Methanobrevibacter smithii in irritable bowel syndrome: A clinical and molecular study

Abstract

Aim. To assess the role of Methanobrevibacter smithii in patients with irritable bowel syndrome associated with small intestinal bowel overgrowth. Materials and methods. Sixty-seven patients with IBS according to Rome IV were enrolled into the study in whom hydrogen breath test was performed. Thirty-two healthy subjects with negative breath test was used as a control. All IBS symptoms assessed daily with 5 grade Lykert scale for 7 days, stool was assessed by Brystol stool scale. M. smithii was confirmed in stool samples by PCR. Results and discussion. In 67 IBS patients CH4 overproduction was found in 32 (47.7%), H2 overproduction in 31 (46.2%) and normal values in 4 (5.9%) by hydrogen breath test. M. smithii was confirmed by stool PCR in all patients with CH4 overproduction. Severity and prevalence of main clinical features of IBS were similar in both SIBO groups but were significantly higher than in control (p<0.01). Positive correlation between overproduction of CH4, abdominal pain and uncomplete bowel emptying (p<0.05). Conclusion. SIBO CH4 was found in nearly half of all patients with IBS associated with SIBO, symptoms profile and severity are similar in patients with SIBO CH4 and SIBO H2, however, the abdominal pain and uncomplete bowel emptying are associated with the level of CH4 overproduction.