Increasing Prevalence of Antimicrobial Resistance Among Uropathogens Causing Acute Uncomplicated Cystitis in Women

Abstract

Context  Guidelines for the management of acute uncomplicated cystitis in women that recommend empirical therapy in properly selected patients rely on the predictability of the agents causing cystitis and knowledge of their antimicrobial susceptibility patterns.

Objective  To assess the prevalence of and trends in antimicrobial resistance among uropathogens causing well-defined episodes of acute uncomplicated cystitis in a large population of women.

Design  Cross-sectional survey of antimicrobial susceptibilities of urine isolates collected during a 5-year period (January, May, and September 1992-1996).

Setting  Health maintenance organization.

Patients  Women aged 18 to 50 years with an outpatient diagnosis of acute cystitis.

Main Outcome Measures  Proportion of uropathogens demonstrating in vitro resistance to selected antimicrobials; trends in resistance over the 5-year study period.

Results  Escherichia coli and Staphylococcus saprophyticus were the most common uropathogens, accounting for 90% of the 4342 urine isolates studied. The prevalence of resistance among E coli and all isolates combined was more than 20% for ampicillin, cephalothin, and sulfamethoxazole in each year studied. The prevalence of resistance to trimethoprim and trimethoprim-sulfamethoxazole rose from more than 9% in 1992 to more than 18% in 1996 among E coli, and from 8% to 16% among all isolates combined. There was a statistically significant increasing linear trend in the prevalence of resistance from 1992 to 1996 amongE coli and all isolates combined to ampicillin (P<.002), and to cephalothin, trimethoprim, and trimethoprim-sulfamethoxazole (P<.001). In contrast, the prevalence of resistance to nitrofurantoin, gentamicin, and ciprofloxacin hydrochloride was 0% to 2% among E coli and less than 10% among all isolates combined, and did not change significantly during the 5-year period.

Conclusions  While the prevalence of resistance to trimethoprim-sulfamethoxazole, ampicillin, and cephalothin increased significantly among uropathogens causing acute cystitis, resistance to nitrofurantoin and ciprofloxacin remained infrequent. These in vitro susceptibility patterns should be considered along with other factors, such as efficacy, cost, and cost-effectiveness in selecting empirical therapy for acute uncomplicated cystitis in women.