A systematic review of diagnostic tests for small intestinal bacterial overgrowth

Small Intestinal Bacterial Overgrowth: Nutritional Implications, Diagnosis, and Management

Small intestinal bacterial overgrowth (SIBO), characterized by the presence of excessive bacteria in the small intestine, is typically described as a malabsorptive syndrome occurring in the context of gut stasis syndromes. SIBO is now considered to be a disorder associated with diverse clinical conditions without classic risk factors for SIBO and a cause of several nonspecific gastrointestinal and nongastrointestinal symptoms. Because there is currently no gold standard for diagnosing SIBO, its prevalence and role in the pathogenesis of other diseases remain uncertain; as does optimal treatment of patients with relapsing symptoms.

Nutritional Interventions in Chronic Intestinal Pseudoobstruction

Although chronic intestinal pseudo-obstruction (CIPO) is a rare disorder, it presents a wide spectrum of severity that ranges from abdominal bloating to severe gastrointestinal dysfunction. In the worst cases, patients may become dependent upon artificial nutrition via parenteral nutrition or choose to have an intestinal transplant. However, whatever the severity, a patient's quality of life can be seriously compromised. This article defines the disorder and discusses the spectrum of disease and challenges to providing adequate nutrition to help improve a patient's quality of life.

Celiac Disease and Other Causes of Duodenitis

CONTEXT

- Patients who receive an upper gastrointestinal endoscopic examination frequently have biopsies taken from the duodenum. Accurate interpretation of duodenal biopsies is essential for patient care. Celiac disease is a common clinical concern, but pathologists need to be aware of other conditions of the duodenum that mimic celiac disease.

OBJECTIVE

- To review the normal histologic features of duodenal mucosa and describe the clinical and histologic findings in celiac disease and its mimics, listing the differentiating features of biopsies with villous atrophy and epithelial lymphocytosis.

DATA SOURCES

- The study comprises a literature review of pertinent publications as of November 30, 2016.

CONCLUSIONS

- Celiac disease is a common cause of abnormal duodenal histology. However, many of the histologic features found in the duodenal biopsy of patients with celiac disease are also present in other conditions that affect the small bowel. Diagnostic precision may be enhanced by obtaining a careful patient history and by ancillary laboratory testing, particularly for the presence of antitissue transglutaminase antibodies.

Diet and rosacea: the role of dietary change in the management of rosacea

Dietary change may play a role in the therapy of rosacea. Certain foods and beverages may act as "triggers" for rosacea exacerbations. These may be divided into heat-related, alcohol-related, capsaicin-related, and cinnamaldehyde-related. One potential pathogenic mechanism may be via the activation of transient receptor potential cation channels, which result in neurogenic vasodilatation. Further research is needed on the role of the gut skin connection in rosacea. Epidemiologic studies suggest that patients with rosacea have a higher prevalence of gastrointestinal disease, and one study reported improvement in rosacea following successful treatment of small intestinal bacterial overgrowth. While further research is required in this area, patients may be advised on measures to support a healthy gut microbiome, including the consumption of a fiber-rich (prebiotic) diet.

Clinical and Histologic Mimickers of Celiac Disease

Celiac disease is an autoimmune disorder of the small bowel, classically associated with diarrhea, abdominal pain, and malabsorption. The diagnosis of celiac disease is made when there are compatible clinical features, supportive serologic markers, representative histology from the small bowel, and response to a gluten-free diet. Histologic findings associated with celiac disease include intraepithelial lymphocytosis, crypt hyperplasia, villous atrophy, and a chronic inflammatory cell infiltrate in the lamina propria. It is important to recognize and diagnose celiac disease, as strict adherence to a gluten-free diet can lead to resolution of clinical and histologic manifestations of the disease. However, many other entities can present with clinical and/or histologic features of celiac disease. In this review article, we highlight key clinical and histologic mimickers of celiac disease. The evaluation of a patient with serologically negative enteropathy necessitates a carefully elicited history and detailed review by a pathologist. Medications can mimic celiac disease and should be considered in all patients with a serologically negative enteropathy. Many mimickers of celiac disease have clues to the underlying diagnosis, and many have a targeted therapy. It is necessary to provide patients with a correct diagnosis rather than subject them to a lifetime of an unnecessary gluten-free diet.

Small intestinal bacterial overgrowth as a cause for irritable bowel syndrome: guilty or not guilty?

PURPOSE OF REVIEW

Small intestinal bacterial overgrowth (SIBO) has been proposed as a cause of irritable bowel syndrome (IBS). However, this relationship has been subject to controversy. This review aims to provide a current perspective on the SIBO-IBS hypothesis.

RECENT FINDINGS

Case-control studies evaluating the prevalence of SIBO in IBS and healthy individuals have shown conflicting results. Moreover, the tests available in routine clinical practice to diagnose SIBO are not valid and lack both sensitivity and specificity. Hence, interpreting the effect of interventions based on these tests is fraught with uncertainty. Furthermore, the SIBO-IBS hypothesis has paved the way to assess antibiotic therapy in nonconstipated IBS, with rifaximin, a nonabsorbable antibiotic, showing modest but significant clinical benefit. However, individuals were not tested for SIBO and the mechanism of action of rifaximin in IBS remains to be elucidated. Preliminary data suggest that rifaximin decreases microbial richness and previous studies have noted antibacterial interventions in IBS to reduce colonic fermentation and improve symptoms. The advent of rapid culture-independent molecular techniques is a promising tool that will seek to clarify and advance our understanding of the gut microbial function.

SUMMARY

The SIBO-IBS hypothesis lacks convincing evidence but remains under scrutiny. The mechanism resulting in symptom improvement after rifaximin treatment in some IBS individuals requires exploration. Novel molecular techniques provide an exciting and challenging opportunity to explore the host-gut microbiota interaction.

Hydrogen and Methane-Based Breath Testing in Gastrointestinal Disorders: The North American Consensus

OBJECTIVES

Breath tests (BTs) are important for the diagnosis of carbohydrate maldigestion syndromes and small intestinal bacterial overgrowth (SIBO). However, standardization is lacking regarding indications for testing, test methodology and interpretation of results. A consensus meeting of experts was convened to develop guidelines for clinicians and research.

METHODS

Pre-meeting survey questions encompassing five domains; indications, preparation, performance, interpretation of results, and knowledge gaps, were sent to 17 clinician-scientists, and 10 attended a live meeting. Using an evidence-based approach, 28 statements were finalized and voted on anonymously by a working group of specialists.

