Methicillin resistant S. aureus (MRSA) in the pork food chain in Germany
This paper gives an overview on studies carried out in Germany on the prevalence of MRSA on different stages of the pork food chain. Prevalence studies were carried out on herd level for breeding (201 herds) and fattening pigs (290 herds), at abattoirs (n=1026 pigs), in a pork processing facility and in pig meat at retail. MRSA were characterized using spa-typing, SCCmec-typing and testing for antimicrobial resistance. The highest proportion of positive samples was determined in pigs at slaughter (58% of the pigs, 98% of slaughter batches), followed by fattening herds (52%) and breeding herds (42%). MRSA in primary production was associated with larger pig herds and purchasing pigs of different origins. MRSA were isolated from all stages of the post-harvest production chain. Meat samples at retail were positive for MRSA in both years considered, namely 2008 and 2009 (8.4% and 15.8%). Most isolates were of spa-types associated with the multi-locus sequence type ST398 (t011, t034 and t108). Regional differences in the contribution of different spa-types to the overall burden of MRSA in primary production were identified. Non ST398 strains were isolated from breeding herds (7%) but not from fattening herds or slaughter pigs. However, such strains were also isolated from fresh pork. Most isolates carried SCCmec-types V, III and IVa. Antimicrobial resistance was predominantly observed for beta-lactams, tetracycline, lincosamides, and macrolides. Resistance to fluoroquinolones was present at varying levels. Resistance to vancomycin, fusidic acid and linezolid was only observed in exceptional cases. The results of the studies indicate that MRSA is widespread in pig production and that it is readily transmitted to pork via the food chain. Further studies are needed to elucidate the potential to control MRSA in primary production, at harvest and in the post harvest food chain.