Complete genome sequence of Streptococcus dysgalactiae subsp. equisimilis 167 carrying lancefield group C antigen and comparative genomics of S. dysgalactiae subsp. equisimilis strains

Abstract

Streptococcus dysgalactiae subsp. equisimilis (SDSE) is an emerging human pathogen that causes life-threatening invasive infections such as streptococcal toxic shock syndrome. Recent epidemiological studies reveal that invasive SDSE infections have been increasing in Asia, Europe, and the United States. Almost all SDSE carry Lance field group G or C antigen. We have determined the complete genome sequence of a human group C SDSE 167 strain. A comparison of its sequence with that of four SDSE strains, three in Lance field group G and one in Lance field group A, showedapproximately90%coverage.Most regions showing little or no homology were located in the prophages. There was no evidence of massive rearrangement in the genome of SDSE 167. Bayesian phylogeny using entire genome sequences showed that the most recent common ancestor of the five SDSE strains appeared 446 years ago. Interestingly, we found that SDSE 167 harbors sugar metabolizing enzymes in a unique region and strep to dornase in the phage region, which presumably contribute to the degradation of host tissues and the prompted cov RS mutation, respectively. A comparison of these five SDSE strains, which differ in Lance field group antigens, revealed a gene cluster presumably responsible for the synthesis of the antigenic determinant. These results may provide the basis for molecular epidemiological research of SDSE. © The Author(s) 2013.