Genotypic and phenotypic characterization of Enterococcus faecalis isolates from periprosthetic joint infections

Over 2.5 million prosthetic joint implantation surgeries occur annually in the United States. Periprosthetic joint infections (PJIs), though occurring in only 1-2% of patients receiving replacement joints, are challenging to diagnose and treat and are associated with significant morbidity. The Gram-positive bacterium Enterococcus faecalis, which can be highly antibiotic resistant and is a robust biofilm producer on indwelling medical devices, accounts for 2-11% of PJIs. E. faecalis PJIs are understudied compared to those caused by other pathogens, such as Staphylococcus aureus. This motivates the need to generate a comprehensive understanding of E. faecalis PJIs to guide future treatments for these infections. To address this, we describe a panel of E. faecalis strains isolated from the surface of prosthetic joints in a cohort of individuals treated at Mayo Clinic in Rochester, MN. Here, we present the first complete genome assemblage of E. faecalis PJI isolates. Comparative genomics shows differences in genome size, virulence factors, antimicrobial resistance genes, plasmids, and prophages, underscoring the genetic diversity of these strains. These isolates have strain-specific differences in in vitro biofilm biomass, biofilm burden, and biofilm morphology. We measured robust changes in biofilm architecture and aggregation for all isolates when grown in simulated synovial fluid (SSF). Lastly, we evaluated antibiotic efficacy of these isolates and found strain specific changes across all strains when grown in SSF. Results of this study highlight the existence of genetic and phenotypic heterogeneity among E. faecalis PJI isolates which will provide valuable insight and resources for future E. faecalis PJI research.