Lactulose Breath Testing as a Predictor of Response to Rifaximin in Patients With Irritable Bowel Syndrome With Diarrhea

Common misconceptions and controversies in the management of irritable bowel syndrome

Despite an increase in our understanding of the pathophysiology of irritable bowel syndrome (IBS), in the context of abnormal gut-brain axis communication, and advances in both pharmacological and non-pharmacological treatment of the disorder, there remain areas in which there are misconceptions and controversies in the clinical management of IBS. This Perspective aims to highlight some of the most common misconceptions and controversies in IBS management, including those that the scientific literature has resolved, but for which further education of clinicians dealing with patients with IBS might be required to implement the findings from medical research. Areas of remaining contention are also discussed, as are suggestions as to how these issues could be addressed, both by advances in clinical practice and by further research.

Treatment of small intestinal bacterial overgrowth in Chilean patients with irritable bowel syndrome: A prospective and comparative study

INTRODUCTION AND AIM

Patients with disorders of the gut-brain axis, such as irritable bowel syndrome (IBS), often exhibit small intestinal bacterial overgrowth (SIBO). Its treatment includes rifaximin (RF), ciprofloxacin (CF), neomycin, sulfamethoxazole-trimethoprim, and metronidazole (MZ). RF is a non-absorbable antibiotic, postulated to have fewer adverse effects. Our aim was to assess symptomatic response and SIBO eradication in patients with IBS, using three antibiotic regimens.

METHODS

A prospective, randomized, double-blind study was conducted on IBS patients over 18 years of age, utilizing the Rome IV questionnaire and lactulose breath test. Those diagnosed with SIBO were randomly assigned to receive antibiotic treatment. Group A was treated with RF, group B with CF, and group C with MZ, each for 10 days. Treatment response was evaluated based on the SIBO eradication rate 15 days after completing therapy, utilizing hydrogen and methane breath tests with lactulose. Self-reported symptoms were recorded on a 10-point Likert scale before, during, and after treatment.

RESULTS

Ninety-seven patients with IBS and SIBO were included, 81% of whom completed treatment. Fifty-nine percent of the patients treated with RF achieved SIBO eradication, compared with 53% and 79% of those treated with CR and MZ, respectively. Metronidazole reduced more methane levels, compared with the other groups. However, the greatest reduction in abdominal pain and bloating was observed in the RF group, with a lower percentage of adverse events.

CONCLUSIONS

Patients with IBS and SIBO benefit from antibiotic therapy. MZ exhibited the best SIBO eradication rate, but RF demonstrated greater symptomatic improvement and a lower rate of adverse effects.

Effect, Tolerability, and Safety of Exclusive Palatable Elemental Diet in Patients with Intestinal Microbial Overgrowth

BACKGROUND & AIMS

Elemental diets (EDs) have desirable safety and efficacy profiles in several clinical settings partly because of modulation of gut microbiome. Palatability of EDs remains the main barrier to compliance/adherence, and their effect has not been prospectively explored in microbiome-driven disorders, such as small intestinal bacterial overgrowth (SIBO) and intestinal methanogen overgrowth (IMO). We aimed to assess the effect, tolerance, and safety of a novel palatable ED (PED) in subjects with IMO and/or SIBO.

METHODS

Adult subjects with positive lactulose breath tests for SIBO and/or IMO completed 1 week of screening, 2 weeks of exclusive oral PED, and 2 weeks of follow-up during reintroduction of regular diet. Primary end point was changes in stool microbiome after PED and reintroduction of regular diet. Secondary end points included tolerability, rate of normalization of lactulose breath tests, change in stool form based on daily diary and artificial intelligence-analyzed images, symptomatic response, and adverse events.

RESULTS

All 30 enrolled subjects tolerated the PED and completed the trial. Several taxonomic differences were detected including decreased relative abundance of Prevotella_9 and Fusobacterium. Abundance of Methanobrevibacter smithii decreased at the end of the trial and correlated with average daily methane levels (P = .024; r = 0.489). Maximum methane levels (41 ± 35 to 12 ± 15 ppm; P < .001) and hydrogen rise (43 ± 42 to 12 ± 11 ppm; P < .001) dropped significantly, with 73% normalizing their lactulose breath tests. Adequate global relief of symptoms was reported in 83% of subjects. No serious or severe adverse events were observed.

CONCLUSIONS

PED significantly impacts the gut microbiome. Tolerance to EDs improves with enhanced palatability. Larger studies with longer follow-up are needed to assess response durability. (ClinicalTrials.gov ID: NCT05978973).

Impact of Positive Glucose, Lactose, and Fructose Hydrogen Breath Tests on Symptoms and Quality of Life in Irritable Bowel Syndrome

BACKGROUND

Gas production due to fermentation from fructose malabsorption (FM) or lactose malabsorption (LM) and small intestinal bacterial overgrowth (SIBO) contribute to the development of gastrointestinal symptoms in patients with irritable bowel syndrome (IBS). However, the impact of the carbohydrate malabsorption, unlike SIBO, is relatively unknown.

