A comprehensive analysis of antimicrobial resistance of clinical emm89 Streptococcus pyogenes in Japan.

OBJECTIVES: Streptococcus pyogenes is involved in a wide range of diseases, including pharyngitis and life-threatening invasive infections. Increasing prevalence of antimicrobial resistance (AMR) has been reported worldwide in various bacteria, limiting the use of antibiotics in infection cases. The present study investigated the AMR of most prevalent S. pyogenes emm types, including emm89 strains in Japan. METHODS: A total of 368 previously identified S. pyogenes isolates (311 emm89 strains and 57 of other emm types), which were previously isolated from patients with invasive and non-invasive infections throughout Japan, were used in the analyses. The minimum inhibitory concentrations of seven antibiotics, including penicillin-G, azithromycin (AZM) and clindamycin, were determined, and whole-genome sequences of AMR-associated genes were screened. RESULTS: We identified 47 resistant strains, of which 91.49% (43/47) were resistant to AZM and/or clindamycin. A strong correlation was observed between non-invasive phenotypes and AMR. Whole-genome analysis indicated the wide distribution of three AMR-related genes, ermT, folP and lmrP, among the emm89 strains. Additionally, tetO was detected in tetracycline-resistance and soxS and mel was detected in chloramphenicol-resistance only in emm4 strains. CONCLUSIONS: The high prevalence of S. pyogenes resistance to AZM and/or clindamycin poses a threat to public health in Japan; thus, the development of next-generation antimicrobial therapies is imperative.