SIBO (Small Intestinal Bacterial Overgrowth) is a disease of unknown etiology, and its incidence is difficult to estimate due to the lack of ideal diagnostic methods. The disease is characterized by an increased amount of bacteria in the small intestine, manifesting gastrointestinal symptoms including abdominal discomfort, gas, excessive gas production, diarrhea and indigestion of varying severity and duration. Due to the lack of specific symptoms, the disease remains undiagnosed for a long time. Excessive bacterial accumulation in the small intestine may be caused by overuse of proton pump inhibitors (PPIs) or opioids. It is believed that abdominal surgery and gastrointestinal motility disorders may be a factor predisposing to the development of the disease. A correlation was also observed in the occurrence of SIBO in people with other gastrointestinal ailments such as: IBS, inflammatory bowel disease, diverticulitis, pancreatitis or hormonal disorders such as hypothyroidism and diabetes, or other Parkinson’s disease, restless legs syndrome, systemic sclerosis.
In order to make a diagnosis, a culture/aspiration test is performed from the initial section of the small intestine, which is considered the best diagnostic method in SIBO. Non-invasive breathing tests using glucose or lactulose, which measure the release of hydrogen, methane and carbon dioxide at the appropriate time after consuming sugar, are becoming increasingly common. Despite their simplicity and non-invasiveness, these tests require more detailed verification of the cut-off points and further standardization and validation of the method. Scientists are also developing new, intelligent methods to detect bacteria using a capsule system.
The first-line treatment for SIBO is the use of broad-spectrum antibiotics that eradicate bacteria from the gastrointestinal tract. Some studies confirm the effectiveness of well-tolerated rifaximin, norfloxacin and metronizadol. Despite the introduced treatment, up to 40% of patients constantly experience symptoms of the disease, which may be caused by gastrointestinal motility disorders, the use of PPIs or colonization with antibiotic-resistant strains. Relapses can occur in up to 44% within 9 months after initial treatment. In such patients, it is recommended to identify the microorganisms in the intestine and to select an appropriately targeted antibiotic therapy. In complicated cases, experts recommend cyclical treatments with low doses of antibiotics. Due to the occurrence of relapses and significant side effects of the use of antibiotics, treatment is sought in other forms of therapy. Scientists are studying the effects of probiotics or dietary modifications on the severity of SIBO symptoms, but further research is needed in order to be able to draw unanimous conclusions.
FMT in SIBO
The positive effect of FMT on the composition and diversity of the gut microbiota in the recipient initiated the perception of FMT as one of the potential treatment options. In a clinical study by Fenghua Xu et al. from 2021 in which 55 patients with SIBO participated, the lactulose hydrogen test was used, and the diversity of the gut microbiota was assessed. Compared to the placebo group, the bacterial diversity increased significantly in patients with SIBO after FMT, which could directly contribute to the reduction of gastrointestinal symptoms in this group. Gut microbiota transplantation may become a promising therapy for SIBO patients. It is necessary to carry out more carefully conducted research in this direction.
Recently, there has been an increasing awareness of SIBO among doctors and other medical professionals and the development of diagnostic methods. We are hopefully waiting for a breakthrough in the detection and treatment of SIBO in the future.
Rao SSC, Bhagatwala J. Small Intestinal Bacterial Overgrowth: Clinical Features and Therapeutic Management. Clin Transl Gastroenterol. 2019 Oct;10(10):e00078. doi: 10.14309/ctg.0000000000000078. PMID: 31584459; PMCID: PMC6884350.
Xu, F., Li, N., Wang, C. et al. Clinical efficacy of fecal microbiota transplantation for patients with small intestinal bacterial overgrowth: a randomized, placebo-controlled clinic study. BMC Gastroenterol 21, 54 (2021). https://doi.org/10.1186/s12876-021-01630-x