RESULTS

Consensus was reached on 26 statements encompassing all five domains. Consensus doses for lactulose, glucose, fructose and lactose BT were 10, 75, 25 and 25 g, respectively. Glucose and lactulose BTs remain the least invasive alternatives to diagnose SIBO. BT is useful in the diagnosis of carbohydrate maldigestion, methane-associated constipation, and evaluation of bloating/gas but not in the assessment of oro-cecal transit. A rise in hydrogen of ≥20 p.p.m. by 90 min during glucose or lactulose BT for SIBO was considered positive. Methane levels ≥10 p.p.m. was considered methane-positive. SIBO should be excluded prior to BT for carbohydrate malabsorption to avoid false positives. A rise in hydrogen of ≥20 p.p.m. from baseline during BT was considered positive for maldigestion.

CONCLUSIONS

BT is a useful, inexpensive, simple and safe diagnostic test in the evaluation of common gastroenterology problems. These consensus statements should help to standardize the indications, preparation, performance and interpretation of BT in clinical practice and research.

Probiotics for Preventing and Treating Small Intestinal Bacterial Overgrowth: A Meta-Analysis and Systematic Review of Current Evidence

The present study conducted a meta-analysis and systematic review of current evidence to assess the efficacy of probiotics in preventing or treating small intestinal bacterial overgrowth (SIBO). Relevant studies from PubMed, Embase, and the Cochrane Central Register of Controlled Trials, until May 2016, were assimilated. The prevention efficacy was assessed by the incidence of SIBO in the probiotic group, and the treatment efficacy by the SIBO decontamination rate, reduction in H2 concentration, and symptom improvement. The relative risk (RR) and weighted mean difference (WMD) were used as effect measures and the random-effects model used for meta-analysis. A total of 14 full-text articles and 8 abstracts were included for the systematic review, and 18 studies were eligible for data synthesis. Patients on probiotic usage showed an insignificant trend toward low SIBO incidence [RR=0.54; 95% confidence intervals (CI), 0.19-1.52; P=0.24]. The pooled SIBO decontamination rate was 62.8% (51.5% to 72.8%). The probiotics group showed a significantly higher SIBO decontamination rate than the nonprobiotic group (RR=1.61; 95% CI, 1.19-2.17; P<0.05). Also, the H2 concentration was significantly reduced among probiotic users (WMD=-36.35 ppm; 95% CI, -44.23 to -28.47 ppm; P<0.05). Although probiotics produced a marked decrease in the abdominal pain scores (WMD=-1.17; 95% CI, -2.30 to -0.04; P<0.05), it did not significantly reduce the daily stool frequency (WMD=-0.09; 95% CI, -0.47 to 0.29). Therefore, the present findings indicated that probiotics supplementation could effectively decontaminate SIBO, decrease H2 concentration, and relieve abdominal pain, but were ineffective in preventing SIBO.

Systematic review with meta-analysis: rifaximin is effective and safe for the treatment of small intestine bacterial overgrowth

BACKGROUND

Small intestinal bacterial overgrowth (SIBO) is a heterogeneous syndrome, characterised by an increased number and/or abnormal type of bacteria in the small bowel. Over the past decades, rifaximin has gained popularity for this indication despite its use is not evidence based.

AIM

To perform a systematic review and meta-analysis to summarise evidence about the efficacy and safety of rifaximin to eradicate SIBO in adult patients.

METHODS

MEDLINE, EMBASE, CCRCT, Scopus and Web of Science were searched from inception to March 16, 2015 for RCTs and observational studies. Furthermore, abstract books of major European, American and Asian gastroenterological meetings were also examined.

RESULTS

Thirty-two studies involving 1331 patients were included. The overall eradication rate according to intention-to-treat analysis was 70.8% (95% CI: 61.4-78.2; I² = 89.4%) and to per protocol analysis 72.9% (95% CI: 65.5-79.8; I² = 87.5%). Meta-regression identified three covariates (drug dose, study design and co-therapy) independently associated with an increased eradication rate. The overall rate of adverse events was 4.6% (95% CI: 2.3-7.5; I² = 63.6%). In the subset of studies (n= 10) allowing the analysis, improvement or resolution of symptoms in patients with eradicated SIBO was found to be 67.7% (95% CI: 44.7-86.9; I² = 91.3%).

CONCLUSIONS

Rifaximin treatment seems to be effective and safe for the treatment of SIBO. However, the quality of the available studies is generally poor. Well-designed RCTs are needed to substantiate these findings and to establish the optimal regimen.

Small Intestinal Bacterial Overgrowth and Other Intestinal Disorders

Gut microbiota is the largest organ of the human body. Although growth of bacteria more than 10⁵ colony forming unit (CFU) per milliliter in culture of upper gut aspirate is used to diagnosis small intestinal bacterial overgrowth (SIBO), 10³ CFU or more is being considered to suggest the diagnosis, particularly if colonic type bacteria are present in the upper gut. Although neither very sensitive nor specific, hydrogen breath tests are widely used to diagnose SIBO. Rifaximin is the best treatment for SIBO due to its broad spectrum, lack of systemic absorption, and safety profile.

PREVALENCE OF SMALL INTESTINE BACTERIAL OVERGROWTH IN PATIENTS WITH GASTROINTESTINAL SYMPTOMS

BACKGROUND

Small intestine bacterial overgrowth is a heterogeneous syndrome characterized by an increase in the number and/or the presence of atypical microbiota in the small intestine. The symptoms of small intestine bacterial overgrowth are unspecific, encompassing abdominal pain/distension, diarrhea and flatulence. Due to the increased cost and complexity for carrying out the jejunal aspirate, the gold standard for diagnosis of the syndrome, routinely the hydrogen (H 2 ) breath test has been used, utilizing glucose or lactulose as substrate, which is able to determine, in the exhaled air, the H 2 concentration produced from the intestinal bacterial metabolism. However, due to a number of individuals presenting a methanogenic microbiota, which does not produce H 2 , the testing on devices capable of detecting, concurrently, the concentration of exhaled H 2 and methane (CH 4 ) is justified.

OBJECTIVE

This study aimed to determine the prevalence of small intestine bacterial overgrowth in patients with digestive symptoms, through a comparative analysis of breath tests of H 2 or H 2 and CH 4 associated, using glucose as substrate .

METHODS

A total of 200 patients of both sexes without age limitation were evaluated, being directed to a Breath Test Laboratory for performing the H 2 test (100 patients) and of exhaled H 2 and CH 4 (100 patients) due to gastrointestinal complaints, most of them patients with gastrointestinal functional disorders.

RESULTS

The results indicated a significant prevalence of small intestine bacterial overgrowth in the H 2 test and in the test of exhaled H 2 and CH 4 (56% and 64% respectively) in patients with gastrointestinal symptoms, and higher prevalence in females. It found further that methane gas was alone responsible for positivity in 18% of patients.

