SMALL INTESTINAL MICROBIAL OVERGROWTH (SIBO, IMO, AND SIFO) IN THE PATHOGENESIS AND MANAGEMENT OF IRRITABLE BOWEL SYNDROME

Julia Danieluk; Natalia Adamaszek; Michał Gliński; Urszula  Kacprzak; Dominika Dołęga-Mostowska; Julia Sochowska; Agnieszka  Buczkowska; Laura Stochaj; Michalina Flejszman; Justyna Wójcik

doi:10.31435/ijitss.3(51).2026.5974

Authors

Julia Danieluk Clinical Hospital of Poznań University of Medical Sciences, 49 Przybyszewskiego Street, 60-355 Poznań, Poland https://orcid.org/0009-0000-1513-6814
Natalia Adamaszek Clinical Hospital of Poznań University of Medical Sciences, 49 Przybyszewskiego Street, 60-355 Poznań, Poland https://orcid.org/0009-0007-7839-1581
Michał Gliński Clinical Hospital of Poznań University of Medical Sciences, 49 Przybyszewskiego Street, 60-355 Poznań, Poland https://orcid.org/0009-0003-1422-6940
Urszula Kacprzak Clinical Hospital of Poznań University of Medical Sciences, 49 Przybyszewskiego Street, 60-355 Poznań, Poland https://orcid.org/0009-0008-2380-3187
Dominika Dołęga-Mostowska Medical University of Lodz, al. Tadeusza Kościuszki 4, 90-419 Łódź, Poland https://orcid.org/0009-0003-5448-9956
Julia Sochowska Clinical Hospital of Poznań University of Medical Sciences, 49 Przybyszewskiego Street, 60-355 Poznań, Poland https://orcid.org/0009-0001-9484-6634
Agnieszka Buczkowska Clinical Hospital of Poznań University of Medical Sciences, 49 Przybyszewskiego Street, 60-355 Poznań, Poland https://orcid.org/0009-0009-3488-2949
Laura Stochaj Provincial Hospital in Poznań, 7/19 Juraszów Street, 60-479 Poznań, Poland https://orcid.org/0009-0004-0795-2992
Michalina Flejszman Poznań University of Medical Sciences, 10 Fredry Street, 61-701 Poznań,Poland https://orcid.org/0009-0007-9936-6975
Justyna Wójcik Clinical Hospital of Poznań University of Medical Sciences, 49 Przybyszewskiego Street, 60-355 Poznań, Poland https://orcid.org/0009-0007-2270-5027

DOI:

https://doi.org/10.31435/ijitss.3(51).2026.5974

Keywords:

IBS, SIBO, IMO, Dysbiosis, Microbiome, SIFO

Abstract

Background. Irritable Bowel Syndrome (IBS) is a complex functional disorder characterized by abdominal pain and altered bowel habits. Small Intestinal Bacterial Overgrowth (SIBO) is increasingly recognized as a key pathogenetic factor, shifting the understanding of IBS toward a micro-organic basis. IBS is viewed as a heterogeneous condition with distinct phenotypes: microbiota-driven, post-infectious (PI-IBS), centrally mediated, and genetic variants.

Aim. To evaluate the role of SIBO, Intestinal Methanogen Overgrowth (IMO), and Small Intestinal Fungal Overgrowth (SIFO) in IBS pathogenesis, focusing on prevalence, mechanisms, and targeted therapy.

Material and methods. A literature review was performed using PubMed and Scopus (2000 - 2025). The analysis included 45 sources, including meta-analyses, systematic reviews, and clinical guidelines (Rome IV, Polish Society of Gastroenterology).

Results. Meta-analyses indicate that IBS patients are nearly five times more likely to test positive for SIBO than healthy individuals (OR 4.7). Hydrogen-producing bacteria are linked to diarrhea (IBS-D), while methane delays transit, correlating with constipation (IBS-C). Proposed mechanisms include excessive fermentation gas, bile acid deconjugation, and increased intestinal permeability. SIFO is found in 25% of refractory cases. Targeted eradication particularly with rifaximin achieves symptom resolution, with 48% of treated patients no longer meeting Rome criteria. However, diagnostic inconsistencies in breath tests remain a subject of clinical controversy.

