Genomic characterization and outcome of Prosthetic Joint Infections caused by Staphylococcus aureus

BackgroundStaphylococcus aureus is a commensal, colonizing the skin, nares and other mucous membranes, but can also acts as a pathogen and is considered one of the leading causes of infectious disease worldwide. It is the most common microorganism in prosthetic joint infections (PJIs), and the outcome of treatment has recently been described as poor compared to that of other bacteria. The aims of the present study were to explore the genetic relatedness between commensal and invasive S. aureus strains, as well as explore bacterial and host related risk factors for failure of treatment.MethodsPatient data was retrospectively extracted from medical records. Whole-genome sequencing was performed on both S. aureus strains obtained from PJIs (n=100) as well as commensal nasal strains from a group of healthy patients awaiting arthroplasty (n=101). ResultsNo PJI specific clusters were found using core genome multilocus sequence typing (cgMLST) or MLST clonal complexes (CCs) , and the distribution of the various CCs among isolates from PJIs and nares was almost equal and highly intermingled. The prevalence of virulence genes was similar in PJI and nasal isolates except for exfoliative toxin A . Isolates from patients with favorable outcome, and those where treatment failed were genetically very similar; however presence of an antibiotic resistance phenotype, and antimicrobial treatment lacking biofilm activity were highly associated with failureConclusionsCommensal and invasive isolates of S. aureus in arthroplasty patients were genetically indistinguishable, suggesting that commensal S. aureus clones are capable of causing PJIs. Eradication and treatment failure is foremost dependent on biofilm maturation status and the presence of antibiotic resistant phenotypes.