Association Between Antibiotic Use for Non-Gastrointestinal Infections and Inflammatory Bowel Diseases Flare-Ups: A Self-Controlled Case Series Study

Background: 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 non-gastrointestinal (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 (SCCS) study using territory-wide electronic medical records from Hong Kong. Adults with IBD who experienced at least one flare-up and received at least one course of antibiotics for infections outside the GI tract between 2000 and 2024 were included, to reduce indication bias related to gastrointestinal 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 two weeks after treatment (IRR 4.79), and returned to baseline levels within six months, versus baseline. Increased incidences were observed for oral antibiotics during and two weeks after treatment (IRRs 3.91 and 3.70), but not for injectable antibiotics (interaction p-values <0.01). The IRRs for broad-spectrum antibiotics were higher than those for narrow-spectrum agents from one month before to six weeks after antibiotic use, versus baseline. Conclusions: Antibiotic use for non-GI infections was associated with a short-term increase in IBD flare risk. Injectable or narrow-spectrum antibiotics may have a relatively smaller impact on potential IBD flare-ups.