Fosfomycin tromethamine as second agent for the treatment of acute, uncomplicated urinary tract infections in adult female patients in The Netherlands?

Background: Uncomplicated urinary tract infections (UTIs) are common among female patients. According to the national guidelines of the Dutch College of General Practitioners (GPs), the drugs of first and second choice as therapy for UTIs are nitrofurantoin and trimethoprim with resistance percentages of 2% and 23%, respectively. The third choice is fosfomycin tromethamine for which no current resistance data from The Netherlands are available. The aim of this study was to determine these resistance percentages. Methods: During 2003-04, urine samples were collected from a representative sample of 21 general practices spread over The Netherlands, the Sentinel Stations of The Netherlands Institute for Health Services Research (NIVEL). Escherichia coli isolated from female patients visiting their GP with symptoms of an acute, uncomplicated UTI were used. Fosfomycin tromethamine susceptibility was determined by Etests. An MIC of fosfomycin tromethamine of 64 mg/L or lower was considered to indicate susceptibility, and MIC values of 96 mg/L or higher were considered to indicate resistance. E. coli ATCC 25922 was used as a reference strain. Results: In total, 1705 E. coli strains were tested, of which 11 (0.65%) were resistant to fosfomycin tromethamine. The MIC50 and MIC90 values for this population were 1 and 4 mg/L, respectively. Within the inhibition zone of 162 susceptible E. coli, resistant mutant colonies were observed, of which after repetition of the susceptibility testing 68 were resistant. In total, 79 (5%) strains were resistant to fosfomycin tromethamine. There was no cross-resistance observed between fosfomycin tromethamine and other antimicrobial agents tested previously. Conclusions: The high in vitro susceptibility to fosfomycin tromethamine in this population and the lack of cross-resistance between fosfomycin tromethamine and other agents together with the extensive global clinical experience support the choice of the national guidelines of the Dutch College of GPs to include fosfomycin tromethamine as a therapeutic option in general practice for uncomplicated UTIs.