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Gram-negative prosthetic joint infections: risk factors and outcome of treatment.

BACKGROUND
Little information is available regarding the demographic characteristics and outcomes of patients with prosthetic joint infection (PJI) resulting from gram-negative (GN) organisms, compared with patients with PJI resulting from gram-positive (GP) organisms.


METHODS
We performed a retrospective cohort analysis of all cases of PJI that were treated at our institution during the period from 2000 through 2006.


RESULTS
GN microorganisms were involved in 53 (15%) of 346 first-time episodes of PJI, and Pseudomonas aeruginosa was the most commonly isolated pathogen (21 [40%] of the 53 episodes). Patients with GN PJI were older (median age, 68 vs. 59 years; P<.001) and developed infection earlier (median joint age, 74 vs. 109 days; P<.001) than those with GP PJI. Of the 53 episodes of GN PJI, 27 (51%) were treated with debridement, 16 (30%) with 2-stage exchange arthroplasty, and 10 (19%) with resection arthroplasty. Treating GN PJI with debridement was associated with a lower 2-year cumulative probability of success than treating GP PJI with debridement (27% vs. 47% of episodes were successfully treated; P=.002); no difference was found when a PJI was treated with 2-stage exchange or resection arthroplasty. A longer duration of symptoms before treatment with debridement was associated with treatment failure for GN PJI, compared with for GP PJI (median duration of symptoms, 11 vs. 5 days; P=.02).


CONCLUSIONS
GN PJI represents a substantial proportion of all occurrences of PJI. Debridement alone has a high failure rate and should not be attempted when the duration of symptoms is long. Resection of the prosthesis, with or without subsequent reimplantation, as a result of GN PJI is associated with a favorable outcome rate that is comparable to that associated with PJI due to GP pathogens.