CONCLUSION

The data found in this study is consistent with the findings of the current literature and underscores the need for using devices capable of capturing the two gases (exhaled H 2 and CH 4 ) to improve the sensitivity and hence the accuracy of small intestine bacterial overgrowth diagnosis in daily medical practice.

Small Intestinal Bacterial Overgrowth: A Primary Care Review

Gastrointestinal symptoms are commonly seen in the primary care setting.¹ These patient presentations can be nonspecific, leading to a broad differential diagnosis. Small intestinal bacterial overgrowth is a clinical entity that can present with many of these nonspecific gastrointestinal symptoms. The recent interest in the microbiome by those in the medical and lay communities has made this syndrome all the more relevant. This review gives the primary care provider an up-to-date understanding of the etiology, risk factors and predisposing factors, presentation, diagnostic testing, and management of small intestinal bacterial overgrowth.

Testing for Chronic Diarrhea

Chronic diarrhea is a frequently encountered symptom in clinical practice. The etiologies for chronic diarrhea are diverse and broad with varying clinical implications. A useful method of categorizing chronic diarrhea to guide a diagnostic work-up is a pathophysiology-based framework. Chronic diarrhea may be categorized as malabsorptive, secretory, osmotic, and inflammatory or motility related. Frequently, overlap between categories may exist for any given diarrhea etiology and diagnostic testing must occur with an understanding of the differential diagnosis. Investigations to achieve a diagnosis for chronic diarrhea range from screening blood and stool tests to more directed testing such as diagnostic imaging, and endoscopic and histological evaluation. The pathophysiology-based framework proposed in this chapter will allow the clinician to select screening tests followed by targeted tests to minimize cost and complications to the patient, while providing a highly effective method to achieve an accurate diagnosis.

Diagnosis and treatment of small intestinal bacterial overgrowth

A huge number of bacteria are hosted in the gastrointestinal tract, following a gradient increasing towards the colon. Gastric acid secretion and intestinal clearance provide the qualitative and quantitative partitioning of intestinal bacteria; small intestinal bacteria overgrowth (SIBO) occurs when these barrier mechanisms fail. Diagnosis of SIBO is challenging due to the low specificity of symptoms, the frequent association with other diseases of the gastrointestinal tract and the absence of optimal objective diagnostic tests. The therapeutic approach to SIBO is oriented towards resolving predisposing conditions, and is supported by antibiotic treatment to restore the normal small intestinal microflora and by modifications of dietary habits for symptomatic relief. In the near future, metagenomics and metabolomics will help to overcome the uncertainties of SIBO diagnosis and the pitfalls of therapeutic management, allowing the design of a personalized strategy based on the direct insight into the small intestinal microbial community.

Insulin resistance alters hepatic ethanol metabolism: studies in mice and children with non-alcoholic fatty liver disease

OBJECTIVE

Increased fasting blood ethanol levels, suggested to stem from an increased endogenous ethanol synthesis in the GI tract, are discussed to be critical in the development of non-alcoholic fatty liver disease (NAFLD). The aim of the present study was to further delineate the mechanisms involved in the elevated blood ethanol levels found in patients with NAFLD.

DESIGN

In 20 nutritionally and metabolically screened children displaying early signs of NAFLD and 29 controls (aged 5-8 years), ethanol plasma levels were assessed. Ethanol levels along the GI tract, in vena cava and portal vein, intestinal and faecal microbiota, and activity of alcohol dehydrogenase (ADH) and cytochrome P450 2E1 (CYP2E1) were measured in wild-type, ob/ob and anti-TNFα antibody (aT) treated ob/ob mice.

RESULTS

Despite not differing in dietary pattern or prevalence of intestinal overgrowth, fasting ethanol levels being positively associated with measures of insulin resistance were significantly higher in children with NAFLD than in controls. Ethanol levels were similar in portal vein and chyme obtained from different parts of the GI tract between groups while ethanol levels in vena cava plasma were significantly higher in ob/ob mice. ADH activity was significantly lower in liver tissue obtained from ob/ob mice in comparison to wild-type controls and ob/ob mice treated with aT.

CONCLUSIONS

Taken together, our data of animal experiments suggest that increased blood ethanol levels in patients with NAFLD may result from insulin-dependent impairments of ADH activity in liver tissue rather than from an increased endogenous ethanol synthesis.

TRIAL REGISTRATION NUMBER

NCT01306396.

Refining small intestinal bacterial overgrowth diagnosis by means of carbohydrate specificity: a proof-of-concept study

BACKGROUND

Diagnosis of small intestinal bacterial overgrowth (SIBO) remains challenging. This study aimed at proving the diagnostic concept of carbohydrate-specific SIBO (cs-SIBO) using glucose, fructose and sorbitol hydrogen (H2)/methane (CH4) breath testing (HMBT).

METHODS

In this study 125 patients referred to our outpatient clinic for SIBO testing were included. All individuals underwent glucose (50 g), fructose (25 g) and sorbitol (12.5 g) HMBT at 3 consecutive days. Patients with cs-SIBO (i.e. early H2/CH4 peak) were given rifaximin (600 mg/day) in a 10-day treatment. HMBT results were reassessed in a subset of patients 3-6 months after antibiotic therapy. In view of cs-SIBO diagnosis, agreements between HMBT results obtained for different sugars were calculated using Cohen's kappa (κ) with 95% confidence intervals (CIs).

RESULTS

A total of 59 (47.2%) patients presented an early H2/CH4 peak with one or more sugars. Among these, 21 (16.8%), 10 (8.0%) and 7 (5.6%) individuals had a positive HMBT result with either glucose, fructose or sorbitol, respectively. Another 21 (16.8%) patients with a positive glucose HMBT result were also found positive with an early H2/CH4 peak obtained after ingestion of fructose and/or sorbitol. Fair agreement was observed between glucose and fructose (κ = 0.26, p = 0.0018) and between glucose and sorbitol (κ = 0.18, p = 0.0178) HMBT results. Slight agreement was observed between fructose and sorbitol (κ = 0.03, p = 0.6955) HMBT results only. Successful antibiotic therapy with rifaximin could be demonstrated in 26/30 (86.7%) of patients as indicated by normal HMBT results and symptom remission.

CONCLUSIONS

Combined glucose, fructose and sorbitol HMBT has the potential to optimize cs-SIBO diagnosis. Furthermore, the majority of patients with cs-SIBO seem to benefit from rifaximin therapy regardless of its carbohydrate specificity.

