Antibiotic resistance in early periprosthetic joint infection.

BACKGROUND: Prophylactic antibiotics significantly reduce prosthetic joint infection (PJI) rates after hip and knee arthroplasty. However, rising antibiotic resistance has raised concerns over the adequacy of conventional prophylaxis. This study aimed to identify organisms causing PJIs in hip and knee arthroplasty secondary to perioperative contamination and their susceptibility to current prophylactic antibiotics.

METHODS: We performed a retrospective 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 definition, and patients were followed-up for 2 years. For patients with confirmed PJIs, causative bacteria and their antibiotic susceptibilities were identified.

RESULTS: Thirty-five PJI cases were identified (13 hips and 22 knees). The overall definite PJI rate was 0.87% (0.7% for hips, 1.0% for knees). Ninety-six percent of patients with PJI received cefazolin prophylaxis. Culture information was available for 30 cases. The most common infecting organisms were coagulase-negative staphylococci (CoNS), causing 35% of infections. Ninety-two percent of CoNS strains were cefazolin-resistant. Twenty-five percent of patients were infected with Staphylococcus aureus, 9.1% of which were methicillin-resistant. Overall, 53% of infecting organisms were cefazolin-resistant.

CONCLUSIONS: The majority of bacteria causing early PJI are resistant to cefazolin. Whilst many organisms cultured were susceptible to vancomycin, there is currently insufficient evidence to justify its routine use as a prophylactic. However, when treating PJI in the early postoperative period, surgeons should be aware that most organisms will be methicillin-resistant, and the choice of empirical antibiotic treatment should reflect this.