Osteosynthesis-associated infection of the lower limbs by multidrug-resistant and extensively drug-resistant Gram-negative bacteria : a multicentre cohort study

Purpose: The purpose of this study was the clinical and therapeutic assessment of lower-limb osteosynthesis-associated infection (OAI) by multidrug-resistant (MDR) and extensively drug-resistant (XDR) Gram-negative bacteria (GNB), which have been poorly studied to date. Methods: A prospective multicentre observational study was conducted on behalf of ESGIAI (the European Society of Clinical Microbiology and Infectious Diseases (ESCMID) Study Group on Implant-Associated Infections). Factors associated with remission of the infection were evaluated by multivariate and Cox regression analysis for a 24-month follow-up period. Results: Patients (nCombining double low line57) had a history of trauma (87.7 %), tumour resection (7 %) and other bone lesions (5.3 %). Pathogens included Escherichia coli (nCombining double low line16), Pseudomonas aeruginosa (nCombining double low line14; XDR 50 %), Klebsiella spp. (nCombining double low line7), Enterobacter spp. (nCombining double low line9), Acinetobacter spp. (nCombining double low line5), Proteus mirabilis (nCombining double low line3), Serratia marcescens (nCombining double low line2) and Stenotrophomonas maltophilia (nCombining double low line1). The prevalence of ESBL (extended-spectrum β-lactamase), fluoroquinolone and carbapenem resistance were 71.9 %, 59.6 % and 17.5 % respectively. Most patients (nCombining double low line37; 64.9 %) were treated with a combination including carbapenems (nCombining double low line32) and colistin (nCombining double low line11) for a mean of 63.3 d. Implant retention with debridement occurred in early OAI (66.7 %), whereas the infected device was removed in late OAI (70.4 %) (pCombining double low line0.008). OAI remission was achieved in 29 cases (50.9 %). The type of surgery, antimicrobial resistance and duration of treatment did not significantly influence the outcome. Independent predictors of the failure to eradicate OAI were age >60 years (hazard ratio, HR, of 3.875; 95 % confidence interval, CI95 %, of 1.540-9.752; pCombining double low line0.004) and multiple surgeries for OAI (HR of 2.822; CI95 % of 1.144-6.963; pCombining double low line0.024). Conclusions: Only half of the MDR/XDR GNB OAI cases treated by antimicrobials and surgery had a successful outcome. Advanced age and multiple surgeries hampered the eradication of OAI. Optimal therapeutic options remain a challenge.