Conclusions. SIBO and IMO represent treatable pathomechanisms in a subset of IBS patients, supporting a transition to personalized, mechanism-based management. Identifying these phenotypes is essential for optimizing targeted antimicrobial and prokinetic therapy. Individualized diagnostics are crucial for managing the micro-organic subtype of this complex syndrome.

References

Banaszak, M., Górna, I., Woźniak, D., Przysławski, J., & Drzymała-Czyż, S. (2023). Association between gut dysbiosis and the occurrence of SIBO, LIBO, SIFO, and IMO. Microorganisms, 11(3), 573. https://doi.org/10.3390/microorganisms11030573

Barbara, G., Grover, M., Bercik, P., Corso, G., Cremon, C., Ohman, L., & Spiller, R. C. (2019). Rome Foundation working team report on post-infection irritable bowel syndrome. Gastroenterology, 156(1), 46–58.e7. https://doi.org/10.1053/j.gastro.2018.07.011

Bures, J., Cyrany, J., Kohoutova, D., Förstl, M., Rejchrt, S., Kvetina, J., Vorisek, V., & Kopacova, M. (2010). Small intestinal bacterial overgrowth syndrome. World Journal of Gastroenterology, 16(24), 2978–2990. https://doi.org/10.3748/wjg.v16.i24.2978

Chen, B., Kim, J., Zhang, Y., Du, L., & Dai, N. (2018). Prevalence and predictors of small intestinal bacterial overgrowth in irritable bowel syndrome: A systematic review and meta-analysis. Journal of Gastroenterology, 53, 807–818. https://doi.org/10.1007/s00535-018-1476-9

Chey, W. D., Shah, E. D., & DuPont, H. L. (2020). Mechanism of action and therapeutic benefit of rifaximin in patients with irritable bowel syndrome: A narrative review. Therapeutic Advances in Gastroenterology, 13, 1756284819897531. https://doi.org/10.1177/1756284819897531

David, L., Babin, A., Picos, A., & Dumitrascu, D. L. (2014). Small intestinal bacterial overgrowth is associated with intestinal inflammation in irritable bowel syndrome. Journal of Gastrointestinal and Liver Diseases, 23(4), 403–408. https://doi.org/10.3748/wjg.v20.i10.2482

Ford, A., Spiegel, B., Talley, N., & Moayyedi, P. (2009). Small intestinal bacterial overgrowth in irritable bowel syndrome: Systematic review and meta-analysis. Clinical Gastroenterology and Hepatology, 7(12), 1279–1286. https://doi.org/10.1016/j.cgh.2009.06.031

Gajewski, P. (Ed.). (2024). Interna Szczeklika 2024. Medycyna Praktyczna.

Gandhi, A., Shah, A., Jones, M. P., Koloski, N., Talley, N. J., Morrison, M., & Holtmann, G. (2021). Methane-positive small intestinal bacterial overgrowth in inflammatory bowel disease and irritable bowel syndrome: A systematic review and meta-analysis. Gut Microbes, 13(1), 1933313. https://doi.org/10.1080/19490976.2021.1933313

Ghoshal, U., Nehra, A., Mathur, A., & Rai, S. (2019). A meta-analysis on small intestinal bacterial overgrowth in patients with different subtypes of irritable bowel syndrome. Journal of Gastroenterology and Hepatology, 35, 922–931. https://doi.org/10.1111/jgh.14938

Ghoshal, U. C., Kumar, S., Mehrotra, M., Lakshmi, C. P., & Misra, A. (2010). Frequency of small intestinal bacterial overgrowth in patients with irritable bowel syndrome and chronic non-specific diarrhea. Journal of Neurogastroenterology and Motility, 16(1), 40–46. https://doi.org/10.5056/jnm.2010.16.1.40

