BACTERIA-SPECIFIC MORTALITY AFTER REVISION FOR PROSTHETIC JOINT INFECTION: A NATIONWIDE COHORT STUDY OF 2,455 HIP AND KNEE REVISIONS

Background Periprosthetic joint infection (PJI) following total hip and knee arthroplasty (THA and TKA) is a serious complication which is associated with increased mortality. Using a large nationwide cohort, we assessed the mortality risk according to the bacterial pathogens identified at the time of the first PJI revision. Methods Data were obtained from the Danish Hip and Knee Arthroplasty Register and the Danish Microbiology Database. We included all pathogens isolated from first-time hip and knee revisions for infection between January 1, 2010, and November 9, 2023. Mortality risk was calculated using adjusted hazard ratios (HR) with 95% confidence intervals (CI) in time to event analysis and Kaplan-Meier methodology. Being the most common pathogen in the cohort, Staphylococcus aureus served as the reference for HR calculations. Measured confounding was addressed using inverse probability of treatment weighting (IPTW) based on propensity scores, adjusting for sex, age, weight, Charlson Comorbidity Index, joint and marital status. The PJI was defined as monomicrobial when only one causative bacterium was identified. If two or more distinct bacteria were isolated from the samples, the revision was defined as a polymicrobial PJI. We identified a total of 2,453 revisions for hip and knee PJI; 63.6% following THA and 36.4% following TKA. The mean follow-up time was 7.1 years. Results The most common pathogen was S. aureus , accounting for 29% of the cases. Culture-negative infections were identified in 12% of the PJI revisions, while 24% of the PJIs were polymicrobial. Compared with S. aureus , aerobic Gram-negative bacteria were associated with increased mortality (HR 1.63, CI: 1.08 to 2.48). Among individual pathogens Escherichia coli (n=53) was associated with a higher mortality risk (HR 2.05, 95% CI 1.15–3.63), and Pseudomonas species (n=9) with the highest risk (HR 4.25, 95% CI 1.48–12.20). In contrast, Cutibacterium acnes was associated with lower mortality (HR 0.11, 95% CI 0.03–0.38). The 10-year adjusted cumulative mortality for aerobic Gram-negative bacteria was 56.8%(CI: 41 to 68.4) compared to 40%(CI: 33.8 to 45.6) for S. aureus. Conclusion The infecting pathogen causing PJI appears to be associated with all-cause mortality, with aerobic Gram-negatives having the strongest association and Cutibacterium acnes , the lowest. These findings suggest that pathogen-specific characteristics may contribute to differences in long-term outcomes following PJI and warrant further investigation.