Characteristics of group A <i>Streptococcus</i> M1 or non-M1 isolates from adult and pediatric populations in central Japan, 2024–2025: <i>sic</i> nucleotide alleles with CovS amino acid mutations of M1 clones

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 speA-possessing fourteen non-M1 isolates, there were seven emm3.93 isolates from six non-invasive samples of pediatric patients and one invasive specimen of an adult patient. We found the distribution of M1 clones containing M1_global (n = 1)/M1_13snps (n = 4)/M1_UK (n = 18)-lineages in central Japan of Tokyo/Chiba/Tochigi/Saitama/Kanagawa. The M1 clones were from twenty-one non-invasive samples of pediatric/adult patients and two invasive specimens of 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 CovS histidine kinase-like ATPase domain (following AA position 458) of one invasive M1_UK isolate. Our observations suggest that CovS AA mutations of invasive isolates with M1_UK should be specified within its four functional domains to evaluate their hypervirulent properties.