Streptococcus pyogenes emm and T types within a decade, 1996-2005: implications for epidemiology and future vaccines.

Streptococcus pyogenes group A (GAS) is a primary human pathogen. We performed genetic emm sequence and serological T-antigen typing of 819 mostly invasive GAS isolates recovered in Israel during 1996-2005. Of the 72 emm types found, the six most prevalent types (1, 81, 89, 14, 28, 5) comprised 30.2% of all isolates, and emm-type changes were observed over the years. The predicted coverage of the 26-valent S. pyogenes vaccine formulated for usage in the USA was predicted to be only approximately 60%. On the basis of different emm-T antigen type associations, some Israeli strains are probably different clonal types than those found in USA. About 2% of GAS had emm types that were originally associated with S. dysgalactiae subsp. equisimilis emm genes. Therefore, routine emm typing allows meaningful GAS strain surveillance, and provides data relevant to better vaccine coverage.