METHODOLOGY

A multicenter, prospective study of consecutive adults with IBS who underwent a hydrogen breath test (HBT) (glucose, 75 g; lactose, 25 g; or fructose, 25 g) was conducted. The proportion of patients who tested positive for glucose, fructose and lactose HBT were evaluated. The symptom severity, psychology, and quality of life of subjects with SIBO were compared with those having LM and/or FM. Independent factors associated with severe IBS (IBS-symptom severity scale: IBS-SSS > 300) were explored.

RESULTS

A total of 116 subjects were included (median age 56 years, male 35.3%). Of these, 23.3% (27/116), 85.7% (24/28), and 44.4% (16/36) of them tested positive for glucose, lactose, and fructose HBT, respectively. Among those with a positive HBT (n = 65), patients with SIBO were more likely to have the diarrhea-predominant subtype of IBS (77.8% vs. 47.4%, p = 0.014). Severe IBS was associated with SIBO, compared with LM/FM (SIBO: 36.4% vs. LM: 9.1%/FM 13.3%, p = 0.016). With multivariate analysis, SIBO (OR 5.25, p = 0.028) and depression (OR 5.59, p = 0.030) were independently associated with severe IBS.

CONCLUSION

Although LM and FM commonly co-exist in IBS, their clinical relevance appears to be less significant than that of SIBO. The connection between SIBO with depression reinforces the importance of the microbiome-gut-brain axis in IBS.

Usefulness of a Digital Tool to Improve Methodology and Reporting of Breath Tests for Small Intestinal Bacterial Overgrowth

GOALS

We aimed to determine if the use of a web-based digital tool could improve methodology and reporting of breath tests (BT).

BACKGROUND

Although BT represent a noninvasive and low-cost tool for the diagnosis of small intestinal bacterial overgrowth (SIBO), lack of standardization and poor test performance have been described.

METHODS

We performed a retrospective analysis of a consecutive series of BT reports from 8 different gastroenterology units during the period April 2024 to July 2024. Data from the BT reports was extracted, masked, and uploaded in a digital tool that supports the entire breath test process and creates a report. Three experts in SIBO who were blinded for the test interpretation determined a diagnosis for each patient and delineated a total of 12 quality items that considered relevant to be included in a BT report. The main outcomes of the study were accuracy (ie, proportion of correct diagnoses) and quality of BT reports.

RESULTS

A total of 210 BT were analyzed; the type of substrate was informed in 187 (89.0%) BT and lactulose was used in most of the studies (162/187, 86.6%). Most tests measured only hydrogen (89.5%) and 38 (18.1%) extended the BT for <90 minutes. SIBO was diagnosed in 92 (43.8%) and 79 (37.6%) patients in the original BT report and the digital tool report, respectively. As compared with the diagnosis by the expert gastroenterologists and current guidelines, the original report was accurate in 182 (86.6%) patients and the digital tool report in 210 (100%) patients (P<0.0001). Regarding quality of reporting, the original BT report had a median of 5 (3 to 8) items included and the digital tool report described a median of 9 (7 to 11) items (P<0.0001).

CONCLUSIONS

Breath tests methodology and interpretation for the diagnosis of SIBO are heterogenous and do not comply with current guidelines. The use of a web-based digital tool specifically developed to assist the entire BT process appears to improve accuracy and quality of reports.

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.

Management of abdominal bloating and distension, from subjective to objective

Abdominal distension is a clinical occurrence that involves a measurable, objective increase in abdominal circumference, which patients report as feeling like pregnant or like having a balloon inside the abdomen. This sign is often preceded by a subjective feeling of abdominal heaviness or bloating, reported as the sensation of having a huge amount of gas trapped inside. These manifestations are highly prevalent and may reflect on their own a gut-brain axis condition, such as functional abdominal distension, or be part of other disorders such as functional dyspepsia or irritable bowel syndrome (IBS). The prevalence of abdominal distension and bloating is 3.5 %. However, when associated with other gut-brain axis disorders such as dyspepsia or IBS, prevalence grows above 50 %. The etiology and pathophysiology of abdominal bloating and distension are highly complex and represent a challenge for both the practitioner and the patient. The patient often associates these sensations with trapped gas, and attributes them to some food intolerance, hence he/she adopts a highly restrictive diet that fails to resolve distension while incurring the risk of nutritional deficiencies or secondary dysbiosis, making a directed treatment guideline necessary.