Ghoshal, U. C., Shukla, R., & Ghoshal, U. (2017). Small intestinal bacterial overgrowth and irritable bowel syndrome: A bridge between functional organic dichotomy. Gut and Liver, 11(2), 196–208. https://doi.org/10.5009/gnl16126

Ghoshal, U. C., & Srivastava, D. (2014). Irritable bowel syndrome and small intestinal bacterial overgrowth: Meaningful association or unnecessary hype. World Journal of Gastroenterology, 20(10), 2482–2491. https://doi.org/10.3748/wjg.v20.i10.2482

Giorgio, V., Scarpellini, E., Roccarina, D., Cammarota, G., Pantanella, A., & Fundarò, C. (2013). Prevalence of small bowel bacterial overgrowth in children with irritable bowel syndrome: A case-control study. Journal of Pediatric Gastroenterology and Nutrition, 57(5), 611–615. https://doi.org/10.1016/j.jpeds.2009.03.033

Hillestad, E. M. R., van der Meeren, A., Nagaraja, B. H., Bjørsvik, B. R., Haleem, N., Benitez-Paez, A., Sanz, Y., Hausken, T., Lied, G. A., Lundervold, A., & Berentsen, B. (2022). Gut bless you: The microbiota-gut-brain axis in irritable bowel syndrome. World Journal of Gastroenterology, 28(4), 412–431. https://doi.org/10.3748/wjg.v28.i4.412

Jaworowska, A., Dudzińska, E., Zagórska, J., & Koch, W. (2025). Pathogenesis and treatment of irritable bowel syndrome. Medical Studies/Studia Medyczne, 41(3), 179–188. https://doi.org/10.5114/ms.2025.154432

Karoń, Ł., Zygmunt, A., Karoń, K., Pedrycz, D., Drapała, G., Grabowski, W., & Pedrycz, E. (2024). Targeting the microbiome: The role of low-FODMAP diet in modulating gut health for IBS and inflammatory conditions. Journal of Education, Health and Sport, 75, 56153. https://doi.org/10.12775/JEHS.2024.75.56153

Łabuda, M., Bogucka, A., Mentel, O., Sowińska, T., Szema, A., Sikora, J., & Knychalska, K. (2025). Mechanism of action, efficacy, and adverse events of selected drugs used to treat irritable bowel syndrome (IBS): A literature review. Journal of Education, Health and Sport, 81, 59982. https://doi.org/10.12775/JEHS.2025.81.59982

Lacy, B. E., & Patel, N. K. (2017). Rome criteria and a diagnostic approach to irritable bowel syndrome. Journal of Clinical Medicine, 6(11), 99. https://doi.org/10.3390/jcm6110099

Litwiniuk, M., Zaniuk, M., Hurkała, K., Antonik, D., Denys, B., Góra, K., & Iberszer, K. (2023). Treatment of small intestinal bacterial overgrowth: Conventional antibiotic therapy and alternative therapy—Probiotics and low FODMAP diet. Journal of Education, Health and Sport, 41(1), 57–69. https://doi.org/10.12775/JEHS.2023.41.01.005

Lu, S., Chen, Y., Guo, H., Liu, Z., Du, Y., & Duan, L. (2020). Differences in clinical manifestations and the fecal microbiome between irritable bowel syndrome and small intestinal bacterial overgrowth. BMC Gastroenterology, 20, 132. https://doi.org/10.1016/j.dld.2024.07.011

Mayo Clinic. (2023). Small intestinal bacterial overgrowth (SIBO): Symptoms and causes. https://www.mayoclinic.org/diseases-conditions/small-intestinal-bacterial-overgrowth/symptoms-causes/syc-20370168

Mearin, F., Lacy, B. E., Chang, L., Chey, W. D., Lembo, A. J., Simren, M., & Spiller, R. (2016). Bowel disorders. Gastroenterology. Advance online publication. https://doi.org/10.1053/j.gastro.2016.02.031

