Small intestinal bacterial overgrowth: current update

Common questions and rationale answers about the intestinal bacterial overgrowth syndrome (SIBO)

The recognition and treatment of intestinal bacterial overgrowth syndrome are matters of controversy. The symptoms that have guided the search for the disorder suffer from lack of specificity, especially in the absence of well-defined predisposing factors. The accuracy of diagnostic procedures has been questioned and the proposed therapies achieve generally low effectiveness figures, with large differences between available studies. It is also unknown whether the normalization of tests is really a guarantee of cure. Within this framework of uncertainty, and in order to contribute to the guidance and homogenization of medical practice, a group of experts from the AEG and ASENEM have formulated the key questions on the management of this pathology and have provided answers to them, in accordance with the available scientific evidence. In addition, they have drawn up statements based on the conclusions of the review and have voted on them individually to reflect the degree of consensus for each statement.

[Small intestine bacterial overgrowth: Myths and realities]

The small intestine bacterial overgrowth (SIBO) is a clinical disorder resulting from colonization of the small intestine by an excessive number of microorganisms or by unusual microorganisms. When they are methane producers it is called intestinal methanogen overgroth (IMO). Known risk factors are congenital or acquired anatomical alterations, motility alterations, some systemic and autoimmune diseases, those that cause alterations in biliopancreatic secretions, hypochlorhydria and some drugs. It causes abdominal pain and distension, bloating, diarrhea, nausea, and weight loss, which can occur in different diseases or with intestinal malabsorption. In IMO there may be constipation. Suggestive analytical data may be iron deficiency, anemia, deficiency of fat-soluble vitamins or B12. The breath test with detection of exhaled H2 is the most accessible technique, but requires rigorous performance and interpretation. The central treatment is oral antibiotics, rifaximin of choice, but they are empirical and should only be prescribed in the event of high clinical suspicion.

A Comprehensive Review of the Usefulness of Prebiotics, Probiotics, and Postbiotics in the Diagnosis and Treatment of Small Intestine Bacterial Overgrowth

Small intestinal bacterial overgrowth (SIBO) is a disorder characterized by the excessive growth of bacteria in the small intestine. Bacterial overgrowth disrupts the bacterial balance and can lead to abdominal pain, weight loss, and gastrointestinal symptoms, including bloating, diarrhea, and malabsorption. SIBO is widespread in the population. There are two main methods for diagnosing SIBO: breath tests and bacterial culture. The most commonly used method is a breath test, which enables the division of SIBO into the following three types: hydrogen-dominant (H-SIBO), methane-dominant (CH4-SIBO), and hydrogen/methane-dominant (H/CH4-SIBO). This comprehensive review aims to present the current knowledge on the use of prebiotics, probiotics, and postbiotics in the context of SIBO. For this purpose, medical databases such as MEDLINE (PubMed) and Scopus were analyzed using specific keywords and their combinations. This review is based on research studies no older than 10 years old and those using only human models. In summary, clinical studies have shown that the efficacy of SIBO therapy can be increased by combining antibiotics with probiotics, especially in vulnerable patients such as children and pregnant women. The further development of diagnostic methods, such as point of care testing (POCT) and portable devices, and a better understanding of the mechanisms of biotics action are needed to treat SIBO more effectively and improve the quality of life of patients.

The Role of the Gastrointestinal Microbiota in Parkinson's Disease

BACKGROUND/OBJECTIVES

Parkinson's disease (PD) is a progressive neurodegenerative disorder characterized by the loss of dopaminergic neurons leading to debilitating motor and non-motor symptoms. Beyond its well-known neurological features, emerging evidence underscores the pivotal role of the gut-brain axis and gastrointestinal microbiota in PD pathogenesis. Dysbiosis has been strongly linked to PD and is associated with increased intestinal permeability, chronic inflammation, and the production of neurotoxic metabolites that may exacerbate neuronal damage.

