First isolation of ST398 methicillin-resistant Staphylococcus aureus carrying staphylococcal cassette chromosome mec type IVd from pig ears in Japan

The emergence and increasing prevalence of livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) are a global concern. To investigate the prevalence and characteristics of sequence type 398 (ST398) MRSA in pig ears, 102 pig’s ears were collected from 102 animals shipped from 51 farms at an abattoir. Eight ST398 MRSA isolates were isolated from the ears of eight pigs shipped from seven farms. Of the eight ST398 isolates, seven had the staphylococcal cassette chromosome mec (SCCmec) type IVd and these were obtained from seven pigs shipped from six farms. Single nucleotide polymorphisms ranging from 13 to 26 were observed in the core-genome regions in the seven SCCmec type IVd isolates. We believe that this is the first report on the isolation of ST398 MRSA SCCmec type IVd in Japan.