Park, H. (2010). The role of small intestinal bacterial overgrowth in the pathophysiology of irritable bowel syndrome. Journal of Neurogastroenterology and Motility, 16, 3–4. https://doi.org/10.5056/jnm.2010.16.1.3

Pawełek, K., Marta, P. K., Huzarski, F. M., Ferfecka, G. M., Rosa-Bończak, M., Ossolińska, A., & Morawiecka, N. (2025). What do gases in the large intestine have to do with health? Journal of Education, Health and Sport, 78, 57693. https://doi.org/10.12775/JEHS.2025.78.57693

Pimentel, M., Chow, E. J., & Lin, H. C. (2000). Eradication of small intestinal bacterial overgrowth reduces symptoms of irritable bowel syndrome. American Journal of Gastroenterology, 95(12), 3503–3506. https://doi.org/10.1111/j.1572-0241.2000.03368.x

Poon, D., Law, G., Major, G., & Andreyev, H. (2022). A systematic review and meta-analysis on the prevalence of non-malignant, organic gastrointestinal disorders misdiagnosed as irritable bowel syndrome. Scientific Reports, 12. https://doi.org/10.1038/s41598-022-05933-1

Saha, L. (2014). Irritable bowel syndrome: Pathogenesis, diagnosis, treatment, and evidence-based medicine. World Journal of Gastroenterology, 20(22), 6759–6773. https://doi.org/10.3748/wjg.v20.i22.6759

Sánchez-Pellicer, P., Álamo-Marzo, J. M., Martínez-Villaescusa, M., Núñez-Delegido, E., Such-Ronda, J. F., Huertas-López, F., Serrano-López, E. M., Martínez-Moreno, D., & Navarro-López, V. (2021). Comparative analysis of gut microbiota in patients with irritable bowel syndrome and healthy controls. Biomedicines, 9(10), 1431. https://doi.org/10.3390/jcm14041198

Schmulson, M. J., Cruz-Rico, C. L., Mendoza-Domínguez, G., Zaragoza-Galicia, S. A., & Morales-Guzmán, A. S. (2025). Diagnosis of irritable bowel syndrome. Clínicas de Gastroenterología de México, 25(1), 1–9. https://doi.org/10.24875/CGME.M25000006

Shah, A., Talley, N. J., Jones, M., Kendall, B. J., Koloski, N., Walker, M. M., Morrison, M., & Holtmann, G. J. (2020). Small intestinal bacterial overgrowth in irritable bowel syndrome: A systematic review and meta-analysis of case-control studies. The American Journal of Gastroenterology, 115(2), 165–178. https://doi.org/10.14309/ajg.0000000000000504

Sieradzka, I., Wajda, K., Mika, W., & Słowik, J. (2026). Dietary and lifestyle factors associated with small intestinal bacterial overgrowth (SIBO): A review from a health education perspective. Journal of Education, Health and Sport, 87, 67772. https://doi.org/10.12775/JEHS.2026.87.67772

Silva, B. C. da, Ramos, G. P., Barros, L. L., Ramos, A. F. P., Domingues, G., Chinzon, D., & Passos, M. do C. F. (2025). Diagnosis and treatment of small intestinal bacterial overgrowth: An official position paper from the Brazilian Federation of Gastroenterology. Arquivos de Gastroenterologia, 62, e24107. https://doi.org/10.1590/S0004-2803.24612024-107

Siragusa, N., Baldassari, G., Ferrario, L., Passera, L., Rota, B., Pavan, F., Santagata, F., Capasso, M., Londoni, C., Manfredi, G., Consalvo, D., Lasagni, G., Pozzi, L., Lombardo, V., Mascaretti, F., Scricciolo, A., Roncoroni, L., Elli, L., Vecchi, M., & Costantino, A. (2021). The ten dietary commandments for patients with irritable bowel syndrome: A narrative review with pragmatic indications. Nutrients, 13(10), 3443. https://doi.org/10.3390/nu17152496

