Association Between Antibiotic Use for Nongastrointestinal Infections and Inflammatory Bowel Disease Flare-Ups: A Self-Controlled Case Series Study

INTRODUCTION: Disruption of gut microbiota by antibiotic use has been linked to the development of inflammatory bowel disease (IBD). This study aimed to evaluate the association between antibiotic use for nongastrointestinal (GI) infections and the risk of IBD flare-ups, and to examine whether route of administration, antimicrobial spectrum, and antibiotic class modulate this risk. METHODS: We conducted a self-controlled case series study using territory-wide electronic medical records from Hong Kong. Adults with IBD who experienced at least 1 flare-up and received at least 1 course of antibiotics for infections outside the GI tract between 2000 and 2024 were included, to reduce indication bias related to GI symptoms. Conditional Poisson regression models were used to estimate incidence rate ratios (IRRs) by comparing across predefined risk periods to the baseline period. RESULTS: Among 810 patients, IBD flare incidence was elevated during the month preceding antibiotics (IRR 2.85), increased further during treatment (IRR 3.44), and peaked within 2 weeks after treatment (IRR 4.79), and returned to baseline levels within 6 months, vs baseline. Increased incidences were observed for oral antibiotics during and 2 weeks after treatment (IRRs 3.91 and 3.70), but not for injectable antibiotics (interaction P values