Low dose rifaximin combined with N-acetylcysteine is superior to rifaximin alone in a rat model of IBS-D: a randomized trial

Rifaximin is FDA-approved for treatment of irritable bowel syndrome with diarrhea (IBS-D), but poor solubility may limit its efficacy against microbes in the mucus layer, e.g. Escherichia coli. Here we evaluate adding the mucolytic N-acetylcysteine (NAC) to improve rifaximin efficacy. In a resazurin checkerboard assay, combining rifaximin with NAC had significant synergistic effects in reducing E. coli levels. The optimal rifaximin + NAC combination was then tested in a validated rat model of IBS-D (induced by cytolethal distending toxin [CdtB] inoculation). Rats were inoculated with vehicle and treated with placebo (Control-PBS) or rifaximin + NAC (Control-Rif + NAC, safety), or inoculated with CdtB and treated with placebo (CdtB-PBS), rifaximin (CdtB-Rifaximin), or rifaximin + NAC (CdtB-Rif + NAC) for 10 days. CdtB-inoculated rats (CdtB-PBS) developed wide variability in stool consistency (P = 0.0014) vs. controls (Control-PBS). Stool variability normalized in rats treated with rifaximin + NAC (CdtB-Rif + NAC) but not rifaximin alone (CdtB-Rifaximin). Small bowel bacterial levels were elevated in CdtB-PBS rats but normalized in CdtB-Rif + NAC but not CdtB-Rifaximin rats. E. coli and Desulfovibrio spp levels (each associated with different IBS-D microtypes) were also elevated in CdtB-inoculated (CdtB-PBS) but normalized in CdtB-Rif + NAC rats. Cytokine levels normalized only in CdtB-Rif + NAC rats, in a manner predicted to be associated with reduced diarrhea driven by reduced E. coli. These findings suggest that combining rifaximin with NAC may improve the percentage of IBS-D patients responding to treatment.

Critical appraisal of the SIBO hypothesis and breath testing: A clinical practice update endorsed by the European society of neurogastroenterology and motility (ESNM) and the American neurogastroenterology and motility society (ANMS)

BACKGROUND

There is compelling evidence that microbe-host interactions in the intestinal tract underlie many human disorders, including disorders of gut-brain interactions (previously termed functional bowel disorders), such as irritable bowel syndrome (IBS). Small intestinal bacterial overgrowth (SIBO) has been recognized for over a century in patients with predisposing conditions causing intestinal stasis, such as surgical alteration of the small bowel or chronic diseases, including scleroderma and is associated with diarrhea and signs of malabsorption. Over 20 years ago, it was hypothesized that increased numbers of small intestine bacteria might also account for symptoms in the absence of malabsorption in IBS and related disorders. This SIBO-IBS hypothesis stimulated significant research and helped focus the profession's attention on the importance of microbe-host interactions as a potential pathophysiological mechanism in IBS.

PURPOSE

However, after two decades, this hypothesis remains unproven. Moreover, it has led to serious unintended consequences, namely the widespread use of unreliable and unvalidated breath tests as a diagnostic test for SIBO and a resultant injudicious use of antibiotics. In this review, we examine why the SIBO hypothesis remains unproven and, given the unintended consequences, discuss why it is time to reject this hypothesis and its reliance on breath testing. We also examine recent IBS studies of bacterial communities in the GI tract, their composition and functions, and their interactions with the host. While these studies provide important insights to guide future research, they highlight the need for further mechanistic studies of microbe-host interactions in IBS patients before we can understand their possible role in diagnosis and treatment of patient with IBS and related disorders.

Bakterielle Fehlbesiedlung des Dünndarms

SIBO (Small Intestinal Bacterial Overgrowth) ist durch eine bakterielle Überwucherung oder Fehlbesiedlung des Dünndarms in Kombination mit intestinalen Symptomen definiert. Intestinale Stase, Hypochlorhydrie, Immundefizienz, Alter u.a. sind auslösende Faktoren. Die Therapie beinhaltet die Behandlung der auslösenden Grunderkrankung, den Ausgleich einer Mangelernährung, den Einsatz von Antibiotika und Probiotika sowie diätetische Maßnahmen.

Journal of Clinical Gastroenterology Lectureship Dubai 2022 : Management of Irritable Bowel Syndrome With Diarrhea

Irritable bowel syndrome (IBS) with diarrhea (IBS-D) affects ~1% of the general population and is characterized by abdominal pain associated with diarrhea. IBS-D symptoms significantly impact the quality of life of patients. Major uncertainties remain regarding the optimal management of these patients. Several therapies have been investigated over the years for the treatment of IBS-D. In the initial management, commonly prescribed approaches with an effect on global IBS symptoms include a low Fermentable Oligo-, Di-, Mono-Saccharides and Polyols diet and probiotics, while antispasmodics are used for targeting abdominal pain and loperamide for diarrhea only. Additional therapeutic options for the relief of global IBS symptoms include rifaximin, 5-HT 3 antagonists, gut-directed psychological therapies, and eluxadoline, while tricyclic antidepressants can target abdominal pain and bile acid sequestrants diarrhea. Promising evidence exists for the use of mesalazine and fecal microbiota transplantation in IBS-D, although further evidence is needed for definitive conclusions regarding their efficacy.

