Early Infection Following Arthroplasty – Are Patients Protected?

OBJECTIVE: Prophylactic antibiotics significantly reduce prosthetic joint infection (PJI) rates after hip and knee arthroplasty. However, the rise of antibiotic resistance has raised concern over the adequacy of conventional prophylaxis. This study aimed to identify organisms causing early PJI in hip and knee arthroplasties and their sensitivity to current prophylactic antibiotics. METHOD: We performed a multicentre audit of 4009 primary hip and knee arthroplasties (1852 hips and 2157 knees) at three tertiary referral hospitals. PJIs were identified according to the Infectious Diseases Society of America (IDSA) definition and all patients were followed for two years. For patients with confirmed PJIs, causative bacteria and their antibiotic sensitivities were identified. RESULTS: Thirty-five PJI cases in total were identified in the follow-up period of two years, consisting of 13 hips and 22 knees. The overall definite prosthetic joint infection rate was 0.87% (0.7% for hips, 1.0% for knees). 51.4% of PJIs occurred within the first 6 weeks, 62.9% within the first 3 months and 82.9% during the first year. Ninety-six percent (96%) of patients were given cefazolin as prophylaxis. Thirty-four percent (34%) of patients were infected with Coagulase-negative staphylococci, which were the most common infective organisms. 91.7% of these organisms were resistant to cefazolin. Twenty-five percent (25%) of patients were infected with Staphylococcus aureus, 9.1% of which were methicillin resistant. Overall, 58% of organisms were resistant to cefazolin. Sixty percent (60%) of patients who were treated with cefazolin and had available sensitivities for infective organism(s) were infected with cefazolin-resistant organisms. CONCLUSIONS: The majority of bacteria causing early PJI are resistant to the antibiotic prophylaxis given at the time of surgery. Whilst all the organisms cultured were sensitive to vancomycin, concerns regarding antibiotic stewardship remain and there is insufficient evidence to justify its routine use. However, the choice of empiric antibiotic when treating PJI in the early post-operative period should take into account resistance profiles.