Genomic characterization of beta-haemolytic streptococci isolated from prosthetic joint infections.

Abstract

Prosthetic joint infection (PJI) is an increasing concern for the medical profession, as higher numbers of arthroplasty surgeries lead to rising PJI-related costs. Streptococcal PJIs constitute approximately 10% of PJIs, but their genetic features and characteristics remain largely unexplored. Little is known about antimicrobial resistance (AMR) rates, whether some sequence types (ST) dominate, and whether certain virulence-associated genes are overrepresented. We used whole-genome sequencing of Streptococcus dysgalactiae (n=22), Streptococcus agalactiae (n=10) and S.pyogenes (n=1) to elicit genomic data on 33 beta-haemolytic streptococci isolated from PJIs in Region Örebro county, Sweden. Relatedness was inferred based on single nucleotide polymorphisms in S.dysgalactiae and S.agalactiae. The genomic data were screened for virulence-associated genes available in the Virulence Factor Database. All isolates were screened for both phenotypic and genotypic resistance. The S.dysgalactiae and S.agalactiae isolates were genetically diverse, although 32% of S.dysgalactiae isolates (n=7) were ST20. The speS and PI-2A genes were less represented in these isolates among virulence-associated genes, and AMR was more frequently observed in S.agalactiae. We conclude that PJIs caused by beta-haemolytic streptococci are not dominated by genetically similar beta-haemolytic streptococci. There were distinct inter-species differences in AMR between S.agalactiae and S.dysgalactiae.