Uncomplicated UTI: Choosing antibiotics based on resistance rates helps prevent treatment failure

In the treatment of individuals with uncomplicated urinary tract infection (UTI), the use of antibiotics with lower reported resistance rates such as amoxicillin-clavulanate and nitrofurantoin (AC + N) lowers the rate of treatment failure, as shown in a study from Singapore.

In a retrospective cohort of 3,194 women with uncomplicated UTI who received treatment at different primary care clinics in Singapore, 146 (4.57 percent) experienced treatment failure, defined as a return visit for symptoms and antibiotic represcription or hospitalization for UTI complications. [Antimicrob Resist Infect Control 2023;doi:10.1186/s13756-023-01282-4]

The incidence of treatment failure was lower among women treated with AC + N than among those who received ciprofloxacin and co-trimoxazole (C + C). Propensity-score matched analysis showed that the use of C + C was associated with about 50-percent higher likelihood of treatment failure compared with AC + N (relative risk, 1.49, 95 percent confidence interval [CI], 1.10–2.01; p=0.009).

Specifically, women treated with C + C were more likely to experience shorter time to failure (hazard ratio, 1.61, 95 percent CI 1.12–2.33; p=0.010), with the mean days to treatment failure being 26.8 days with C + C and 27.3 days with AC + N.

Of the 3,194 UTI cases included in the analysis, only 26 percent were diagnosed clinically. Urine cultures were conducted for 1,094 (34.3 percent) cases, of which only 410 (37.5 percent) had bacterial growth. Escherichia coli (64.6 percent) was the most common organism found to cause uncomplicated UTIs, with 92.6 percent and 99.4 percent of isolates sensitive to amoxicillin-clavulanate and nitrofurantoin relative to 80.0 percent and 82.5 percent for ciprofloxacin and co-trimoxazole, respectively.

“UTIs are among the top 10 principal causes of death in Singapore, and the second most common indication for antibiotic therapy in primary care in 2021,” according to the investigators. [https://www.moh.gov.sg/resources-statistics/singapore-health-facts/principal-causes-of-death; Antibiotics 2023;12:762]

A local study showed that urinary Enterobacteriaceae isolates (n=283) had high susceptibility to amoxicillin-clavulanate (86 percent) and nitrofurantoin (87 percent), with >20 percent of isolates being resistant to ciprofloxacin and co-trimoxazole. [J Clin Microbiol 2019;57:e00143-e219]

“Given the current local antibiograms, we recommend using amoxicillin-clavulanate or nitrofurantoin in the management of uncomplicated UTIs in Singapore,” they said.

This retrospective cohort study is said to be the first in Singapore to be conducted specifically on uncomplicated UTIs in primary care.

“It not only showcased UTI management practices and antibiotic prescribing patterns, but also the importance of point-of-care urinary tests in UTI diagnosis, as well as updated local antibiograms for patients with uncomplicated UTIs. This would be essential in assisting the nation in guideline development,” according to the investigators.

Future studies, they said, are necessary to update antibiograms and highlight its importance in guideline development.