Pathogen and Testing Profiles in Post-Infectious Irritable Bowel Syndrome Across the COVID-19 Public Health Emergency: A Retrospective Case Series.

Background/Objectives: The COVID-19 public health emergency altered enteric infection surveillance, diagnostic testing, and antibiotic prescribing. We compared pathogen/testing composition among post-infectious irritable bowel syndrome (PI-IBS) cases stratified by whether index gastroenteritis occurred before, during, or after the emergency. Methods: This single-centre retrospective case series included 138 adults with clinician-diagnosed PI-IBS classified as Rome IV-compatible by chart adjudication. Index gastroenteritis occurred from January 2019 to December 2024; existing clinical records were reviewed retrospectively. The primary comparison was a five-category pathogen/testing profile. Results: The profile differed across pre-pandemic (n = 30), pandemic (n = 39), and post-emergency (n = 69) periods (χ2 = 35.56, p < 0.001; Cramér V = 0.36, 95% CI 0.30-0.48). Bacterial/protozoal cases represented 63.3%, 7.7%, and 33.3%, respectively; SARS-CoV-2-associated cases represented 0%, 35.9%, and 13.0%. Antibiotic exposure was 56.7%, 12.8%, and 33.3%. In an exploratory adjusted model, confirmed enteric pathogens were associated with antibiotic exposure (OR 16.28, 95% CI 3.03-87.35), whereas period was not. Sensitivity analyses excluding SARS-CoV-2 cases and period-crossing diagnoses were concordant. Conclusions: Pathogen/testing and antibiotic-exposure profiles differed across periods among diagnosed PI-IBS cases. These data describe case composition, not incidence or causal risk, and cannot separate infection ecology from diagnostic behaviour.