Abstract
Streptococcus suis strains isolated from porcine endocarditis and tonsils in the Tokai area of Japan during 2004-2007 and 2014-2016 (n=114) were tested for antimicrobial susceptibility and distribution of selected resistance genes. No strains showed resistance to penicillin, ampicillin, cefotaxime, meropenem, vancomycin, and levofloxacin. High resistance to tetracycline (80.7%), clindamycin (65.8%), erythromycin (56.1%), and clarithromycin (56.1%) was observed. In chloramphenicol and sulfamethoxazole-trimethoprim, there was a trend towards increased resistance between the first (2004-2007) and second (2014-2016) periods. tet(O) and erm(B) genes were the most frequently detected, and tet(M) and mef(A/E) genes were only detected in strains isolated during 2014-2016. These results indicate that chloramphenicol and sulfamethoxazole-trimethoprim resistance, and tet(M) and mef(A/E) genes emerged in S. suis of this area after 2014.