Gram-negative prosthetic joint infections: a retrospective multicentre European study of incidence, risk factors, and treatment outcomes

Background: Gram-negative (GN) bacteria are an increasingly recognized cause of prosthetic joint infection (PJI), accounting for 10 %–20 % of cases. However, epidemiological data from European centres remain limited. This study aimed to evaluate the incidence, risk factors, microbiological profile, and treatment outcomes of GN PJI in several European tertiary referral hospitals. Methods: We conducted a retrospective multicentre study including all culture-positive hip and knee PJIs diagnosed between 2014 and 2018 at three tertiary hospitals in Italy, Spain, and Switzerland. Demographic characteristics, comorbidities, surgical management, microbiological data including antimicrobial susceptibility, and treatment outcomes were analysed. Treatment success was defined as absence of persistent or recurrent infection requiring additional surgery, prosthesis removal, infection-related mortality, or long-term suppressive antibiotic therapy. Results: Among 780 confirmed PJIs, 71 (9.1 %) were caused by GN bacteria. The most frequent pathogens were polymicrobial infections (29.6 %), Escherichia coli (25.4 %), and Pseudomonas aeruginosa (19.7 %). GN PJI mainly affected elderly patients (median age 74 years), females (60.6 %), and those with comorbidities such as diabetes mellitus (32.4 %) and those who are overweight/obese (62 %). Hip infections were more common than knee infections (59.2 % vs. 40.8 %). Overall treatment success was 89 %. Two-stage revision showed the highest success rate of 94.8 % compared with one-stage exchange (88 %) and DAIR (81 %). Ciprofloxacin was used in 72 % of cases. Conclusions: GN PJI incidence was comparable to that of previous reports. These infections occur more often in elderly patients with comorbidities. Two-stage revision remains the most effective surgical strategy, and ciprofloxacin continues to be a key component of antimicrobial therapy for susceptible GN infections.