Causative organisms in revision total hip & knee arthroplasty for infection: Increasing multi-antibiotic resistance in coagulase-negative Staphylococcus and the implications for antibiotic prophylaxis

BACKGROUND AND PURPOSE: Increasing resistance among post-operative Coagulase-negative Staphylococci (CNS) infections have been reported. We present our experience changing resistance patterns.

METHODS: We examined microbiological results from hip and knee revisions from 2001 to 2010 and compared resistance to all Staphylococcus aureus (SA) and CNS cultured from regional pan-speciality sources, in order to examine the patterns of antibiotic resistance.

MAIN FINDINGS: 72 revisions in 67 patients were included. The most common organisms were SA (36%) and CNS (35%). Resistance to methicillin was 72% for CNS versus 20% for SA and resistance to gentamicin was 40% for CNS versus 4% for SA. Among all regional (background pan-speciality) cultures SA resistance to methicillin fell from 32% to 16% from 2006 to 10 with no change in gentamicin resistance at 3%. During the same period resistance of CNS to methicillin and gentamicin increased from 63% to 70% and 32%-47% respectively.

CONCLUSIONS: Resistance of CNS to both methicillin and gentamicin is higher than with SA and appears to be increasing. At least 32% of CNS and 4% of SA from infected TKRs/THRs were resistant to our current prophylaxis regime. These changing patterns of resistance may have implications for future antibiotic prophylaxis regimes.