METHODS

This review delves into the complex interplay between PD and dysbiosis, shedding light on two peculiar subsets of dysbiosis, Helicobacter pylori infection and small-intestinal bacterial overgrowth. These conditions may not only contribute to PD progression but also influence therapeutic responses such as L-dopa efficacy.

CONCLUSIONS

The potential to modulate gut microbiota through probiotics, prebiotics, and synbiotics; fecal microbiota transplantation; and antibiotics represents a promising frontier for innovative PD treatments. Despite this potential, the current evidence is limited by small sample sizes and methodological variability across studies. Rigorous, large-scale, randomized placebo-controlled trials with standardized treatments in terms of composition, dosage, and duration are urgently needed to validate these findings and pave the way for microbiota-based therapeutic strategies in PD management.

Association between small intestine bacterial overgrowth and psychiatric disorders

Small intestinal bacterial overgrowth (SIBO) is a gastrointestinal condition characterized by abnormal colonization of bacteria in the small intestine, leading to overgrowth and alteration, which is linked to gastrointestinal issues, potentially affecting neurological and mental health. Despite existing research, we still do not understand how SIBO affects tryptophan metabolism and psychiatric diseases. We investigated the literature for connections between SIBO, tryptophan metabolism disruptions, and psychiatric disorders like autism, schizophrenia, Alzheimer's, and Parkinson's diseases. We also explored the interaction between thyroid disorders and their influence on SIBO and psychiatric illnesses. PubMed and Google Scholar databases were searched using keywords and phrases, individual and in combinations, like "SIBO," "gut microbiota," "neurologic disorders," "mental disorders," "tryptophan," "dopamine," and "thyroid disease." We focused on original research and review papers that presented empirical studies conducted on animal models and human subjects published in English between February 1992 to February 2023. The initial 2 634 534 records were preliminary screened based on title and abstract and then subjected to full-text review to exclude publications with insufficient data on SIBO, lack of a psychiatric disorder component, or methodological limitations compromising the integrity of the findings. The analysis highlights the significance of the association between psychiatric disorders and SIBO, emphasizing the role of gut-microbial diversity in mental health. We advocate for more detailed studies, including longitudinal research, to clarify the causal relationships between SIBO, gut dysbiosis, and psychiatric disorders and for an integrated approach while treating complex psychiatric conditions.

New Insights into Chronic Pancreatitis: Potential Mechanisms Related to Probiotics

Chronic pancreatitis is a progressive fibroinflammatory disorder with no currently satisfactory treatment. Emerging evidence suggests an association between gut microbial dysbiosis and chronic pancreatitis. Although direct causative evidence is lacking, it is hypothesized that the gut microbiota may play a pivotal role in modulating pancreatic function via the gut-pancreas axis. Thus, modulating the gut microbiota through the administration of probiotics or prebiotics may alleviate pancreatic disorders. In this review, we first propose the potential mechanisms by which specific probiotics or prebiotics may ameliorate chronic pancreatitis, including the alleviation of small intestinal bacterial overgrowth (SIBO), the facilitation of short-chain fatty acids' (SCFAs) production, and the activation of glucagon-like peptide-1 receptors (GLP-1Rs) in the pancreas. Since there are currently no probiotics or prebiotics used for the treatment of chronic pancreatitis, we discuss research in other disease models that have used probiotics or prebiotics to modulate pancreatic endocrine and exocrine functions and prevent pancreatic fibrosis. This provides indirect evidence for their potential application in the treatment of chronic pancreatitis. We anticipate that this research will stimulate further investigation into the gut-pancreas axis and the potential therapeutic value of probiotics and prebiotics in chronic pancreatitis.