Lactulose Hydrogen Breath Test Result Is Associated with Age and Gender

Small intestinal bacterial overgrowth (SIBO) is associated with chronic gastrointestinal diseases and structural/functional abnormalities of the gastrointestinal tract. SIBO's association with clinical characteristics is unclear. This study investigates the association between clinical factors and SIBO according to lactulose hydrogen breath test (LHBT) result. Methods. A cross-sectional study in a university-based gastroenterology practice was performed. Data was abstracted from the medical records of subjects undergoing LHBT from 6/1/2009 to 6/1/2013. Logistic regression analysis was performed to determine the association between predictor variables: age, sex, body mass index (BMI), and positive LHBT, the outcome of interest. Results. LHBT was performed in 791 subjects. Fifty-four percent had a positive LHBT. There was no statistically significant difference between the LHBT results according to age or BMI. In females, the likelihood of a positive LHBT increased with age (OR 1.02; 95% CI: 1.01–1.03). In males, the likelihood of a positive LHBT result decreased with age (OR 0.98; 95% CI: 0.97–1.00). Conclusion. There was an association between age, with respect to sex, and a positive LHBT. With increased age in females, the odds of a positive LHBT increased, while, in men, the odds of a positive LHBT decreased with age.

Breath Testing for Small Intestinal Bacterial Overgrowth: Should We Bother?

The hydrogen breath test is based on following breath hydrogen levels after the administration of a carbohydrate (most commonly lactulose) to a patient with suspected small intestinal bacterial overgrowth. The test is based on the interaction between the administered carbohydrate and the intestinal bacteria. The resulting fermentation produces hydrogen. A positive breath test is based on a breath hydrogen rise prior to the expected arrival time in the highly microbial cecum. Despite renewed enthusiasm for breath testing in recent years due to associations with conditions such as irritable bowel syndrome, breath testing poses many challenges. In this argument against breath testing, several pitfalls that complicate breath testing will be described.

How to Test and Treat Small Intestinal Bacterial Overgrowth: an Evidence-Based Approach

Small intestinal bacterial overgrowth (SIBO) is characterized by an excessive amount of bacteria in the small intestine and a constellation of symptoms that include bloating, pain, gas, and diarrhea. Although known for many decades, there is a lack of consensus and clarity regarding the natural history and methods for its diagnosis. Several tests have been proposed, including the glucose breath test, lactulose breath test, small intestinal aspiration and culture, and others. However, there is a lack of standardization of these tests and their interpretation. Treatment of SIBO remains empirical; generally, broad spectrum antibiotics are recommended for 2 weeks (amoxicillin, rifaximin, ciprofloxacin, etc.) but evidence for their use is fair. Clearly, there is a strong need to develop a systematic approach for the management of SIBO and to perform multicenter clinical trials for the treatment of SIBO. In this review, we will discuss the current evidence for the diagnosis and treatment of SIBO, which includes (1) elimination/modification of the underlying causes, (2) induction of remission (antibiotics and elemental diet), and (3) maintenance of remission (promotility drugs, dietary modifications, repeat or cyclical antibiotics).

Review article: potential mechanisms of action of rifaximin in the management of irritable bowel syndrome with diarrhoea

BACKGROUND

The role of gut microbiota in the pathophysiology of irritable bowel syndrome (IBS) is supported by various lines of evidence, including differences in mucosal and faecal microbiota between patients with IBS and healthy individuals, development of post-infectious IBS, and the efficacy of some probiotics and nonsystemic antibiotics (e.g. rifaximin).

AIM

To review the literature regarding the role of rifaximin in IBS and its potential mechanism(s) of action.

METHODS

A literature search was conducted using the terms 'rifaximin', 'irritable bowel syndrome' and 'mechanism of action'.

RESULTS

Rifaximin was approved in 2015 for the treatment of IBS with diarrhoea. In contrast to other currently available IBS therapies that require daily administration to maintain efficacy, 2-week rifaximin treatment achieved symptom improvement that persisted ≥12 weeks post-treatment. The mechanisms of action of rifaximin, therefore, may extend beyond direct bactericidal effects. Data suggest that rifaximin may decrease host proinflammatory responses to bacterial products in patients with IBS. In some cases, small intestinal bacterial overgrowth (SIBO) may play a role in the clinical symptoms of IBS. Because of the high level of solubility of rifaximin in the small intestine, rifaximin may reset microbial diversity in this environment. Consistent with this hypothesis, rifaximin has antibiotic efficacy against isolates derived from patients with SIBO.

CONCLUSION

Resetting microbial diversity via rifaximin use may lead to a decrease in bacterial fermentation and a reduction in the clinical symptoms of IBS.

Buserelin treatment to rats causes enteric neurodegeneration with moderate effects on CRF-immunoreactive neurons and Enterobacteriaceae in colon, and in acetylcholine-mediated permeability in ileum

Background

The gonadotropin-releasing hormone (GnRH) analog buserelin causes enteric neuronal loss. Acute stress or injection of corticotropin-releasing factor (CRF) affects motility, secretion, and barrier function of the gastrointestinal tract. The aim of the study was to characterize the CRF immunoreactivity in enteric neurons after buserelin treatment, and to evaluate possible effects of enteric neuropathy on gut microbiota, intestinal permeability, and stress response behavior.

Results

Sixty rats were given buserelin (20 μg) or saline subcutaneously for 5 days, repeated four times with 3 weeks in-between. At the study end, enteric neuronal density, enteric expression of CRF, gut microbial composition, and plasma levels of adrenocorticotropic hormone (ACTH) and CRF were analyzed. Intestinal permeability was examined in Ussing chambers and the reaction to stressful events was measured by behavior tests. Buserelin treatment reduced the number of neurons along the entire gastrointestinal tract, with increased relative numbers of CRF-immunoreactive submucosal and myenteric neurons in colon (p < 0.05 and p < 0.01, respectively). The overall microbial diversity and relative abundance did not differ between groups, but Enterobacteriaceae was decreased in colon in buserelin-treated rats (p = 0.020). Basal intestinal permeability did not differ between groups, whereas carbachol stimulation increased ileum permeability in controls (p < 0.05), but not in buserelin-treated rats. Buserelin did not affect stress behavior.

Conclusions

Although buserelin treatment leads to enteric neuronal loss along the gastrointestinal tract with an increased percentage of CRF-immunoreactive neurons in colon, the physiology is well preserved, with modest effects on colon microbiota and absence of carbachol-induced permeability in ileum as the only observed changes.

Electronic supplementary material

The online version of this article (doi:10.1186/s13104-015-1800-x) contains supplementary material, which is available to authorized users.

