In Vitro Activity of Fosfomycin Against Extended Spectrum-beta-Lactamase (ESBL) Producing Escherichia coli and Klebsiella pneumoniae Strains

Escherichia coli and Klebsiella pneumoniae are the most commonly isolated microorganisms in cases of uncomplicated lower urinary tract infection (UTI). Because of the increased isolation of extended-spectrum beta-lactamase (ESBL) producing E. coli and K. pneumoniae from the urine samples of uncomplicated UTI, it is important to find alternative oral drugs for the treatment of such infections. In this purpose fosfomycin may be a useful alternative for treatment because of its pharmacokinetic and microbiological properties. Therefore, this study aimed to test the in vitro susceptibility of 100 ESBL producing clinical urinary isolates, including 80 E. coli and 20 K. pneumoniae, to fosfomycin trometamol (FT) in comparison with amoxicillin/ clavulanate (AMC), ciprofloxacin (CIP), carbapenem (IPM), and trimethoprim/sulphametoxazole (SXT). In E. coli strains the highest resistance rate was observed in SXT 66.2%, followed by CIP 53.8%, and then AMC 18.8%. Similar to the percentages of resistance in K. pneumoniae strains were found to be 75% for SXT, 25% for CIP, 10% for AMC. Only ESBL producing one E. coli and one K. pneumoniae strain were found resistant to fosfomycin and imipenem. This data showed excellent activity of FT against ESBL producing E. coli and K. pneumoniae isolates and FT is being regarded as a new treatment alternative in the ESBL producing strains related lower urinary tract infection.