Molecular characterization of Streptococcus pyogenes isolates collected during periods of increased acute rheumatic fever activity in Utah

BACKGROUND: Salt Lake City, Utah has seen a continuing resurgence of rheumatic fever (RF) since 1985. METHODS: emm genotyping and multilocus sequence typing of streptococcal isolates from periods of increased RF activity were performed. RESULTS: Multiple genotypes were present during 1985 and 1998, two peak years of RF activity, and in 1992, a year with reduced RF activity. emm3 and emm18.1 were present in 1985 and 1998, but not in 1992. Two other emm types, 12 and L28, were significantly elevated in 1998 (a peak RF year) over 1992 (a non-peak RF year). Allelic profiles for the emm3 and emm18.1 isolates exhibited clonality. CONCLUSIONS: During years of increased RF activity multiple emm types, including emm18.1 and emm3, were circulating in the community. During a year of decreased RF activity, emm3 and emm18.1 genotypes were absent. The clonality of the emm3 and emm18.1 types suggests that specific clones of both types are important in the resurgence of RF during these peak years. Two other genotypes, emm12 and emmL28, may also be associated with the persistence of RF in the Salt Lake City, UT area.