Characteristics of Group A Streptococcus M1 and Non-M1 Isolates from Adult and Pediatric Populations in Central Japan, 2024-2025: sic Nucleotide Alleles with CovS Amino Acid Mutations in M1 Clones.

Abstract

We aimed to specify the characteristics of group A Streptococcus M1 (n = 23) or non-M1 (n = 282) isolates from adult (n = 176) and pediatric (n = 129) populations in central Japan, October 2024-April 2025. Of the 14 speA-possessing non-M1 isolates, there were seven emm3.93 isolates from 6 non-invasive samples of pediatric patients and 1 invasive specimen of an adult patient. We found the distribution of M1 clones containing M1_global (n = 1), M1_13snps (n = 4), or M1_UK (n = 18) lineages in the central Japan region consisting of Tokyo, Chiba, Tochigi, Saitama and Kanagawa. The M1 clones were from 21 non-invasive samples of pediatric/adult patients and 2 invasive specimens from adult patients. Additionally, we determined the sic nucleotide alleles and observed the M1_global/M1_13snps/M1_UK sic clustering. Of the CovS amino acid (AA) mutations among M1, there was an insertion of transposase (ISAs1-like IS1548 transposase, 377 AA) into the CovS histidine kinase-like ATPase domain (following AA position 458) of one invasive M1_UK isolate. Our observations suggest that CovS AA mutations in invasive isolates with M1_UK should be specified within the four functional domains of CovS to evaluate their hypervirulent properties.