Intravenous fosfomycin for treatment of severe infections caused by carbapenem-resistant Acinetobacter baumannii: a multicenter clinical experience

Background severe infections caused by carbapenem-resistant Acinetobacter baumannii (CRAB) have been increasingly reported over the past few years. Many in vivo and in vitro studies suggest a possible role of intravenous fosfomycin for the treatment of CRAB infections. Methods this multicenter, retrospective study included patients treated with intravenous fosfomycin for severe infections caused by CRAB admitted consecutively from December 2017 to December 2022 in four Hospitals in Italy. The primary goal of the study was to evaluate the risk factors associated with 30-day mortality in the study population. A propensity score matched analysis was added to the model. Results during the study period, 102 patients with severe infection caused by CRAB treated with an intravenous fosfomycin-containing regimen were enrolled: ventilator-associated pneumonia (VAP) was diagnosed in 59% of patients, primary bacteremia in 22%, and CVC-related infection in 16%. All patients were treated with a regimen containing intravenous fosfomycin, mainly in combination with cefiderocol (n=54), colistin (n=48), and ampicillin/sulbactam (n=18). Forty-eight (47%) patients died within 30 days. Fifty-eight (57%) patients experienced a clinical therapeutic failure. Cox regression analysis showed that diabetes, primary bacteraemia, and a colistin-containing regimen were independently associated with 30-day mortality, whereas an adequate source control of infection, an early 24 h active in vitro therapy, and a cefiderocol-containing regimen were associated with survival. A colistin-based regimen, A. baumannii colonization and primary bacteremia were independently associated with clinical failure. Conversely, an adequate source control of infection, a cefiderocol-containing regimen, and an early 24 h active in vitro therapy were associated with clinical success. Conclusions Our data showed different antibiotic regimens containing fosfomycin in combination treatment of severe infections caused by CRAB.