Symptomatic Response to Antibiotics in Patients With Small Intestinal Bacterial Overgrowth: A Systematic Review and Meta-analysis

Background/Aims

We performed a systematic review and meta-analysis evaluating the symptomatic response rate to antibiotics in patients with small intestinal bacterial overgrowth (SIBO). Similarly, we performed a meta-analysis on the symptomatic response to antibiotics in irritable bowel syndrome (IBS) patients with and without SIBO.

Methods

MEDLINE, EMBASE, Web of Science, and Cochrane databases were searched from inception to March 2021. Randomized controlled trials and prospective studies reporting dichotomous outcomes were included.

Results

There were 6 studies included in the first meta-analysis comparing the efficacy of antibiotics to placebo or no antibiotic. This included 196 patients, of whom 101 received antibiotics and 95 received placebo or no antibiotics. Significantly more patients improved with antibiotics (relative risk [95% CI] = 2.46 [1.33-4.55], P = 0.004). There were 4 studies included in the analysis comparing symptomatic response rates in IBS patients with or without SIBO with 266 IBS patients, of whom 172 had SIBO and 94 did not. The pooled response rate for symptomatic response was 51.2% in the SIBO group vs 23.4% in the no SIBO group, respectively. Significantly more IBS patients with SIBO responded to antibiotics compared to those without SIBO (relative risk [95% CI] = 2.07 [1.40-3.08], P = 0.0003).

Conclusions

Antibiotics appear to be efficacious in treating SIBO, although small sample sizes and poor data quality limit this interpretation. Symptomatic response rates also appear to be higher in IBS patients with SIBO. This may be the first example of precision medicine in IBS as opposed to our current empiric treatment approach. Large-multicenter studies are needed to verify the results.

Effects of a Nutraceutical Multicompound, with Probiotics, Hericium, PEA, and Undaria in Patients with Irritable Bowel Syndrome

Irritable bowel syndrome (IBS) is a functional gastrointestinal condition. Probiotics and other nutraceutical compounds can have specific indications in the context of IBS. A retrospective analysis was conducted on 123 IBS patients in order to evaluate the effects of an oral probiotic-based dietary supplement (Colicron, one cps/day for 4 wk) on stool consistency and pain intensity. Different time points were defined as follows: baseline (T0), 2 wk of treatment (T2), and 4 wk of treatment (T4). Stool consistency was assessed by using the Bristol Stool Scale. Pain intensity was evaluated by the Visual Analogue Scale (VAS). Patients who were initially categorized as normal retained regular bowel movements throughout the study. Both patients with constipation and diarrhea showed an improvement in the Bristol Stool Scale. The score increased from 1.5 ± 0.5 to 3.3 ± 0.7 (p < 0.001) and decreased from 6.5 ± 0.7 to 4.3 ± 0.9 (p < 0.001) at T4, respectively, compared to T0. The VAS score for pain in the pooled IBS patients improved from 6.7 ± 2.2 to 2.8 ± 1.9 at T0 vs T4 (p < 0.001), with a similar trend also observed when patients were categorized based on stool consistency: normal (from 5.2 ± 1.9 to 2.9 ± 1.7), constipation (from 7.5 ± 1.3 to 3.2 ± 2.2), and diarrhea (6.7 ± 2.3 to 2.5 ± 1.9) (p < 0.001).

Colicron could be useful in symptom relief, reducing abdominal pain and improving stool consistency of IBS patients. However, further controlled clinical trials are needed to confirm these preliminary findings.

The spectrum of gastrointestinal functional bowel disorders in joint hypermobility syndrome and in an academic referral center

Joint hypermobility syndrome (JHS) is a non-inflammatory hereditary disorder of connective tissue with varied clinical presentations, including frequent joint dislocations, hyperextensible skin, easy bruising, and abnormal paper-thin scar formation. Many of these patients have unexplained gastrointestinal (GI) symptoms. Our aim was to evaluate the prevalence of JHS in a tertiary gastroenterology motility clinic and the spectrum of functional bowel disorders in JHS patients. In this retrospective case series, we screened the medical records of 277 patients seen over 4 years at an academic GI Motility Center. The patients who met the criteria for JHS by Beighton hypermobility score were evaluated for the presence of functional GI disorders by Rome IV criteria. They also underwent gastric emptying study and glucose breath testing for small intestinal bacterial overgrowth. The prevalence of JHS in the study population was 9.7%. The mean age was 27 years, and 92.5% were female. The symptoms experienced by these patients include nausea/vomiting (89%), abdominal pain (70%), constipation (48%), and bloating (18.5%). The disorders associated with JHS include gastroparesis (52%), irritable bowel syndrome (55.5%), and gastroesophageal reflux disease (30%). Also, 10 patients (37%) were diagnosed with postural hypotension tachycardia syndrome secondary to autonomic dysfunction. Approximately 10% of patients with suspected functional bowel disorders have hypermobility syndrome. Hence, it is crucial to familiarize gastrointestinal practitioners with the criteria utilized to diagnose JHS and the methods to identify physical examination findings related to this condition.

