Is there a difference in treatment outcome for monomicrobial and polymicrobial periprosthetic joint infections? Systematic review and study quality analysis

To perform a systematic review comparing the functional and objective outcomes for periprosthetic joint infection (PJI) caused by a single organism versus polymicrobial PJI. A systematic review of the treatments, as well as functional and objective outcomes of clinical studies comparing single organism and polymicrobial PJI was performed, with a mean follow up of at least 24 months and minimum level of evidence of III. Following review of the literature, a quantitative comparison between success/failure rates after the treatment of monomicrobial vs polymicrobial PJI was performed. The methodological quality of each study was assessed using a modified version of the Coleman methodology score (mCMS). The systematic search identified 6 studies, including 1075 patients (829 in the single organism group and 246 in the polymicrobial group). All the studies were case control studies. Definitions for success and treatment failure were heterogeneous. The mean success rate for any treatment of monomicrobial infection was 70.4% (range, 64.7–87.5%) and 58.4% (range, 27.8–85.7%) for polymicrobial infections, respectively (p = 0.29). The mean survivorship for treated monomicrobial and polymicrobial PJI were 69.4% (range, 66–72.8%) and 58% (52–63.8%). Quantitative analysis demonstrated that although polymicrobial infections have been identified as a risk factor for failure after a PJI, they did not result in significantly worse outcomes after treatment. Though not statistically significant, polymicrobial PJI with gram negative organisms typically resulted in poorer outcomes as compared to PJI with gram positive organisms. Antibiotic coverage should be evaluated to ensure proper coverage of such gram-negative organisms. Systematic Review of Level III Studies.