Fosfomycin Susceptibility in Urinary Tract Enterobacteriaceae.

Introduction Antibiotic treatment of Urinary Tract Infections (UTI) is becoming increasingly difficult due to emergence of multi-drug resistant (ESBLs, AmpC, CRE) uropathogens. Fosfomycin is an old antibiotic that has evoked renewed interest with unique properties of not sharing any structural similarity and lack of cross-resistance with other antimicrobial agents. Our aim is to evaluate in-vitro activity of Fosfomycin against urinary tract Enterobacteriaceae. Material & Methods The study period was March 2014 to September 2015. All 72 isolates were identified using conventional biochemical tests. Antimicrobial susceptibility testing was performed using the automated broth microdilution system Vitek 2 (bio- Mérieux, Inc., Durham, NC). Fosfomycin susceptibility was determined by the E-test (bioMérieux, Inc., Durham, NC) method. Interpretive criteria from the Clinical and Laboratory Standards Institute (CLSI) for fosfomycin susceptibility are not available for the Enterobacteriaceae other than Escherichia coli. Therefore, results were interpreted according to criteria for E. coli (i.e., susceptible at a MIC of ≤ 64 μg/ml), as has been reported previously. Results Overall, 79.16% (57/72) isolates were susceptible to fosfomycin w i t h 92.00% (23/25) susceptibility in ESBL producing enterobacteriaceae and 72.34% (34/47) in CRE. One CRE isolate has developed resistant while on treatment. There was not much difference in number of susceptible isolates CLSI:EUCAST = 57:53,but number of resistant isolates was more with EUCAST (CLSI:EUCAST = 10:19). Conclusion Study demonstrate that, a considerable proportion (79.16%) of the multidrug-resistant Enterobacteriaceae with diverse resistance mechanisms, including ESBL and CRE, found susceptible to fosfomycin. Consequently, fosfomycin may currently be considered a useful antibiotic agent in the treatment armamentarium of UTIs.