Antibiotics and Probiotics for Irritable Bowel Syndrome

Irritable bowel syndrome (IBS) is a disorder of a gut-brain interaction characterised by abdominal pain and a change in stool form or frequency. Current symptom-based definitions and the classification of IBS promote heterogeneity amongst patients, meaning that there may be several different pathophysiological abnormalities leading to similar symptoms. Although our understanding of IBS is incomplete, there are several indicators that the microbiome may be involved in a subset of patients. Techniques including a faecal sample analysis, colonic biopsies, duodenal aspirates or surrogate markers, such as breath testing, have been used to examine the gut microbiota in individuals with IBS. Because of a lack of a clear definition of what constitutes a healthy gut microbiota, and the fact that alterations in gut microbiota have only been shown to be associated with IBS, a causal relationship is yet to be established. We discuss several hypotheses as to how dysbiosis may be responsible for IBS symptoms, as well as potential treatment strategies. We review the current evidence for the use of antibiotics and probiotics to alter the microbiome in an attempt to improve IBS symptoms. Rifaximin, a non-absorbable antibiotic, is the most studied antibiotic and has now been licensed for use in IBS with diarrhoea in the USA, but the drug remains unavailable in many countries for this indication. Current evidence also suggests that certain probiotics, including Lactobacillus plantarum DSM 9843 and Bifidobacterium bifidum MIMBb75, may be efficacious in some patients with IBS. Finally, we describe the future challenges facing us in our attempt to modulate the microbiome to treat IBS.

Understanding Our Tests: Hydrogen-Methane Breath Testing to Diagnose Small Intestinal Bacterial Overgrowth

There is increasing appreciation that small intestinal bacterial overgrowth (SIBO) drives many common gastrointestinal symptoms, including diarrhea, bloating, and abdominal pain. Breath testing via measurement of exhaled hydrogen and methane gases following ingestion of a readily metabolized carbohydrate has become an important noninvasive testing paradigm to help diagnose SIBO. However, because of a number of physiological and technical considerations, how and when to use breath testing in the diagnosis of SIBO remains a nuanced clinical decision. This narrative review provides a comprehensive overview of breath testing paradigms including the indications for testing, how to administer the test, and how patient factors influence breath testing results. We also explore the performance characteristics of breath testing (sensitivity, specificity, positive and negative predictive values, likelihood ratios, and diagnostic odds ratio). Additionally, we describe complementary and alternative tests for diagnosing SIBO. We discuss applications of breath testing for research. Current estimates of SIBO prevalence among commonly encountered high-risk populations are reviewed to provide pretest probability estimates under a variety of clinical situations. Finally, we discuss how to integrate breath test performance characteristics into clinical care decisions using clinical predictors and the Fagan nomogram.

Pros and Cons of Breath Testing for Small Intestinal Bacterial Overgrowth and Intestinal Methanogen Overgrowth

Breath testing is the most widely utilized modality to diagnose small intestinal bacterial overgrowth (SIBO) and/or intestinal methanogen overgrowth (IMO). Although SIBO can be diagnosed with small bowel aspiration and breath testing, IMO can only be diagnosed with breath testing in clinical practice. Breath testing can tailor antibiotic therapy and predict response to treatment; however, the test is limited by its indirect method of measurement and concerns about the variability of orocecal transit time. Like any clinical test, breath testing has inherent strengths and limitations, and results must be interpreted with consideration of the clinical context and influencing factors. Recent studies have demonstrated the expanding clinical utility of breath testing in the diagnosis, management, and prediction of treatment response in SIBO and particularly in IMO along with the identification of distinct breath test patterns such as flat-line and high baseline hydrogen. This article reviews the strengths and limitations of breath testing in diagnosing SIBO and IMO as well as its expanding utility in clinical practice.

Italian guidelines for the management of irritable bowel syndrome: Joint Consensus from the Italian Societies of: Gastroenterology and Endoscopy (SIGE), Neurogastroenterology and Motility (SINGEM), Hospital Gastroenterologists and Endoscopists (AIGO), Digestive Endoscopy (SIED), General Medicine (SIMG), Gastroenterology, Hepatology and Pediatric Nutrition (SIGENP) and Pediatrics (SIP)

