA has recently been reported to colonize and causeinfections in domestic pets and food production animals. One specific clone(ST398) has been found with high prevalence, especially in pigs. As severalhuman cases have already been traced back to colonized animals, an infectionwith MRSA may today be considered as a zoonosis. A joint study of the BfRand authorities of two federal states in Germany revealed the prevalence ofMRSA in healthy pigs at slaughter, too.This paper addresses the question via which routes and with which probabilityconsumers can be colonized with animal related MRSA. Pig farmers,veterinarians, and abattoir workers dealing with pigs have an increased risk ofexposure to animal related MRSA than other people. It is obvious that MRSA isan occupational hazard for this group of people. Food production andprocessing have to be considered as one potential exposure route of MRSA forthe consumer. Contamination of meat with MRSA is likely to occur at variousstages of the processing chain, either by carry over from colonized body sites tothe carcass, by cross contamination, through the environment of processingfacilities or by people involved in the handling of carcasses or meat. A recentstudy from the Netherlands found MRSA in small quantities in about 11 % of1300 samples of several raw meat products, e.g. turkey, chicken, veal and pork.Due to lacking information on e.g. dose-response, prevalence and quantity ofMRSA in meat and commodities a valid assessment of the consumers risk iscurrently not feasible. Up to now, there is no evidence that MRSA ST398 isspread via the food chain. However, animal products remain a potential sourceof MRSA. More research is needed to quantify the risk of colonization ofconsumers with MRSA via the food chain.