Oral antibiotic exposure and urinary tract infection risk in adults: a self-controlled case series study.

BACKGROUND

Antibiotic treatment, central to bacterial infection management, may increase urinary tract infection (UTI) risk by disrupting the microbiome. This study assessed whether oral antibiotic treatment, regardless of indication, is associated with increased UTI incidence in adults.

METHODS

A self-controlled case series study using routine-care data (2015-2024) from the Extramural LUMC Academic Network, comprising >140 general practices in the Netherlands. Adults (≥18 years) with ≥1 recorded UTI were included; individuals with <1 year of registration were excluded. Exposure was defined as an oral antibiotic treatment. UTIs were identified using International Classification of Primary Care version 1 (ICPC-1) codes for cystitis (U70) and acute pyelonephritis (U71), or UTI symptoms recorded ≤5 days of antibiotic treatment. Distinct antibiotic treatments were ≥14 days apart or had different Anatomical Therapeutic Chemical (ATC) codes. Conditional Poisson regression analyses, stratified by sex, age, and antibiotic group, estimated incidence rate ratios (IRRs) by comparing UTI incidence during risk periods (15-30, 15-90, 15-180, and 15-365 days after antibiotics) with the control period (365-15 days before antibiotics).

FINDINGS: Among 82,337 adults, 206,428 UTIs were recorded, mainly in women (79.9%) and older adults (54.8% in women >50 and 58.4% in men >65 years). The IRR was highest within 30 days (IRR: 1.74; 95% CI: 1.73-1.76): 1.98 in women ≤50 years (95% CI: 1.93-2.02), 1.52 in women >50 years (95% CI: 1.50-1.54), 3.47 in men ≤65 years (95% CI: 3.31-3.63), 2.42 in men >65 years (95% CI: 2.36-2.50), and 1.96 for β-lactams (95% CI: 1.91-2.01).

INTERPRETATION: Oral antibiotic treatment was associated with a modest increase in UTI incidence in both sexes, with the highest risk observed within 30 days. These findings may be considered when prescribing antibiotics in primary care, particularly in otherwise healthy individuals.

FUNDING: LUMC funded the study without study role.