Efficacy of cefiderocol, a novel siderophore cephalosporin, against multi-drug resistant Acinetobacter baumannii clinical isolates in Japan

Multidrug-resistant Acinetobacter baumannii (MDRAB) is an important pathogen that causes nosocomial infections and is resistant to almost all antibiotics, including carbapenems. Cefiderocol is a novel siderophore cephalosporin that is active against a broad spectrum of Gram-negative bacteria. However, the susceptibility of MDRAB from Japan to cefiderocol has not yet been reported. In this study, we measured the minimum inhibitory concentrations (MICs) of antibiotics, including cefiderocol, against MDRAB clinical isolates collected during a nosocomial outbreak from 2009 to 2010 at Teikyo University Hospital in Japan. We found that all 10 MDRAB clinical isolates tested were susceptible to cefiderocol, with an MIC range of 0.12 to 1 μg/mL, all isolates were resistant to ampicillin-sulbactam, nine of the 10 isolates were susceptible to tigecycline, and all 10 isolates had an intermediate phenotype to colistin. DNA sequencing revealed that all strains harbored an OXA-51-like carbapenemase, one of the major causes of carbapenem resistance in A. baumannii in Japan. In conclusion, this study showed that susceptibility to cefiderocol of MDRAB clinical isolates in Japan was equivalent to that of colistin or tigecycline. Cefiderocol could be a possible choice for the treatment of MDRAB infections.