Intra-familial transmission of Streptococcus dysgalactiae subsp. equisimilis (SDSE): A first case report and review of the literature

Abstract

Background: Concern about Streptococcus dysgalactiae infections has been increasing worldwide, and many cases of invasive infections have been reported. Streptococcus dysgalactiae has two main subspecies: S. dysgalactiae subsp. equisimilis (SDSE) and S. dysgalactiae subsp. dysgalactiae (SDSD). The epidemiology of invasive SDSE infections is not well understood, and the exact numbers of human SDSE infections are not known because standard laboratories are not able to identify Lancefield group C streptococci (GCS) or group G streptococci (GGS) to the species level. SDSE is often present in skin lesions, and sites of SDSE colonization and focal SDSE infections serve as the principal reservoirs for the transmission of skin and soft-tissue infections. Although the person-to-person transmission of S. pyogenes infections has been reported, the intra-familial transmission of SDSE has not been reported.

Case presentation: We report two cases of cellulitis with bacteremia in a family. A 72-year-old female with cellulitis in her right lower extremity was hospitalized, and a 104-year-old male relative was hospitalized with cellulitis 2 days later. Two strains of Streptococcus dysgalactiae subsp. equisimilis were isolated from the blood of the patients. Single nucleotide polymorphism analysis of the bacterial genomes suggested that the two strains had the same origin. This is the first case report about the intra-familial transmission of Streptococcus dysgalactiae subsp. equisimilis.

Conclusions: This is the first case report about the intra-familial transmission of Streptococcus dysgalactiae subsp. equisimilis.

Keywords: Bacteremia; Intra-familial transmission; Streptococcus dysgalactiae subsp. equisimilis (SDSE); Whole-genome sequencing.