Contributions of microbiome and mechanical deformation to intestinal bacterial overgrowth and inflammation in a human gut-on-a-chip

A human gut-on-a-chip microdevice was used to coculture multiple commensal microbes in contact with living human intestinal epithelial cells for more than a week in vitro and to analyze how gut microbiome, inflammatory cells, and peristalsis-associated mechanical deformations independently contribute to intestinal bacterial overgrowth and inflammation. This in vitro model replicated results from past animal and human studies, including demonstration that probiotic and antibiotic therapies can suppress villus injury induced by pathogenic bacteria. By ceasing peristalsis-like motions while maintaining luminal flow, lack of epithelial deformation was shown to trigger bacterial overgrowth similar to that observed in patients with ileus and inflammatory bowel disease. Analysis of intestinal inflammation on-chip revealed that immune cells and lipopolysaccharide endotoxin together stimulate epithelial cells to produce four proinflammatory cytokines (IL-8, IL-6, IL-1β, and TNF-α) that are necessary and sufficient to induce villus injury and compromise intestinal barrier function. Thus, this human gut-on-a-chip can be used to analyze contributions of microbiome to intestinal pathophysiology and dissect disease mechanisms in a controlled manner that is not possible using existing in vitro systems or animal models.

Irritable bowel syndrome: Is it "irritable brain" or "irritable bowel"?

Irritable bowel syndrome (IBS) has been recognized as one of the most common and best studied disorders among the group of functional gastrointestinal disorders. It is a functional bowel disorder in which abdominal pain or discomfort is associated with defecation or a change in bowel habit. In the Western world, IBS appears to affect up to 20% of the population at any given time but in Asian countries, the median value of IBS prevalence defined by various criteria ranges between 6.5% and 10.1%, and community prevalence of 4% is found in North India. Those attending gastroenterology clinics represent only the tip of the iceberg. The disorder substantially impairs the quality of life, and the overall health-care costs are high. IBS has therefore gained increased attention from clinicians, researchers, and pharmaceutical industries. It is often frustrating to both patients and physicians as the disease is usually chronic in nature and difficult to treat. However, the understanding of IBS has been changing from time to time and still most of its concepts are unknown. In this review we have discussed, debated, and synthesized the evidence base, focusing on underlying mechanisms in the brain and bowel. We conclude that it is both brain and bowel mechanisms that are responsible. The clinical implication of such mechanisms is discussed.

Small intestinal bacterial overgrowth: duodenal aspiration vs glucose breath test

BACKGROUND

The diagnosis of small intestinal bacterial overgrowth (SIBO) remains challenging. Our aim was to examine the diagnostic yield of duodenal aspiration/culture and glucose breath test (GBT), and effects of gender, race and demographics on prevalence of SIBO.

METHODS

Patients with unexplained gas, bloating and diarrhea and negative endoscopy, imaging and blood tests were prospectively enrolled in two centers in USA. Randomly, within 1 week each patient underwent both duodenal aspiration/culture and GBT. The diagnostic yield of each test and relationship of symptoms, and effects of ethnicity, age, and gender on prevalence of SIBO were assessed and compared.

KEY RESULTS

Duodenal culture was positive in 62/139 (44.6%) subjects and GBT was positive in 38/139 (27.3%) subjects with an overall diagnostic agreement of 65.5%. The sensitivity, specificity, positive and negative predictive value of GBT was 42%, 84%, 68%, and 64%, respectively. Ethnicity or gender did not influence SIBO, but SIBO positive patients were older (p = 0.0018). Symptom patterns were similar except bloating was more prevalent in GBT positive and gas in culture positive subjects.

CONCLUSIONS & INFERENCES

Duodenal aspiration/culture identifies 45% of patients with suspected SIBO. GBT has lower sensitivity but good specificity for detection of SIBO. There were no ethnic or gender differences in the prevalence of SIBO, but patients with SIBO were older. Because GBT is non-invasive, it should be considered first in patients with suspected SIBO.

[Characterization, influence and manipulation of the gastrointestinal microbiota in health and disease]

The gastrointestinal tract harbors trillions of microorganisms that are indispensable for health. The gastrointestinal microbiota can be studied using culture and molecular methods. The applications of massive sequencing are constantly increasing, due to their high yield, increasingly accessible costs, and the availability of free software for data analysis. The present article provides a detailed review of a large number of studies on the gastrointestinal microbiota and its influence on human health; particular emphasis is placed on the evidence suggesting a relationship between the gastrointestinal microbial ecosystem and diverse physiological and immune/inflammatory processes. Discussion of the articles analyzed combines a medical approach and current concepts of microbial molecular ecology. The present revision aims to be useful to those interested in the gastrointestinal microbiota and its possible alteration to maintain, re-establish and enhance health in the human host.

Small intestinal bacterial overgrowth syndrome in children

Introduction

Small intestinal bacterial overgrowth syndrome (SIBO) is defined as an increased number of nonpathogenic bacteria over 10⁵ organisms in 1 millilitre of small intestine content. The most common predisposing factors include, among others, gut motility disorders and chronic use of proton pump inhibitors. The results of recent studies indicate the importance of SIBO in gastrointestinal diseases.

Aim

To assess the prevalence of SIBO in children with abdominal pain.

Material and methods

One hundred children (59 girls and 41 boys) aged from 4 to 17 years (mean age: 10.47 ±3.73 years), hospitalised due to abdominal pain, were enrolled in the study. Hydrogen breath test (HBT) with lactulose was established among all patients. Expired air was analysed using a Gastrolyzer (Bedfont).

Results

The HBT result was positive in 63 (63%) children with abdominal pain; including 40 girls (67.8%) and 23 boys (56.1%). The test was positive in the group of 29 (46%) children aged under 10 years and in the group of 34 (54%) children aged over 10 years. Among the patients who reported for the control study 88% achieved a normalisation of HBT after treatment.

Conclusions

The prevalence of positive HBT results in the group of patients with abdominal pain is over 60%. Small intestinal bacterial overgrowth syndrome should be considered as one of the causes of abdominal pain in children. The SIBO in children shows a good response to treatment.

Intestinal Microbiome, Small Intestinal Bacterial Overgrowth and Inflammatory Bowel Diseases - What are the Connections?

IBD (inflammatory bowel diseases) represent chronic idiopathic inflammatory diseases, prone to relapse in the digestive tract; it is estimated that they result from the interaction of the intestinal microbiome with the intestinal immune system. The inflammatory microbiome exerts multiple beneficial roles. Perhaps the central element to developing IBD is dysbiosis; there is still an incompletely established association between intestinal microbiome changes in patients with IBD and SIBO (small intestinal bacterial overgrowth). Influencing the intestinal microbiome may play an adjuvant therapeutic role in the treatment of IBD. We present a synthesis of the connections between the entities mentioned above.

