Microbiologic features of prosthetic joint infections at a tertiary referral orthopaedic unit.

Background: Prosthetic joint infections (PJI) are a potential devasting consequence of arthroplasty surgery. Knowledge of the causative organism and antimicrobial sensitivity increases eradication success rates for PJI.

Aims: This study aimed to: 1) Observe the PJI microbiome at a tertiary referral arthroplasty unit; 2) Make comparison to similar published observations; and; 3) Establish empiric local antibiotic PJI guidelines.

Methods: All patients with positive tissue cultures for PJIs over a 4 year period were included. An electronic microbiology laboratory database search was performed to identify isolated microorganisms, sensitivities and resistances. Time from index procedure to PJI onset was recorded. The identified PJI microbiome was compared to current literature.

Results: 86 patients involving 88 joints were included. 56% (n = 49) related to hip, 42% (n = 37) to knee and 2% (2) to shoulder arthroplasty procedures. Coagulase Negative Staphylococci (CoNS) were isolated in 32% of cases, Staphylococcus aureus (SA) in 23%, Enterococcus species and Streptococcus species in 9.0%. 19% of case occurred within 3 months of index surgery, 17% from 3-12 months and 64% after 12 months. The microbiome identified varied comparable studies.

Conclusion: This study describes a local PJI microbiome with contrasting results from comparable studies. Empiric antibiotic guidelines have been established to target treatment and a local PJI register has since been established to improve patient outcomes and antimicrobial stewardship in an era of antibiotic resistance.