High failure rate in <i>Pseudomonas aeruginosa</i> -associated periprosthetic hip and knee joint infections

<b>Introduction</b>: <i>Pseudomonas aeruginosa</i> is one of the most common Gram-negative (GN) pathogens in periprosthetic joint infections (PJIs). However, not many data are available on them. This study aimed to evaluate the prevalence of <i>P. aeruginosa</i> in hip and knee PJIs, patient characteristics, types of infection, resistance patterns, treatments, and outcomes. <b>Methods</b>: We retrospectively analyzed culture-positive revision total hip and knee arthroplasties (rTHA and rTKA) from 2008 to 2023. Cases were evaluated according to the International Consensus Meeting (ICM) 2018 and European Bone and Joint Infection Society (EBJIS) criteria 2021. The success rate was calculated according to Tier classification. <b>Results</b>: Among 1640 revision procedures performed on 1286 patients, 195 revisions in 160 patients were positive for GN microorganisms, including 50 <i>P. aeruginosa</i> cases (3.1 %, hip/knee: 39/11) in 38 patients. Most were chronic (64 %), monomicrobial (74 %) infections, particularly infected rTHA (63.8 %). <i>Proteus mirabilis</i> was the main co-pathogen (23.1 %) in polymicrobial infections. The mean follow-up time was 65.4 months. The most frequent surgical intervention was two-stage exchange (48 %). Chronic infections required significantly more total revisions than acute cases. Success rates decreased with each additional revision. Antibiotic resistance developed in three patients during subsequent revisions. The overall success rate was 46 %. Reinfection-free survival decreased from 95 % at 12 months to 22.4 % after 10 years. <b>Conclusion</b>: In our patient cohort, <i>Pseudomonas aeruginosa</i> accounted for one-third of hip and knee GN PJIs, was mostly found in infected rTHA, and was monomicrobial. Changes in antimicrobial resistance, high failure rates, and low long-term infection-free survival underline that <i>Pseudomonas aeruginosa</i> is a challenging PJI pathogen.