UC Berkeley

Community-acquired urinary tract infections (CA-UTI) are common in young women. Reports of increasing resistance to the antimicrobial drugs commonly prescribed to treat CA-UTI, evidence of wide-spread dissemination of strains of multi-drug resistant Escherichia coli that can cause community outbreaks and expanding appreciation of the importance of the rational use of antibiotics are challenging the traditional management of this disease.

Two population-based studies were performed to investigate the epidemiological features of CA-UTI with an emphasis on the antimicrobial resistance of causative bacteria. An eight-year retrospective cohort study was conducted in a large health maintenance organization to identify changes in uropathogen etiology and antimicrobial resistance and in empirical antimicrobial treatment practices and outcomes. A cross-sectional study was performed in a university population to investigate the relationship between changes in the prevalence of genotype-based clonal groups of uropathogen E. coli and the prevalence of antimicrobial resistance.

From 1998 through 2005, less than 20% of the Escherichia coli causing uncomplicated CA-UTI (UCA-UTI) were resistant to the first line empirical treatment antimicrobial, trimethoprim/sulfamethoxazole (TMP/SMX). No trends were detected in the proportions of Escherichia coli that were resistant to TMP/SMX or to nitrofurantoin. In contrast, a small but steady increase in the proportion of Escherichia coli that were resistant to ciprofloxacin was observed. Over the same period of time, the use of ciprofloxacin as empirical treatment for UCA-UTI steadily increased while the use of TMP/SMX decreased. No sustained decreases in treatment failure or in microbiologically incompatible treatment were detected. Thus TMP/SMX remains a viable empirical treatment for women with UCA- UTI in these populations.

Molecular typing of Escherichia coli causing CA-UTI revealed that the prevalence of antimicrobial resistance was influenced by a small number of Escherichia coli clonal groups. This suggests that the prevalence of antimicrobial resistant UTI in a community is not only the result of community prescribing practices and individual antimicrobial use but can be significantly impacted by the introduction and circulation of strains of uropathogens that are already drug resistant. Thus, strategies developed to maintain the usefulness of empirical treatment options for CA-UTI must include interventions that target sources of antimicrobial resistant uropathogens.