Duodenal Aspirates for Small Intestine Bacterial Overgrowth: Yield, PPIs, and Outcomes after Treatment at a Tertiary Academic Medical Center

Duodenal aspirates are not commonly collected, but they can be easily used in detection of small intestinal bacterial overgrowth (SIBO). Proton pump inhibitor (PPI) use has been proposed to contribute to the development of SIBO. We aimed to determine the yield of SIBO-positive cultures detected in duodenal aspirates, the relationship between SIBO and PPI use, and the clinical outcomes of patients identified by this method. In a retrospective study, we analyzed electronic medical records from 1263 consecutive patients undergoing upper endoscopy at a tertiary medical center. Aspirates were collected thought out the third and fourth portions of the duodenum, and cultures were considered to be positive for SIBO if they produced more than 100,000 cfu/mL. Culture analysis of duodenal aspirates identified SIBO in one-third of patients. A significantly higher percentage of patients with SIBO use PPIs than patients without SIBO, indicating a possible association. Similar proportions of patients with SIBO improved whether or not they received antibiotic treatment, calling into question the use of this expensive therapy for this disorder.

Guidance on the management of diarrhoea during cancer chemotherapy

Diarrhoea induced by chemotherapy in cancer patients is common, causes notable morbidity and mortality, and is managed inconsistently. Previous management guidelines were based on poor evidence and neglect physiological causes of chemotherapy-induced diarrhoea. In the absence of level 1 evidence from randomised controlled trials, we developed practical guidance for clinicians based on a literature review by a multidisciplinary team of clinical oncologists, dietitians, gastroenterologists, medical oncologists, nurses, pharmacist, and a surgeon. Education of patients and their carers about the risks associated with, and management of, chemotherapy-induced diarrhoea is the foundation for optimum treatment of toxic effects. Adequate--and, if necessary, repeated--assessment, appropriate use of loperamide, and knowledge of fluid resuscitation requirements of affected patients is the second crucial step. Use of octreotide and seeking specialist advice early for patients who do not respond to treatment will reduce morbidity and mortality. In view of the burden of chemotherapy-induced diarrhoea, appropriate multidisciplinary research to assess meaningful endpoints is urgently required.

Is fecal microbiota transplantation (FMT) an effective treatment for patients with functional gastrointestinal disorders (FGID)?

BACKGROUND

Despite its high prevalence and significant effect on quality of life, the etiology of functional gastrointestinal disorders (FGID), and specifically irritable bowel syndrome (IBS), has yet to be fully elucidated. While alterations in immunity, motility, and the brain-gut axis have been implicated in disease pathogenesis, the intestinal microbiota are increasingly being shown to play a role and numerous studies have demonstrated significant differences from normal in the intestinal flora of patients with FGID, and between types of FGID. Fecal microbiota transplantation (FMT) is a curative therapy for Clostridium difficile infection (CDI), a disease hallmarked by intestinal dysbiosis, and FMT is now being explored as a means to also restore intestinal homeostasis in FGID.

PURPOSE

This review aims to investigate the role of intestinal microbiota in the pathogenesis of FGID, the implications of FMT for the treatment of FGID, and the challenges encountered in measuring response to a specific intervention in patients with FGID.

Psychobiotics and the gut-brain axis: in the pursuit of happiness

The human intestine houses an astounding number and species of microorganisms, estimated at more than 10(14) gut microbiota and composed of over a thousand species. An individual's profile of microbiota is continually influenced by a variety of factors including but not limited to genetics, age, sex, diet, and lifestyle. Although each person's microbial profile is distinct, the relative abundance and distribution of bacterial species is similar among healthy individuals, aiding in the maintenance of one's overall health. Consequently, the ability of gut microbiota to bidirectionally communicate with the brain, known as the gut-brain axis, in the modulation of human health is at the forefront of current research. At a basic level, the gut microbiota interacts with the human host in a mutualistic relationship - the host intestine provides the bacteria with an environment to grow and the bacterium aids in governing homeostasis within the host. Therefore, it is reasonable to think that the lack of healthy gut microbiota may also lead to a deterioration of these relationships and ultimately disease. Indeed, a dysfunction in the gut-brain axis has been elucidated by a multitude of studies linked to neuropsychological, metabolic, and gastrointestinal disorders. For instance, altered microbiota has been linked to neuropsychological disorders including depression and autism spectrum disorder, metabolic disorders such as obesity, and gastrointestinal disorders including inflammatory bowel disease and irritable bowel syndrome. Fortunately, studies have also indicated that gut microbiota may be modulated with the use of probiotics, antibiotics, and fecal microbiota transplants as a prospect for therapy in microbiota-associated diseases. This modulation of gut microbiota is currently a growing area of research as it just might hold the key to treatment.

The role of intestinal bacteria overgrowth in obesity-related nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease worldwide. It is a progressive disorder involving a spectrum of conditions that include pure steatosis without inflammation, nonalcoholic steatohepatitis (NASH), fibrosis and cirrhosis. The key factor in the pathophysiology of NAFLD is insulin resistance that determines lipid accumulation in the hepatocytes, which may be followed by lipid peroxidation, production of reactive oxygen species and consequent inflammation. Recent studies suggest that the characteristics of the gut microbiota are altered in NAFLD, and also, that small intestinal bacterial overgrowth (SIBO) contributes to the pathogenesis of this condition. This review presents the chief findings from all the controlled studies that evaluated SIBO, gut permeability and endotoxemia in human NAFLD. We also discuss the possible mechanisms involving SIBO, lipid accumulation and development of NASH. The understanding of these mechanisms may allow the development of new targets for NASH treatment in the future.

Breath testing for small intestinal bacterial overgrowth: maximizing test accuracy

The diagnosis of small intestinal bacterial overgrowth (SIBO) has increased considerably owing to a growing recognition of its association with common bowel symptoms including chronic diarrhea, bloating, abdominal distention, and the irritable bowel syndrome. Ideally, an accurate and objective diagnosis of SIBO should be established before initiating antibiotic treatment. Unfortunately, no perfect test exists for the diagnosis of SIBO. The current gold standard, small-bowel aspiration and quantitative culture, is limited by its high cost, invasive nature, lack of standardization, sampling error, and need for dedicated infrastructure. Although not without shortcomings, hydrogen breath testing provides the simplest noninvasive and widely available diagnostic modality for suspected SIBO. Carbohydrates such as lactulose and glucose are the most widely used substrates in hydrogen breath testing, with glucose arguably providing greater testing accuracy. Lactose, fructose, and sorbitol should not be used as substrates in the assessment of suspected SIBO. The measurement of methane in addition to hydrogen can increase the sensitivity of breath testing for SIBO. Diagnostic accuracy of hydrogen breath testing in SIBO can be maximized by careful patient selection for testing, proper test preparation, and standardization of test performance as well as test interpretation.

