Emergence and spread of a new clone of M type 1 group A Streptococcus coincident with the increase in invasive diseases in Japan

Background, In Japan invasive group A streptococcal infections such as seps is and toxic shock syndrome (TSS) have increased since 1992. As is the case in the United States and Europe, M1 serotype is predominant among the isol ates from Japanese patients. Methods. By restriction enzyme digestion and pulsed field gel electrophores is, we investigated the whole genomic DNA profiles of 95 M type 1 group A s treptococcal strains isolated from patients with serious diseases including sepsis, toxic shock syndrome, necrotizing fasciitis and nonsuppurative com plications and with uncomplicated pharyngitis during 1979 through 1996 in J apan. Results. The genome profiles among 8 of 10 isolates from patients with seri ous diseases in 1979 through 1991 were all the same and were shared by the profiles of the 35 of 48 isolates from patients with uncomplicated pharyngi tis in 1982 through 1991. All 18 strains isolated from patients with invasi ve diseases in 1992 to 1996 had a unique profile, which was shared by the p rofiles of 18 of 19 isolates from uncomplicated pharyngitis during the same period. This genomic profile was distinct from the predominant or any othe r profiles before 1992, and it was found to be a new clone. Conclusions. The emergence and spread of this new clone of M type 1 Strepto coccus after 1991 may be associated with the increase in invasive streptoco ccal infections that occurred during the same period in Japan. Genomic prof iles as well as serotypes of streptococcal isolates are important for the e pidemiology of clinical relevance in streptococcal diseases.