Susceptibility of Nitrofurantoin and Fosfomycin Against Outpatient Urinary Isolates of Multidrug-Resistant Enterococci over a Period of 10 Years from India.

With the increasing emergence of drug resistance in enterococci, there have been very limited data on the efficacy of orally available nitrofurantoin and fosfomycin on enterococci causing urinary tract infections (UTIs), particularly for multidrug-resistant (MDR) strains. This study aimed to determine the in vitro effectiveness of these two drugs against the MDR enterococci. A total of 514 phenotypically and genotypically confirmed isolates of enterococci (239, 46.5% Enterococcus faecalis and 275, 53.5% Enterococcus faecium) showed E. faecalis as significantly more resistant (p < 0.05) to ciprofloxacin and high strength gentamicin. Vancomycin resistance was seen in 37 (7.2%) isolates. Of these, 114 (22.18%) isolates (51, 44.73% E. faecalis and 63, 55.26% E. faecium) were MDR. Nitrofurantoin minimum inhibitory concentrations (MICs) for the MDR enterococci varied from 1 to 128 μg/mL (MIC50 8 μg/mL, MIC90 64 μg/mL for E. faecalis), while fosfomycin MICs for the MDR E. faecalis, including vancomycin resistant enterococci (VRE) were in susceptible range (≤64 μg/mL, MIC50 8 μg/mL, MIC90 16 μg/mL). An efficacy ratio of ≥8 for nitrofurantoin was observed in the 39 (76.5%) MDR E. faecalis and 44 (69.8%) MDR E. faecium isolates as against the 50 (98%) E. faecalis isolates for fosfomycin. Although nitrofurantoin has been widely prescribed for the treatment of UTIs for the past several years, it was still found to be active in vitro against the urinary isolates of MDR enterococci, including VRE. As for fosfomycin, it holds robust potential to be used against the urinary MDR enterococci and VRE (E. faecalis).