Antibiotic Resistance in Uncomplicated UTIs


Synopsis: The days may be numbered when trimethoprim/ sulfamethoxazole should be used for empiric therapy for uncomplicated UTI.

Source: Gupta K, et al. JAMA 1999;281:736-738.

Prevalence and trends in antimicrobial resistance among the narrow spectrum of organisms responsible for acute uncomplicated cystitis were examined in this study from Washington state. Included were those patients with a positive urine culture (> 103 CFUs/mL) from a population of women, ages 18-50, in a health maintenance organization, who sought treatment at an outpatient clinic or ED. The study spanned five years, controlled for seasonal variation, and included 4342 urine isolates. Selected chart review confirmed that more than 95% of the study population included visits for uncomplicated cystitis.

The distribution of causative uropathogens was not surprising: Escherichia coli, 86%; Staphylococcus saprophyticus, 4%; Proteus species, 3%; Klebsiella species, 3%; Enterobacter species, 1.4%; Citrobacter species, 0.8%; Enterococcus species, 0.5%; and others, 1.3%. More than 20% of E. coli isolates were resistant to ampicillin, cephalothin, and sulfamethoxazole.

Alarmingly, resistance among E. coli to trimethoprim/sulfamethoxazole doubled over the course of the study, rising from 9% to 18%. A significant increasing linear trend in resistance was found for all isolates to ampicillin, cephalothin, trimethoprim, and trimethoprim/sulfamethoxazole. Ciprofloxacin, nitrofurantoin, and gentamicin fared the best with regard to limited resistance.

Recognizing that in vitro resistance may not directly translate to altered patient outcome, Gupta and colleagues conclude that the days may be numbered when trimethoprim/sulfamethoxazole should be used for empiric therapy for uncomplicated UTI.

Comment by Richard A. Harrigan, MD

And so, more evidence of emerging antimicrobial resistance is published; important news, but is it time to stop using trimethoprim/sulfamethoxazole as the first-line antibiotic for uncomplicated UTI? Not yet. As Gupta et al caution, this is not a clinical outcomes study, but rather a report of a microbiological trend. Moreover, trimethoprim/sulfamethoxazole is concentrated in the urine, achieving higher concentrations than in the blood;1 thus, the pathogen might still be eradicated. Finally, a treatment failure in cases of uncomplicated UTI generally does not result in life-threatening illness, but, rather, persistence of symptoms. Thus, treatment failures should make us think not only of an alternative diagnosis, but also of the antimicrobial resistance issue. (Dr. Harrigan is Associate Professor of Medicine, Temple University School of Medicine, Associate Research Director, Division of Emergency Medicine, Temple University Hospital, Philadelphia, Pa.)


    1. Physicians’ Desk Reference, 53rd ed. Montvale NJ: Medical Economics Company; 1999:2655.