Species identification of β-hemolytic streptococci from diseased companion animals and their antimicrobial resistance patterns in Japan (2021)

[Abstract] We aimed to identify species and evaluate antimicrobial resistance (AMR) of β-hemolytic streptococci recovered from Japanese companion animals in 2021. Strains were recovered from clinical specimens of 109 companion animals that exhibited symptoms/signs between April and May, 2021. We identified strains by 16S rRNA sequencing and evaluated their AMR phenotypes using the broth microdilution method. Macrolide/lincosamide/tetracycline resistance genes, including erm(A), erm(B), and mef(A), in addition to tet(M), tet(O), tet(K), tet(L), and tet(S), were amplified by polymerase chain reaction. The 16S rRNA sequencing identified β-hemolytic streptococcal strains as Streptococcus canis (n=102, 93.6%), S.dysgalactiae subsp. equisimilis (n=4), S.agalactiae (n=2), and S.dysgalactiae subsp. dysgalactiae (n=1). Overall AMR rates were 34.9% for minocycline, 22.0% for erythromycin, 22.9% for azithromycin, 21.1% for clindamycin, and 10.1% for levofloxacin. We found macrolide/lincosamide/tetracycline resistance gene detection of tet(M) (9.2%), tet(O) (26.6%), tet(L) (1.8%), erm(B) (22.0%), and mef(A) (1.8%). Our findings support the unique features of β-hemolytic streptococci from companion animals (dominant S.canis isolation and dominant resistance to tetracycline), along with dominant tetracycline resistance genes, in agreement with those of β-hemolytic streptococci in 2017.