Resistance of uropathogens to fosfomycin: an evaluation of the published evidence

Fosfomycin has reemerged as a therapeutic option for both uncomplicated and complicated urinary tract infections (UTIs), demonstrating in vitro activity even against isolates with advanced antimicrobial resistance profiles. This review aimed to evaluate its in vitro activity against common urinary pathogens.

Overall, 41 studies comprising 25,689 urinary isolates of Escherichia coli, Klebsiella pneumoniae, and Enterococcus faecalis were included. Among E. coli isolates, resistance was 1.2%-54.1% and 0%-63.2% according to EUCAST and CLSI breakpoints, respectively (with 0.5%-1.5% intermediate according to CLSI). Among K. pneumoniae isolates, resistance was 13.1%-88.2% and 0%-73.6% according to EUCAST and CLSI breakpoints, respectively (with 1.6%-3.2% intermediate according to CLSI). Lastly, among E. faecalis isolates, resistance was 2.6%-66.5% and 2.1%-11.6% according to EUCAST and CLSI breakpoints, respectively.

Although routine susceptibility testing is methodologically challenging, the available data suggest that fosfomycin demonstrates in vitro activity against a considerable proportion of uropathogens. However, the use of fosfomycin in clinical practice should be guided by in vitro susceptibility testing results, given that the proportion of uropathogens resistant to the antibiotic may vary, especially in hospitalized patients. Emerging data suggest a role of fosfomycin against multidrug-resistant (MDR) and extensively drug-resistant (XDR) Gram-negative uropathogens, especially in combination therapy.