Pain management in patients with inflammatory bowel disease: translational approaches from bench to bedside

Abdominal pain is a common symptom in patients with inflammatory bowel disease (IBD) that negatively affects quality of life and can lead to increased health-seeking behavior. Although abdominal pain has been traditionally attributed to inflammation, there is growing literature demonstrating the existence of functional abdominal pain in patients with IBD, of which there are a variety of potential causes. Thus, when approaching a patient with IBD who has abdominal pain, in addition to IBD-related complications (e.g., inflammation/stricture), it is important to screen for related contributors, including peripheral factors (visceral hypersensitivity, bacterial overgrowth, and bowel dysmotility) and centrally mediated neurobiological and psychosocial underpinnings. These central factors include psychological symptoms/diagnoses, sleep disturbance, and stress. Opioid-induced hyperalgesia (e.g., narcotic bowel syndrome) is also growing in recognition as a potential central source of abdominal pain. This review draws from clinical studies and animal models of colitis and abdominal pain to consider how knowledge of these potential etiologies can be used to individualize treatment of abdominal pain in patients with IBD, including consideration of potential novel treatment modalities for the future. Accurate assessment of the source(s) of pain in patients with IBD can help guide appropriate diagnostic workup and use of disease-modifying therapy.

Gut microbiota in alcoholic liver disease: Pathogenetic role and therapeutic perspectives

Alcoholic liver disease (ALD) is the commonest cause of cirrhosis in many Western countries and it has a high rate of morbidity and mortality. The pathogenesis is characterized by complex interactions between metabolic intermediates of alcohol. Bacterial intestinal flora is itself responsible for production of endogenous ethanol through the fermentation of carbohydrates. The intestinal metabolism of alcohol produces a high concentration of toxic acetaldehyde that modifies gut permeability and microbiota equilibrium. Furthermore it causes direct hepatocyte damage. In patients who consume alcohol over a long period, there is a modification of gut microbiota and, in particular, an increment of Gram negative bacteria. This causes endotoxemia and hyperactivation of the immune system. Endotoxin is a constituent of Gram negative bacteria cell walls. Two types of receptors, cluster of differentiation 14 and Toll-like receptors-4, present on Kupffer cells, recognize endotoxins. Several studies have demonstrated the importance of gut-liver axis and new treatments have been studied in recent years to reduce progression of ALD modifying gut microbiota. It has focused attention on antibiotics, prebiotics, probiotics and synbiotics.

Intestinal microbiota: its role in digestive diseases

It is now well known that intestinal microbiota exerts not only several physiological functions, but has also been implied in the mechanisms of many conditions, both intestinal and extraintestinal. These advances, to the best of our knowledge, have been made possible by the development of new ways of studying gut flora. Metagenomics, the study of genetic material taken directly from environmental samples, avoiding individual culture, has become an excellent tool to study the human microbiota. Therefore, it has demonstrated an association between an altered intestinal microbiota and inflammatory bowel disease or irritable bowel syndrome, perhaps the most extensively studied conditions associated with this particular subject. However, microbiota has a potential role in the development of other diseases; their manifestations are not confined to the intestine only. In this article, an extensive updated review is conducted on the role intestinal microbiota has in health and in different diseases. Focus is made on the following conditions: inflammatory bowel disease, irritable bowel syndrome, celiac disease, hepatic encephalopathy, and obesity.

Small Intestinal Bacterial Overgrowth is Associated with Intestinal Inflammation in the Irritable Bowel Syndrome

Background and aim

Small intestinal bacterial overgrowth is encountered in bowel disorders, including irritable bowel symptoms. Low degrees of inflammation have been recently reported in the irritable bowel syndrome. We looked for the association between intestinal inflammation and small intestinal bacterial overgrowth in irritable bowel syndrome.

Methods

Small intestinal bacterial overgrowth was assessed by the H2 glucose breath test in 90 consecutive patients with irritable bowel syndrome. A check-up of the oral cavity was carried out before the breath testing. Further on, the patients were classified into two groups, positive and negative, at the breath test. Then they were tested for intestinal inflammation with a fecal test for calprotectin. We used a semiquantitative test for this study. Both groups were compared for the association of intestinal inflammation with small intestinal bacterial overgrowth.

Results

A number of 24/90 (26.7%) patients with irritable bowel syndrome had small intestinal bacterial overgrowth. A positive test for intestinal inflammation was significantly more frequent in patients with irritable bowel syndrome and small intestinal bacterial overgrowth (chi²: p<0.05).

Conclusions

Small intestinal bacterial overgrowth is present in almost one quarter of patients with irritable bowel syndrome. It is significantly associated with intestinal inflammation.

Gas and the microbiome

Humans are host to trillions of microbial colonizers that contribute significantly to human health and disease. Advances in sequencing and other technologies have facilitated dramatic advances in our knowledge of the types and number of organisms colonizing different areas of the body, and while our knowledge of the roles played by the different bacteria, fungi, and archaea has increased dramatically, there remains much to uncover. The microbes that colonize the human gut contribute to vitamin biosynthesis, immune modulation, and the breakdown of otherwise indigestible foods for nutrient harvest. Bacteria and archaea produce various gases as by-products of fermentation, and it is becoming increasingly understood that these gases have both direct and indirect effects on the gut, and may also be used as diagnostic markers, e.g., hydrogen production as measured by breath testing can be used to diagnose bacterial overgrowth. In this article, we review the roles and effects of hydrogen (H2), methane (CH4) and hydrogen sulfide (H2S) in the human gut.

A study of the methodological and clinical validity of the combined lactulose hydrogen breath test with scintigraphic oro-cecal transit test for diagnosing small intestinal bacterial overgrowth in IBS patients

BACKGROUND

Small intestinal bacterial overgrowth (SIBO) may be a cause of irritable bowel syndrome (IBS); however, current investigations have important limitations. We aimed to identify clinically relevant diagnostic criteria for SIBO based on lactulose hydrogen breath test (LHBT) alone and combined with scintigraphic measurement of oro-cecal transit (SOCT).

METHODS

Results of LHBT/SOCT investigation from 89 IBS patients and 13 healthy volunteers were included in a systematic analysis of six published criteria for SIBO diagnosis. Clinical relevance of competing criteria was determined by assessing (i) prevalence of SIBO in IBS patients and healthy volunteers (ii) if SIBO diagnosis predicted improvement in IBS symptoms in a prospective, pilot therapeutic trial of a non-absorbable antibiotic (rifaximin 600 mg b.d.) in IBS patients.