Metabolic and Nutritional Issues after Lower Digestive Tract Surgery: The Important Role of the Dietitian in a Multidisciplinary Setting

Many patients undergo small bowel and colon surgery for reasons related to malignancy, inflammatory bowel disease (IBD), mesenteric ischemia, and other benign conditions, including post-operative adhesions, hernias, trauma, volvulus, or diverticula. Some patients arrive in the operating theatre severely malnourished due to an underlying disease, while others develop complications (e.g., anastomotic leaks, abscesses, or strictures) that induce a systemic inflammatory response that can increase their energy and protein requirements. Finally, anatomical and functional changes resulting from surgery can affect either nutritional status due to malabsorption or nutritional support (NS) pathways. The dietitian providing NS to these patients needs to understand the pathophysiology underlying these sequelae and collaborate with other professionals, including surgeons, internists, nurses, and pharmacists. The aim of this review is to provide an overview of the nutritional and metabolic consequences of different types of lower gastrointestinal surgery and the role of the dietitian in providing comprehensive patient care. This article reviews the effects of small bowel resection on macronutrient and micronutrient absorption, the effects of colectomies (e.g., ileocolectomy, low anterior resection, abdominoperineal resection, and proctocolectomy) that require special dietary considerations, nutritional considerations specific to ostomized patients, and clinical practice guidelines for caregivers of patients who have undergone a surgery for local and systemic complications of IBD. Finally, we highlight the valuable contribution of the dietitian in the challenging management of short bowel syndrome and intestinal failure.

Diagnosis and management of pancreatic insufficiency in patients with gastrectomy due to cancer or gastric ulcers: a virtual roundtable expert discussion

INTRODUCTION

Pancreatic exocrine insufficiency (PEI) is common after gastric resection for cancer or ulcers but is under-recognized and undertreated. Although pancreatic enzyme replacement therapy (PERT) is the mainstay of PEI management, robust evidence supporting its use after gastric surgery is limited.

AREAS COVERED

In the absence of guideline recommendations specific for patients with pancreatic insufficiency after gastrectomy, a panel of experts from different geographical regions convened in a virtual meeting to discuss their approach to patient management.

EXPERT OPINION

Pancreatic insufficiency after gastrointestinal surgery is not a simple post-surgical complication as several factors contribute to its development. Although the pancreas is unimpaired after gastrectomy, it cannot function normally in the altered environment. Pancreatic insufficiency can be challenging to diagnose in gastrectomy patients due to nonspecific symptoms and the absence of a simple diagnostic test. Fecal elastase appears to be the default test, although it is not sufficiently sensitive nor reliable for diagnosing or monitoring PEI. Patients with maldigestion symptoms after gastrectomy are treated pragmatically: those with clinical suspicion of pancreatic insufficiency receive a trial of PERT and are monitored for symptom improvement. There is a clear need for high-quality evidence from clinical trials to guide the management of this patient population.

Gut Microbiota and Bacterial Translocation in the Pathogenesis of Liver Fibrosis

Cirrhosis is the end result of liver fibrosis in chronic liver diseases. Studying the mechanisms of its development and developing measures to slow down and regress it based on this knowledge seem to be important tasks for medicine. Currently, disorders of the gut-liver axis have great importance in the pathogenesis of cirrhosis. However, gut dysbiosis, which manifests as increased proportions in the gut microbiota of Bacilli and Proteobacteria that are capable of bacterial translocation and a decreased proportion of Clostridia that strengthen the intestinal barrier, occurs even at the pre-cirrhotic stage of chronic liver disease. This leads to the development of bacterial translocation, a process by which those microbes enter the blood of the portal vein and then the liver tissue, where they activate Kupffer cells through Toll-like receptor 4. In response, the Kupffer cells produce profibrogenic cytokines, which activate hepatic stellate cells, stimulating their transformation into myofibroblasts that produce collagen and other elements of the extracellular matrix. Blocking bacterial translocation with antibiotics, probiotics, synbiotics, and other methods could slow down the progression of liver fibrosis. This was shown in a number of animal models but requires further verification in long-term randomized controlled trials with humans.