The irritable bowel syndrome (IBS) is a chronic disorder of gut-brain interaction. IBS is still associated with areas of uncertainties, especially regarding the optimal diagnostic work-up and the more appropriate management. Experts from 7 Italian Societies conducted a Delphi consensus with literature summary and voting process on 27 statements. Recommendations and quality of evidence were evaluated using the grading of recommendations, assessment, development, and evaluation (GRADE) criteria. Consensus was defined as >80% agreement and reached for all statements. In terms of diagnosis, the consensus supports a positive diagnostic strategy with a symptom-based approach, including the psychological comorbidities assessment and the exclusion of alarm symptoms, together with the digital rectal examination, full blood count, C-reactive protein, serology for coeliac disease, and fecal calprotectin assessment. Colonoscopy should be recommended in patients with alarm features. Regarding treatment, the consensus strongly supports a dietary approach for patients with IBS, the use of soluble fiber, secretagogues, tricyclic antidepressants, psychologically directed therapies and, only in specific IBS subtypes, rifaximin. A conditional recommendation was achieved for probiotics, polyethylene glycol, antispasmodics, selective serotonin reuptake inhibitors and, only in specific IBS subtypes, 5-HT3 antagonists, 5-HT4 agonists, bile acid sequestrants.

Berberine and rifaximin effects on small intestinal bacterial overgrowth: Study protocol for an investigator-initiated, double-arm, open-label, randomized clinical trial (BRIEF-SIBO study)

Introduction: Small intestinal bacterial overgrowth (SIBO) leads to non-specific abdominal discomfort and nutrient malabsorption. Currently, rifaximin is widely applied in SIBO based on its antibacterial and non-absorbable nature. Berberine is a natural component of many popular medicine plants that ameliorates intestinal inflammation in humans through its modification of the gut microbiota. Potential effect of berberine to the gut may provide therapeutic target for SIBO. We aimed to evaluate the effect of berberine compared with rifaximin on SIBO patients. Methods: This is an investigator-initiated, single-center, open-label, double-arm randomized controlled trial, termed BRIEF-SIBO (Berberine and rifaximin effects for small intestinal bacterial overgrowth). In total, 180 patients will be recruited and allocated to an intervention group (berberine) and a control group (rifaximin). Each participant will receive one 400 mg drug twice a day (800 mg daily) for 2 weeks. The total follow-up period is 6 weeks from the start of medication. The primary outcome is a negative breath test. The secondary outcomes include abdominal symptom relief and alteration in gut microbiota. Efficacy assessment will be performed every 2 weeks, as well as safety assessment during the treatment. The primary hypothesis is that berberine is not inferior to rifaximin for SIBO. Discussion: The BRIEF-SIBO study is the first clinical trial assessing the eradication effects of 2 weeks of berberine treatment in SIBO patients. The effect of berberine will be fully verified by using rifaximin as the positive control. The findings of this study may have implications for the management of SIBO, especially increasing the awareness of both physicians and patients who are suffering from long-term abdominal discomfort and avoiding excessive examination.

Exhaled Hydrogen after Lactulose Hydrogen Breath Test in Patient with Duodenal Ulcer Disease-A Pilot Study for Helicobacter-pylori-Associated Gastroduodenal Disease

OBJECTIVES

The precipitating mechanism(s) from the inactive to the active stage of duodenal ulcer disease (DU) is unclear. It has been shown that hydrogen gas from colonic fermentation provides an important energy source for Helicobacter pylori (Hp) colonization. The lactulose hydrogen breath test (LHBT) is a useful tool to assess the small intestinal and/or colon fermentation. This study examines the association(s) between the status of gastroduodenal disease and the result of a lactulose hydrogen breath test (LHBT).

MATERIALS AND METHODS

We enrolled Hp-positive active duodenal ulcer (aDU) patients, inactive DU (iDU) patients and patients with a positive Hp infection without structural gastroduodenal lesion, i.e., simple gastritis (SG Hp+). The patients with simple gastritis without Hp infection (SG Hp-) served as controls. Histological examinations of the gastric mucosa and lactulose hydrogen breath test (LHBT) were performed.

RESULTS

SG Hp+ patients tend to have advanced gastritis (pangastritis or corpus-predominant gastritis) compared with SG Hp- patients (7/29 vs. 0/14, p = 0.08). More iDU patients had advanced gastritis than either the SG Hp+ (7/9 vs. 7/29, p = 0.006) or aDU patients (7/9 vs. 6/24, p = 0.013). In comparison with the aDU patients, the iDU patients were also older (52.1 ± 12.6 vs. 42.2 ± 11.9 years, p = 0.02) and had a lower mean area under the curve value of the LHBT(AUC) (209.1 ± 86.0 vs. 421.9 ± 70.9, p = 0.023).

CONCLUSION

aDU patients with a positive Hp infection have a lower grade of gastric mucosa damage than iDU patients and tend to have a higher level of exhaled hydrogen after LHBT.

Methanogens and Hydrogen Sulfide Producing Bacteria Guide Distinct Gut Microbe Profiles and Irritable Bowel Syndrome Subtypes

INTRODUCTION

Irritable bowel syndrome (IBS) includes diarrhea-predominant (IBS-D) and constipation-predominant (IBS-C) subtypes. We combined breath testing and stool microbiome sequencing to identify potential microbial drivers of IBS subtypes.

