In Vitro Activity of Fosfomycin Trometamol Against Extended-Spectrum Beta-Lactamase Producing Escherichia coli Strains Isolated from Community-Acquired Urinary Tract Infections

Introduction: Escherichia coli is the most common microorganism in community acquired UTIs. Treating infections caused by extended-spectrum beta-lactamase (ESBL) producing E. coli strains is problematic. In recent years, in our country and the world, susceptibility of E. coli strains to commonly used antibiotics in the treatment of UTIs has decreased. The aim of this study was to investigate the in vitro activity of fosfomycin in ESBL positive E. coli strainst isolated from community-acquired UTIs. Materials and Methods: The study included E. coli positive urine samples taken from outpatients in the Department of Infectious Disease and Clinical Microbiology at Ankara Training and Research Hospital between June 2012 and January 2013. Antibiotic susceptibilities of the isolates were determined by Kirby-Bauer disc diffusion method and ESBL production was confirmed by double-disc diffusion method according to the recommendations of CLSI (Clinical and Laboratory Standards Institute). Minimum inhibitor concentration (MIC) values for fosfomycin were detected by E-test method. Results: Thirty-five of the 80 E. coli strains (43.7%) producing ESBL was included into the study. However, ESBL-non producing isolates weren’t resistant to fosfomycin but ESBL-producing isolates were 8.6% resistant to fosfomycin (determined by Kirby-Bauer disc diffusion method according to CLSI recommendations). Regarding fosfomycin MIC breakpoints defined by CLSI, 100% of ESBL-producing and non-producing isolates were found susceptible to fosfomycin, indicating no significant difference between the two groups (p= 0.457). Conclusion: It isconcluded that fosfomycin isan appropriate alternative antibiotic in the treatment of community-acquired UTIs because of its high susceptibility rates