A Japanese trial to monitor methicillin-resistant Staphylococcus aureus (MRSA) in imported swine during the quarantine period.

Objectives: This study aimed to determine the prevalence of methicillin-resistant Staphylococcus aureus (MRSA) in imported swine during the quarantine period in Japan.

Methods: Nasal swabs from a total of 125 swine belonging to 15 lots (unit of import) from five countries were investigated for MRSA from July 2016 to February 2017. Two isolates per positive lot were chosen for multilocus sequence typing (MLST). PCR was performed to determine the presence of the czrC gene, and antimicrobial susceptibility testing was performed by the broth dilution method.

Results: MRSA isolates were obtained from six lots (41 heads; 32.8%) from two countries. All 12 isolates that underwent MLST (two per positive lot) were classified as ST398, harboured the czrC gene and were resistant to ampicillin and tetracycline; some isolates showed additional resistance to erythromycin or streptomycin, but resistance to ciprofloxacin, gentamicin or chloramphenicol was not observed.

Conclusions: MRSA ST398 isolates were obtained from imported swine in this first trial to monitor MRSA during the quarantine period in Japan. For the 'One Health' approach against antimicrobial resistance, monitoring imported animals and generating feedback data would be important.