Results of small intestinal bacterial overgrowth testing in irritable bowel syndrome patients: clinical profiles and effects of antibiotic trial.

PURPOSE Small intestinal bacterial overgrowth (SIBO) may coexist with irritable bowel syndrome (IBS) and eradication therapy has been reported as effective in reducing IBS symptoms. Aims of this study were to: (1) Assess the clinical profiles of IBS patients, who underwent breath testing with a glucose substrate--glucose breath test (GBT); (2) Evaluate hydrogen and methane parameters in various IBS groups; (3) Assess the role of inhibition of gastric acid in contributing to SIBO; (4) Investigate efficacy and safety of non-absorbable antibiotic rifamixin for eradication and symptom relief. METHODS 204 IBS patients met the ROME II criteria for IBS (170F & 34M; mean age 46.4; range 18-88) and underwent GBT. 8 of these patients with positive GBT were treated with rifaximin 200 mg, 4 times a day for 1 month and symptom assessments and GBT were repeated. RESULTS 93 (46%) had a positive GBT. 68 (73%) of these 93 IBS-diarrhea dominant (IBS-D), 12 (13%) were constipation dominant (IBS-C) and 13 (14%) IBS with alternating bowel pattern. 48% of SIBO positive patients were receiving PPI therapy compared to 40% of IBS patients with negative GBT. 61 (66%) produced only hydrogen, 27 (29%) methane only, and 5 (5%) both-hydrogen and methane. There were more methane producers in IBS-C then IBS-D group (58% vs 28%) while IBS-D had more hydrogen formers (71% vs 42%). 8 patients with SIBO (7F & IM; mean age 55, range 31-85) received rifamixin 800 mg/day. Repeat GBT was normal in 6 (75%), 1 patient (12.5%) normalized according to hydrogen criteria but methane remained positive. Symptoms score improved in 7 (87.5%) patients and no adverse events were noted. CONCLUSIONS (1) SIBO was present in nearly half of this large cohort of IBS patients based on the results of GBT; (2) Chronic PPI use was not associated with SIBO; (3) Methane formers on the GBT are more likely to be constipated; (4) Rifaximin is effective in treatment of SIBO in IBS and controlled trials are warranted.