MICROBIOLOGY OF PERIPROSTHETIC JOINT INFECTION IN TOTAL HIP ARTHROPLASTY: IS ORGANISM PROFILE CHANGING ACROSS THE UNITED STATES AND EUROPE?

Introduction & Aim Regional differences in microbiology and antibiotic resistance in periprosthetic joint infection (PJI) may influence treatment, but direct comparisons of causative organisms between the United States (US) and Europe are limited. This study aimed to evaluate patients undergoing revision total hip arthroplasty (THA) for PJI in order to compare causative organism distribution and antibiotic resistance patterns as well as to evaluate any temporal trends (from 2013-2025) in organism profile between sites in the United States and Europe. Methods This retrospective cohort study included 1,535 patients from 6 distinct high volume PJI referral centers, 4 of which were in the US (n = 824) and 2 of which were in Europe (n = 711). Baseline characteristics, intraoperative culture results, and antibiotic resistance patterns were collected. Patients were grouped by region (US vs Europe) for comparison. The US cohort was younger (median: 65 vs 71 years, p<0.001), had higher body mass index (BMI) (median: 30.2 vs 27.5 kg/m2, p<0.001), and higher Charlson comorbidity index (CCI) (median: 4.0 vs 2.8, p<0.001). Results Organism distribution differed significantly between regions. The US had higher rates of culture negative (47% vs. 10%, p<0.001) and Staphylococcus aureus (15% vs. 8%, p<0.001) infections compared to Europe. Europe had higher rates of coagulase-negative Staphylococcus infections (46% vs. 9%, p<0.001) compared to the US. Europe also had a higher incidence of polymicrobial infection (15% vs. 10%, p<0.001) and anaerobic infections (9% vs. 3%, p<0.001). In contrast, Streptococcus infections were more frequent in the US (6% vs. 3%, p=0.030). Gram-negative (6% vs. 5%, p=0.393), fungal (1% vs. 1%, p=0.525), Enterococcus (2% vs. 1%, p=0.382), mycobacterial (0% vs. 0%, p=0.502), and other organisms (1% vs. 1%, p=0.978) did not differ significantly between regions. Methicillin-resistant Staphylococcus aureus was more common in the US (5% vs. 1%, p<0.001), while methicillin-resistant coagulase-negative Staphylococcus did not differ between regions (3% vs. 3%, p=0.907). Temporal trends of Staphylococcus aureus isolates remained stable over time in both regions (US: r=0.113, p=0.726; Europe: r=−0.224, p=0.463). In contrast, methicillin-resistant Staphylococcal isolates significantly declined over time, in Europe (r=−0.751, p=0.003) but not in the US (r=−0.490, p=0.106). Conclusions Organism profiles of PJI after THA demonstrate clear geographic variation. In our study there was a higher methicillin-resistance and culture negative incidence in the US, versus more frequent polymicrobial and coagulase-negative infections in Europe. Despite microbiology not changing significantly over time, the distinct profiles between regions reinforces the need for tailored diagnostic, surgical and antibiotic strategies.