Fosfomycin Susceptibility among Urinary Enterococcus Faecalis with High Level Aminoglycoside and Glycopeptide Resistant Phenotypes

Fosfomycin, a broad spectrumbactericidal agent had been recommended by the Food and Drug Administration for the treatment of uncomplicated urinary tract infections. However, studies on the susceptibility rate of Enterococcus faecalis against fosfomycin are inadequate. Hence, this study was aimed to determine the invitro susceptibility to fosfomycinamong urinary E. faecalis. A total of about 70 non-repetitive isolates of Enterococcus faecalis isolated from the urine samples were included in the study. Susceptibility to fosfomycin, linezolid, teicoplanin, high level gentamicin, high level streptomycin was determined by Kirby Bauer disk diffusion method. Preliminary screening to minimum inhibitory concentration of high level aminoglycosides was assessed by agar dilution method. Vancomycin resistance was detected by agar screening method and further confirmed with e-test and interpreted as per CLSI guidelines. Our results indicate, increased susceptibility to teicoplanin (98.57%) followed by fosfomycin (95.71%) and linezolid (68.57%). Of note, none of the isolates were resistant to vancomycin. Of the 70 E. faecalis isolates screened, 61.43% isolates exhibited HLG^R phenotype) and 37.14% exhibited HLS^R phenotype. HLG^RHLS^R phenotype was observed among 32.9% of the isolates. MIC of gentamicin and streptomycin was found to be ≥512μg/ mL (HLGR isolates) and ≥2000μg/mL (HLSR isolates) respectively. 91.3% of our HLAR isolates (93% HLGR, 92.3% HLSR) were susceptible to fosfomycin. Hence, it could be speculated that fosfomycin can be considered in the treatment of uncomplicated urinary tract infections caused by high level aminoglycoside/ linezolid resistant/glycopeptide resistant E.faecalis.