METHODS

IBS-C and IBS-D subjects from 2 randomized controlled trials (NCT03763175 and NCT04557215) were included. Baseline breath carbon dioxide, hydrogen (H 2 ), methane (CH 4 ), and hydrogen sulfide (H 2 S) levels were measured by gas chromatography, and baseline stool microbiome composition was analyzed by 16S rRNA sequencing. Microbial metabolic pathways were analyzed using Kyoto Encyclopedia of Genes and Genomes collection databases.

RESULTS

IBS-C subjects had higher breath CH 4 that correlated with higher gut microbial diversity and higher relative abundance (RA) of stool methanogens, predominantly Methanobrevibacter , as well as higher absolute abundance of Methanobrevibacter smithii in stool. IBS-D subjects had higher breath H 2 that correlated with lower microbial diversity and higher breath H 2 S that correlated with higher RA of H 2 S-producing bacteria, including Fusobacterium and Desulfovibrio spp. The predominant H 2 producers were different in these distinct microtypes, with higher RA of Ruminococcaceae and Christensenellaceae in IBS-C/CH 4 + (which correlated with Methanobacteriaceae RA) and higher Enterobacteriaceae RA in IBS-D. Finally, microbial metabolic pathway analysis revealed enrichment of Kyoto Encyclopedia of Genes and Genomes modules associated with methanogenesis and biosynthesis of methanogenesis cofactor F420 in IBS-C/CH 4 + subjects, whereas modules associated with H 2 S production, including sulfate reduction pathways, were enriched in IBS-D.

DISCUSSION

Our findings identify distinct gut microtypes linked to breath gas patterns in IBS-C and IBS-D subjects, driven by methanogens such as M. smithii and H 2 S producers such as Fusobacterium and Desulfovibrio spp, respectively.

Treatments targeting the luminal gut microbiota in patients with irritable bowel syndrome

Irritable bowel syndrome (IBS) is a common disorder of gut-brain interaction affecting 4% of the world's population. Patients with IBS experience chronic or recurrent abdominal pain in combination with altered bowel habits (diarrhea and/or constipation), and have reduced quality of life. Despite the high prevalence and substantial burden of IBS, its pathophysiology is incompletely understood and remains to be elucidated. The importance of the gut microenvironment has been highlighted in IBS, as there are signs that the gut microbiota of patients differs from healthy controls. Recent studies have aimed to alter the gut microbiota and thereby, attempted to alleviate gastrointestinal symptoms in IBS patients. We highlighted recent advances in common treatments that are targeting the luminal gut microbiota in IBS.

Modulating the gut microenvironment as a treatment strategy for irritable bowel syndrome: a narrative review

Irritable bowel syndrome (IBS) is a disorder of gut-brain interaction with a complex pathophysiology. Growing evidence suggests that alterations of the gut microenvironment, including microbiota composition and function, may be involved in symptom generation. Therefore, attempts to modulate the gut microenvironment have provided promising results as an indirect approach for IBS management. Antibiotics, probiotics, prebiotics, food and faecal microbiota transplantation are the main strategies for alleviating IBS symptom severity by modulating gut microbiota composition and function (eg. metabolism), gut barrier integrity and immune activity, although with varying efficacy. In this narrative review, we aim to provide an overview of the current approaches targeting the gut microenvironment in order to indirectly manage IBS symptoms.

Small Intestinal Bacterial Overgrowth In Various Functional Gastrointestinal Disorders: A Case-Control Study

INTRODUCTION

Small intestinal bacterial overgrowth (SIBO) is prevalent in irritable bowel syndrome (IBS), but its' association with other functional gastrointestinal disorders (FGIDs) is less certain. This study aimed to explore SIBO in a multi-racial Asian population with various FGIDs compared to non-FGID controls.

METHODOLOGY

Consecutive Asian adults with Rome III diagnosed common FGIDs (functional dyspepsia/FD, IBS and functional constipation/FC) and non-FGID controls were subjected to glucose breath testing, with hydrogen (H2) and methane (CH4) levels determined.

RESULTS

A total of 244 participants (FGIDs n = 186, controls n = 58, median age 45 years, males 36%, Malay ethnicity 76%) were recruited. FGIDs had a higher prevalence trend of SIBO compared to controls (16% FGIDs vs. 10% controls, p = 0.278) with 14% in FD, 18% in IBS and 17% in FC. Compared to controls, SIBO was associated with diarrhoea-predominant IBS (IBS-D) (24% vs. 10%, P = 0.050) but not with other types of FGIDs. IBS-D remained an independent predictor of SIBO (OR = 2.864, 95% CI 1.160-7.071, p = 0.023) but not PPI usage nor history of diabetes (both p > 0.050) at multivariate analysis. Compared to controls, SIBO in IBS-D was associated with an elevated H₂ level (≥ 20 ppm from baseline) (18% vs. 3%, p = 0.017), but not CH4 levels (≥ 10 ppm) (9% vs. 7%, p = 0.493). In addition, no difference was found in the prevalence of methane-positive SIBO between chronic constipation (constipation-predominant IBS and FC) compared to controls (9% vs. 7%, P = 0.466).

