2008 Abstract : 6

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Authors: Parvizi J, Bender B., Ghanem E, Steinbrecher J, Azzam K, Barrack R

Title: Periprosthetic Infection: Is The Organism Profile Changing?

Institution: Rothman Institute, Philadelphia, PA

Purpose: The aim of this study was to evaluate the change in type and antibiotic sensitivity of organisms causing PJI over the past few years. We hypothesized that the incidence of PJI caused by methicillin resistant organisms has been on the rise.

Methods: All patients with proven PJI who underwent surgical treatment at our institutions between 1999 and 2006 were included. There were 475 patients with a mean age of 66 years (range, 17-94 years).Patients were included only once in the analysis unless an organism was grown during a second revision procedure that was different from the one culture during the initial surgery.

Results: The burden of PJI at our institutions has increased over the last few years. Gram positive cocci cause 91% of PJI, and gram negative organisms account for most of the remaining infections (8%). A steady increase in the incidence of infections caused by methicillin resistant species was noted with the incidence for Staphylococcus aureus (MRSA) and Staphylococcus epidermidis (MRSE) increasing from 23% in 1999 to over twice that at 61% in 2006.

Discussion and Conclusion: The findings of this indicate that a change in the profile of infecting organisms resulting in PJI has occurred over the last few years, at least at our institutions. The main pathogens causing PJI currently are methicillin resistant strains. The increase in the number of infections caused by methicillin resistant organisms could potentially compromise the success of current treatment for this condition. Although liberal use of antibiotic is likely to be the major reason,future studies are needed to assess the reason behind the worrisome rise in the incidence of methicillin resistant periprosthetic infections.