KEY RESULTS

Reproducibility of SIBO diagnosis by combined LHBT/SOCT was near perfect. A ≥5 ppm H2 increase prior to appearance of cecal contrast was detected in more IBS patients than healthy volunteers (35/89 vs 1/13; p = 0.026), but not for other diagnostic criteria. IBS patients with SIBO, compared to those without SIBO, reported significantly greater improvement in abdominal symptoms following rifaximin therapy (p < 0.002 overall IBS symptom severity). This improvement was most marked in D-IBS patients in whom all symptoms improved, including stool frequency and consistency (all p < 0.004).

CONCLUSIONS & INFERENCES

Combined LHBT/SOCT testing using a H2 5 ppm cutoff may identify a subgroup of IBS patients with SIBO. Pilot data examining the clinical response to rifaximin suggest that this subset of IBS patients may benefit more than those with a normal test.

The microbiota-gut-brain axis in functional gastrointestinal disorders

Functional gastrointestinal disorders (FGIDs) are highly prevalent and pose a significant burden on health care and society, and impact patients' quality of life. FGIDs comprise a heterogeneous group of disorders, with unclear underlying pathophysiology. They are considered to result from the interaction of altered gut physiology and psychological factors via the gut-brain axis, where brain and gut symptoms are reciprocally influencing each other's expression. Intestinal microbiota, as a part of the gut-brain axis, plays a central role in FGIDs. Patients with Irritable Bowel Syndrome, a prototype of FGIDs, display altered composition of the gut microbiota compared with healthy controls and benefit, at the gastrointestinal and psychological levels, from the use of probiotics and antibiotics. This review aims to recapitulate the available literature on FGIDs and microbiota-gut-brain axis.

Small intestinal bacterial overgrowth in Parkinson's disease

BACKGROUND

Recent studies reported a high prevalence of small intestinal bacterial overgrowth (SIBO) in Parkinson's disease (PD), and a possible association with gastrointestinal symptoms and worse motor function. We aimed to study the prevalence and the potential impact of SIBO on gastrointestinal symptoms, motor function, and quality of life in a large cohort of PD patients.

METHODS

103 Consecutive PD patients were assessed using the lactulose-hydrogen breath test; questionnaires of gastrointestinal symptoms and quality of life (PDQ-39); the Unified PD Rating Scale (UPDRS) including "on"-medication Part III (motor severity) score; and objective and quantitative measures of bradykinesia (Purdue Pegboard and timed test of gait). Patients and evaluating investigators were blind to SIBO status.

RESULTS

25.3% of PD patients were SIBO-positive. SIBO-positive patients had a shorter mean duration of PD (5.2 ± 4.1 vs. 8.1 ± 5.5 years, P = 0.007). After adjusting for disease duration, SIBO was significantly associated with lower constipation and tenesmus severity scores, but worse scores across a range of "on"-medication motor assessments (accounting for 4.2-9.0% of the variance in motor scores). There was no association between SIBO and motor fluctuations or PDQ-39 Summary Index scores.

CONCLUSIONS

This is the largest study to date on SIBO in PD. SIBO was detected in one quarter of patients, including patients recently diagnosed with the disease. SIBO was not associated with worse gastrointestinal symptoms, but independently predicted worse motor function. Properly designed treatment trials are needed to confirm a causal link between SIBO and worse motor function in PD.

A case of colonic pseudoobstruction related to bacterial overgrowth due to a sigmoidocecal fistula

Colocolic fistulas are usually a complication of an inflammatory or neoplastic process. Development of these abnormal bowel communications may lead to bacterial overgrowth. We report on a 71-year-old man with a one-year history of recurrent abdominal distension and irregular bowel habits. Abdominal X-rays and computed tomography showed multiple air-fluid levels and loops of distended bowel without evidence of mechanical obstruction or diverticulitis. Colonoscopy showed a fistulous tract between the sigmoid colon and cecum. Results of a lactulose breath test showed high fasting breath CH4 levels, which were thought to be the result of intestinal bacterial overgrowth. The patient was diagnosed with a colonic pseudo-obstruction associated with bacterial overgrowth due to a sigmoidocecal fistula. We recommended surgical correction of the sigmoidocecal fistula; however, the patient requested medical treatment. After antibiotic therapy, the patient still had mild symptoms but no acute exacerbations.

Review article: small intestinal bacterial overgrowth--prevalence, clinical features, current and developing diagnostic tests, and treatment

BACKGROUND

The symptoms and signs of small intestinal bacterial overgrowth (SIBO) are often identical to a variety of diseases and can lead to diagnostic confusion.

AIMS

To review the diagnostic options for SIBO and present new investigative options for the condition.

METHODS

A literature search was performed on MEDLINE, EMBASE and Web of Science for English articles and abstracts. Search terms included free text words and combinations of the following terms 'small intestinal bacterial overgrowth', 'small bowel bacterial overgrowth', 'diagnostic tests', 'treatment', 'antibiotics', 'probiotics', 'metabonomics', 'proton nuclear magnetic resonance spectroscopy', 'electronic nose' and 'field asymmetric ion mobility spectrometry'.

RESULTS

All of the available methods to test for SIBO have inherent limitations and no 'gold-standard' diagnostic test for the condition exists. Accurate diagnosis of SIBO requires identification of bacterial species growing inappropriately within the small intestine and symptom response to antibiotics. Proton nuclear magnetic resonance spectroscopy, electronic nose technology and/or field asymmetric ion mobility spectrometry may represent better investigative options for the condition.

CONCLUSIONS

Novel diagnostic options are needed to supplement or replace available tests.

Gastrointestinal bacterial overgrowth: pathogenesis and clinical significance

Small intestinal bacterial overgrowth (SIBO) is defined as the presence of an abnormally high number of coliform bacteria in the small bowel. It is associated with a broad range of predisposing small intestinal motility disorders and with surgical procedures that result in bowel stasis. The most common symptoms associated with SIBO include diarrhea, flatulence, abdominal pain and bloating. Quantitative culture of small bowel contents and a variety of indirect tests have been used over the years in an attempt to facilitate the diagnosis of SIBO. The indirect tests include breath tests and biochemical tests based on bacterial metabolism of a variety of substrates. Unfortunately, there is no single valid test for SIBO, and the accuracy of all current tests remains limited due to the failure of culture to be a gold standard and the lack of standardization of the normal bowel flora in the small intestine. Currently, the ideal approach to treat SIBO is to treat the underlying disease, eradicate overgrowth, and address nutritional deficiencies that may be associated with the development of SIBO.