Evaluation of in Vitro Activity of Fosfomycin and Other Antimicrobial Agents against Urinary Escherichia coli Isolates

Abstract

Objective: Fosfomycin is an antimicrobial agent commonly used in uncomplicated urinary tract infections. The objective of this study is to evaluate in vitro activity of fosfomycin against Escherichia coli strains isolated from urine specimens. Methods: Data were retrieved from two hospitals in Tekirdag, Turkey. We retrospectively examined the susceptibility results of E. coli strains collected over one year (January 2010-March 2011) to fosfomycin. Susceptibility of the isolates was determined by the disk diffusion method according to Clinical and Laboratory Standards Institute (CLSI) criteria. Results: A total of 561 E. coli strains were examined and 34 (6.1%) of the isolates were resistant to fosfomycin. Resistance was highest amongst isolates taken from outpatients (73.52%) and from the urology clinics (47.05%). In vitro activities of 561 isolates against other antimicrobial agents were also evaluated. Resistance rates of the strains against ampicillin-sulbactam, ciprofloxacin, levofloxacin, gentamicin, and amikacin were 44.8%, 19.4%, 18.1%, 15.1%, and 11.8%, respectively. Conclusions: According to data obtained from this study, fosfomycin seems to have good levels of in vitro activity against urinary E. coli isolates in our region. Further evaluation of its potential clinical effectiveness is needed in followup to these in vitro antimicrobial susceptibility results.