Spiegel, B. M. R. (2011). Questioning the bacterial overgrowth hypothesis of irritable bowel syndrome: An epidemiologic and evolutionary perspective. Gastroenterology, 140(6), 1868–1871. https://doi.org/10.1016/j.cgh.2011.02.030

Strużek, K., Karamus, K., Rejmak, R., Biłogras, J., Borowska-Łygan, M., Urban, W., & Tomaszewski, J. (2025). Low-FODMAP diet in the treatment of irritable bowel syndrome—Efficacy, comparison with other diets, mechanisms, and clinical applications. Journal of Education, Health and Sport, 80, 59059. https://doi.org/10.12775/JEHS.2025.80.59059

Su, T., Liu, R., Lee, A., Long, Y., Du, L., Lai, S., Chen, X., Wang, L., Si, J., Owyang, C., & Chen, S. (2018). Altered intestinal microbiota with increased abundance of Prevotella is associated with high risk of diarrhea-predominant irritable bowel syndrome. Gastroenterology Research and Practice, 2018, 6961783. https://doi.org/10.1155/2018/6961783

Więckowska-Deroń, M., Leszcz, M., Bieńko, K., Białek, J., Ćwik-Błotnicka, D., & Borczyk, J. (2023). SIBO—The present knowledge within the contekst of clinical dependencies and therapy. Journal of Education, Health and Sport, 23(1), 22–27. https://doi.org/10.12775/JEHS.2023.23.01.002

Wilk, K., Witkowska, E., Ciechański, M., Cholewiński, S., Wilk, B., Stachura, P., & Kasprzyk, A. (2025). Understanding SIBO: A comprehensive review of causes, symptoms, diagnosis, and treatment strategies of small intestinal bacterial overgrowth. Journal of Education, Health and Sport, 82, 60508. https://doi.org/10.12775/JEHS.2025.82.60508

Wróblewski, H., & Zimna, A. (2021). Use of rifaximin in irritable bowel syndrome treatment. Journal of Education, Health and Sport, 11(8), 247–254. https://doi.org/10.12775/JEHS.2021.11.08.025

Wu, K.-Q., Sun, W.-J., Li, N., Chen, Y.-Q., Wei, Y.-L., & Chen, D.-F. (2019). Small intestinal bacterial overgrowth is associated with diarrhea-predominant irritable bowel syndrome by increasing mainly Prevotella abundance. Annals of Translational Medicine, 7(23), 741. https://doi.org/10.1080/00365521.2019.1694067

Yamini, D., & Pimentel, M. (2008). Irritable bowel syndrome and small intestinal bacterial overgrowth. American Journal of Gastroenterology, 103(12), 3203–3206. https://doi.org/10.1111/j.1572-0241.2008.02258.x

Yang, M., Zhang, L., Hong, G., Li, Y., Li, G., Qian, W., Xiong, H., Bai, T., Song, J., & Hou, X. (2020). Duodenal and rectal mucosal microbiota related to small intestinal bacterial overgrowth in diarrhea-predominant irritable bowel syndrome. Journal of Gastroenterology and Hepatology, 35(5), 795–803. https://doi.org/10.1111/jgh.14910

Zadrozna, K., Wysokińska, O., Małek, A., Iwaniszyn-Zapołoch, K., Wójcik, B., Fabiś, M., & Żyga, J. (2022). Diagnosis and treatment of small intestinal bacterial overgrowth. Journal of Education, Health and Sport, 12(12), 42–48. https://doi.org/10.12775/JEHS.2022.12.12.006

Zhuang, X., Tian, Z., Li, L., Zeng, Z., Chen, M., & Xiong, L. (2018). Fecal microbiota alterations associated with diarrhea-predominant irritable bowel syndrome. Frontiers in Microbiology, 9, 1600. https://doi.org/10.3389/fmicb.2018.01600