Isolation of ST398 methicillin-resistant Staphylococcus aureus from pigs at abattoirs in Tohoku region, Japan.

Here, we investigated the presence of ST398 livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) in nasal swabs of 420 slaughtered pigs from 84 farms at three abattoirs in Tohoku, Japan. MRSA were isolated from 13 (3.1%) samples from 9 (10.7%) farms at two abattoirs. All isolates were classified as ST398 and were resistant to ampicillin and tetracycline. Ten and three isolates were classified as Staphylococcal Cassette Chromosome mec (SCCmec) types V and IVa, respectively. All type V isolates possessed czrC. The minimum inhibitory concentrations (MICs) of zinc chloride against types IVa and V were 1 and 4 mM, respectively. This study shows the presence of ST398 MRSA in pigs in this region. Antimicrobials and zinc compounds in feed and drugs might select SCCmec type V ST398 MRSA.