Microbiological findings, antibiotic resistance rates and prescription practices for older women with recurrent urinary tract infections: a descriptive study alongside a multinational randomized controlled trial (ImpresU)

OBJECTIVES: To describe microbiological findings during asymptomatic and symptomatic phases in older women with recurrent urinary tract infections (rUTIs), to evaluate whether antimicrobial resistance patterns of Escherichia coli among methenamine hippurate users differ from untreated controls, and to explore prescription patterns of UTI antibiotics.

METHODS: This was a descriptive study alongside a multinational randomized controlled trial (ImpresU). Women aged ≥70 years with rUTIs were recruited from general practice in Norway, Sweden, Poland and the Netherlands between December 2019 and June 2022. Participants were randomized to methenamine hippurate 1 g or placebo twice daily for 6 months, followed by a 6 month follow-up period. Urinary samples were collected at baseline (asymptomatic) and during acute UTIs.

RESULTS: We included 281 women. A dominating uropathogen ≥105 cfu/mL was detected in 29% of the baseline urine samples. Of the 178 urinary cultures taken at acute UTIs, 163 (92%) had bacterial growth, of which a minority (10%) were reported as mixed flora. E. coli was most frequently detected both at baseline and in acute UTIs (present in any concentration in 32% versus 60% of urine samples), with highest resistance to amoxicillin (36% versus 43%), trimethoprim (16% versus 22%) and amoxicillin/clavulanate (12% versus 16%). ESBL-producing E. coli at baseline were rare (4.1%). Phylogenetic subgroup B2 was the most frequent E. coli phylotype at baseline (52%). No relevant differences in antimicrobial resistance rates were found between methenamine hippurate users and controls. Narrow-spectrum antibiotics were widely prescribed, and guideline adherence was high.

CONCLUSIONS: Physicians should be aware that 29% of older women with rUTIs in the community may have significant bacterial findings in their urine during asymptomatic phases.