Small intestinal bacterial overgrowth is common in celiac disease but is not associated with Marsh score

Abstract Celiac disease (CeD) is associated with abnormalities of the gut microbiota including gastrointestinal microbial overgrowth (MO). We assessed the prevalence of positive MO tests among patients with CeD and correlated with CeD activity. Among patients with confirmed CeD, we selected those who had undergone testing either with intestinal aspirate culture or glucose or lactulose hydrogen/methane breath testing. For patients who underwent cultures, we obtained Marsh score from biopsies taken during the same endoscopy. From 256 patients who underwent aspirate culture, 17.6% had small intestinal bacterial overgrowth (SIBO) at a threshold of ≥10 5 CFU/mL, and 49.6% at ≥10 3 CFU/mL. Small intestinal fungal overgrowth was seen in 4.3%, 45.5% in conjunction with SIBO. There was no association between SIBO and Marsh scores ( p = 0.153 and 0.884 for the higher and lower thresholds, respectively). However, refractory CeD was more likely to have SIBO (36.8% vs. 16%, p = 0.053; 78.9% vs. 47.3%, p = 0.008, at the higher and lower thresholds, respectively). Of 39 patients who underwent breath tests (36 glucose, 3 lactulose), 9 (23.1%) had positive results, 100% due to intestinal methanogen overgrowth (with or without elevated hydrogen). MO is common in patients with CeD, especially in refractory disease.