Antimicrobial resistance in uncomplicated urinary tract infections in 3 California EDs

Abstract

Background: Increased trimethoprim/sulfamethoxazole (TMP/SMX) resistance has led to changes in empiric treatment of female urinary tract infections (UTI) in the emergency department (ED), particularly increased use of fluoroquinolones (Acad Emerg Med.2009;16(6):500-507). Whether prescribing changes have affected susceptibility in uropathogens is unclear. Using narrow-spectrum agents and therapy tailored to local susceptibilities remain important goals.

Objective: The primary goal of this study is to characterize the susceptibility patterns of uropathogens among ambulatory female ED patients with UTI. Its secondary goal is to identify demographic or clinical factors predictive of resistance to narrow-spectrum agents.

Methods: This was a cross-sectional study of women with suspected UTI referred to a trial of computer kiosk-aided treatment of UTI in 3 Northern California EDs. Demographic and clinical data were gathered from the kiosk and chart, and features associated with resistance were identified by bivariate and multivariable regression analysis.

Results: Two hundred eighty-three participants, aged 15 to 84 years, were diagnosed with UTI and cultured. One hundred thirty-five (48%) of cultures were positive, with full susceptibilities reported (81% Escherichia coli). Only 2 isolates (1.5%) were fluoroquinolone resistant. Resistance to TMP/SMX was 18%, to nitrofurantoin 5%, and to cefazolin 4%. Seventy-four percent were sensitive to all 3 narrow-spectrum agents. Resistance to narrow-spectrum agents did not vary significantly by diagnosis, age, recent UTI, or any clinical or demographic factors; but overall, there was a trend toward lower resistance rates in our population than in our hospitals' published antibiograms.

Conclusion: In our population of ambulatory female ED patients, resistance to TMP/SMX is just below the 20% threshold that the Infectious Disease Society of America recommends for continued empiric use (Clin Infect Dis.1999;29(4):745-758, Clin Infect Dis.2011;52(5):e103-120), whereas resistance to other narrow-spectrum agents, such as nitrofurantoin and cephalexin, may be lower than published antibiograms for our sites. Fluoroquinolone resistance remains very low.