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

Prosthetic joint infection (PJI) is an increasing concern for the medical profession due to rising numbers of arthroplasty surgery and thereby increasing costs of PJI. Streptococcal PJI constitutes approximately 10% of PJIs, but still the genetic features and characteristics of streptococcal PJIs are largely unexplored. Whether some sequence types (ST) dominate, certain virulence-associated genes are overrepresented and antimicrobial resistance (AMR) rates are all poorly studied. Whole-genome sequencing of Streptococcus dysgalactiae (n=22), Streptococcus agalactiae (n=10) and S. pyogenes (n=1) provided genomic data of 33 beta-haemolytic streptococci isolated from PJIs in Region Orebro county, Sweden. Relatedness was inferred based on single nucleotide polymorphisms (SNPs) in S. dysgalactiae and S. agalactiae. The genomic data was screened for virulence-associated genes available in the VFDB database. All isolates were screening for both pheno-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, AMR was more frequently observed in S. agalactiae. In conclusion, 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.