Resistance trends in urinary tract pathogens and impact on management

Purpose: The prevalence of antimicrobial resistance among urinary tract pathogens is reviewed and its clinical impact on management is determined. Materials and Methods: A Medline search supplemented with references quoted in bibliographies of articles on urinary tract infections, epidemiology of antimicrobial resistance among uropathogens and clinical outcomes in urinary tract infections was conducted. Results: Although some geographic variation is noted in resistance rates among urinary tract Escherichia coli isolates, rates were highest for ampicillin (39% to 45%) and trimethoprimsulfamethoxazole (14% to 31.4%) and lowest for nitrofurantoin (1.8% to 16%) and fluoroquinolones (0.7% to 10%). Resistance rates also varied based on patient age. A few studies suggested that antimicrobial resistance impacts clinical and bacteriological outcome but the results are limited by the small number of patients. A randomized trial in women with acute uncomplicated pyelonephritis indicated that those treated with trimethoprim-sulfamethoxazole had a clinical and bacteriological success rate that was significantly lower in those patients treated with this drug when the infecting organism was resistant compared to those in whom the organism was susceptible to trimethoprim-sulfamethoxazole. Conclusions: Resistance rates among common uropathogens continue to evolve and appear to be increasing to many commonly used agents. Continued surveillance of resistance rates among uropathogens is needed to ensure that appropriate recommendations can be made for treatment of infected patients. Further studies addressing the clinical and bacteriological outcomes of patients infected with a resistant pathogen are needed.