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.