Current and Future Approaches for Diagnosing Small Intestinal Dysbiosis in Patients With Symptoms of Functional Dyspepsia

Abstract

The development and application of next generation sequencing technologies for clinical gastroenterology research has provided evidence that microbial dysbiosis is of relevance for the pathogenesis of gastrointestinal and extra-intestinal diseases. Microbial dysbiosis is characterized as alterations of diversity, function, and density of the intestinal microbes. Emerging evidence suggests that alterations of the gastrointestinal microbiome are important for the pathophysiology of a variety of functional gastrointestinal conditions, e.g., irritable bowel syndrome (IBS) and functional dyspepsia (FD), also known as disorders of brain-gut axis interaction. Clinicians have for many years recognized that small intestinal bacterial overgrowth (SIBO) is typified by a microbial dysbiosis that is underpinned by abnormal bacterial loads in these sites. SIBO presents with symptoms which overlap with symptoms of FD and IBS, point toward the possibility that SIBO is either the cause or the consequence of functional gastrointestinal disorders (FGIDs). More recently, new terms including “intestinal methanogen overgrowth” and “small intestinal fungal overgrowth” have been introduced to emphasize the contribution of methane production by archea and fungi in small intestinal dysbiosis. There is emerging data that targeted antimicrobial treatment of SIBO in patients with FD who simultaneously may or may not have IBS, results in symptom improvement and normalization of positive breath tests. However, the association between SIBO and FGIDs remains controversial, since widely accepted diagnostic tests for SIBO are lacking. Culture of jejunal fluid aspirate has been proposed as the “traditional gold standard” for establishing the diagnosis of SIBO. Utilizing jejunal fluid culture, the results can potentially be affected by cross contamination from oropharyngeal and luminal microbes, and there is controversy regarding the best cut off values for SIBO diagnosis. Thus, it is rarely used in routine clinical settings. These limitations have led to the development of breath tests, which when compared with the “traditional gold standard,” have sub-optimal sensitivity and specificity for SIBO diagnosis. With newer diagnostic approaches–based upon applications of the molecular techniques there is an opportunity to characterize the duodenal and colonic mucosa associated microbiome and associated gut microbiota dysbiosis in patients with various gastrointestinal and extraintestinal diseases. Furthermore, the role of confounders like psychological co-morbidities, medications, dietary practices, and environmental factors on the gastrointestinal microbiome in health and disease also needs to be explored.

The duodenal mucosa associated microbiome, visceral sensory function, immune activation and psychological comorbidities in functional gastrointestinal disorders with and without self-reported non-celiac wheat sensitivity

“… 36 , 37 As such and going forward, the clinical definition of “control subjects” and/or collection methods of samples from the proximal small intestine need careful consideration. 38 , 39 …”

Alteración de la microbiota intestinal y su relación con enfermedades gastrointestinales y hepatobiliares

“…Por otra parte, el sobrecrecimiento bacteriano del intestino delgado (SIBO, por sus siglas en inglés, Small Intestinal Bacterial Overgrowth), que es una manifestación de la disbiosis frecuentemente estudiada, puede ser la causa o la consecuencia de los trastornos gastrointestinales funcionales [44]. Para su estudio se utilizan cultivos cuantitativos de aspirado de yeyuno proximal con recuento bacteriano ≥10 5 unidades formadoras de colonias por mL; sin embargo, las pruebas no invasivas como la prueba de aliento con glucosa y la prueba de aliento con lactulosa se han desarrollado para evitar la necesidad del examen endoscópico, y a su vez reducir el costo [22,45].…”

Treatment options for patients with overlap of functional dyspepsia and irritable bowel syndrome

“…Ключові слова: синдром подразненого кишечника, функціональна диспепсія, абдомінальний біль, кишковий мікробіом, олія м'яти перцевої. А. Е. Дорофєєв 1 , С. М. Ткач 2 , Ю. З. Гуркало 1 , Т. Є. Куглер 3 , Ю. В. Жигаль 1 , Ю. В. Чичула [2,5,6].…”

“…Наявність синдрому надмірного бактеріального росту (СНБР) у тонкій кишці є маркером порушень кишкового мікробіому, що посилюються при аномальному бактеріальному навантаженні. Синдром виявляється симптомами, які нагадують симптоми ФД і СПК, що свідчить про те, що СНБР є можливою причиною або наслідком функціональних шлунково-кишкових розладів [5].…”