CONCLUSION

SIBO is prevalent amongst multi-ethnic Asian adults with and without FGIDs. Amongst various FGIDs, only IBS-D is significantly associated with SIBO.

Patients with breath test positive are necessary to be identified from irritable bowel syndrome: a clinical trial based on microbiomics and rifaximin sensitivity

BACKGROUND

As a non-invasive and effective diagnostic method for small intestinal bacterial overgrowth (SIBO), wild-use of breath test (BT) has demonstrated a high comorbidity rate in patients with diarrhea-predominant irritable bowel syndrome (IBS-D) and SIBO. Patients overlapping with SIBO respond better to rifaximin therapy than those with IBS-D only. Gut microbiota plays a critical role in both of these two diseases. We aimed to determine the microbial difference between IBS-D overlapping with/without SIBO, and to study the underlying mechanism of its sensitivity to rifaximin.

METHODS

Patients with IBS-D were categorized as BT-negative (IBSN) and BT-positive (IBSP). Healthy volunteers (BT-negative) were enrolled as healthy control. The patients were clinically evaluated before and after rifaximin treatment (0.4 g bid, 4 weeks). Blood, intestine, and stool samples were collected for cytokine assessment and gut microbial analyses.

RESULTS

Clinical complaints and microbial abundance were significantly higher in IBSP than in IBSN. In contrast, severe systemic inflammation and more active bacterial invasion function that were associated with enrichment of opportunistic pathogens were seen in IBSN. The symptoms of IBSP patients were relieved in different degrees after therapy, but the symptoms of IBSN rarely changed. We also found that the presence of IBSN-enriched genera ( Enterobacter and Enterococcus ) are unaffected by rifaximin therapy.

CONCLUSIONS

IBS-D patients overlapping with SIBO showed noticeably different fecal microbial composition and function compared with IBS-D only. The better response to rifaximin in those comorbid patients might associate with their different gut microbiota, which suggests that BT is necessary before IBS-D diagnosis and use of rifaximin.

REGISTRATION

Chinese Clinical Trial Registry, ChiCTR1800017911.

Functional bowel disorders with diarrhoea: Clinical guidelines of the United European Gastroenterology and European Society for Neurogastroenterology and Motility

Irritable bowel syndrome with diarrhoea (IBS-D) and functional diarrhoea (FDr) are the two major functional bowel disorders characterized by diarrhoea. In spite of their high prevalence, IBS-D and FDr are associated with major uncertainties, especially regarding their optimal diagnostic work-up and management. A Delphi consensus was performed with experts from 10 European countries who conducted a literature summary and voting process on 31 statements. Quality of evidence was evaluated using the grading of recommendations, assessment, development, and evaluation criteria. Consensus (defined as >80% agreement) was reached for all the statements. The panel agreed with the potential overlapping of IBS-D and FDr. In terms of diagnosis, the consensus supports a symptom-based approach also with the exclusion of alarm symptoms, recommending the evaluation of full blood count, C-reactive protein, serology for coeliac disease, and faecal calprotectin, and consideration of diagnosing bile acid diarrhoea. Colonoscopy with random biopsies in both the right and left colon is recommended in patients older than 50 years and in presence of alarm features. Regarding treatment, a strong consensus was achieved for the use of a diet low fermentable oligo-, di-, monosaccharides and polyols, gut-directed psychological therapies, rifaximin, loperamide, and eluxadoline. A weak or conditional recommendation was achieved for antispasmodics, probiotics, tryciclic antidepressants, bile acid sequestrants, 5-hydroxytryptamine-3 antagonists (i.e. alosetron, ondansetron, or ramosetron). A multinational group of European experts summarized the current state of consensus on the definition, diagnosis, and management of IBS-D and FDr.

Concomitant Irritable Bowel Syndrome Does Not Influence the Response to Antimicrobial Therapy in Patients with Functional Dyspepsia

BACKGROUND AND AIMS

Antimicrobial therapy improves symptoms in patients with irritable bowel syndrome (IBS), but the efficacy in functional dyspepsia (FD) is largely unknown. While FD and IBS frequently overlap, it is unknown if concomitant IBS in FD alters the response to antimicrobial therapy in FD. Thus, we aimed to assess and compare the effect of antimicrobial therapy on visceral sensory function and symptom improvement in FD patients with and without IBS.

METHODS

Adult patients with FD with or without IBS received rifaximin 550 mg BD for 10 days, followed by a 6-week follow-up period. The total gastrointestinal symptom score as measured by the SAGIS (Structured Assessment of Gastrointestinal Symptoms) questionnaire and subscores (dyspepsia, diarrhea, and constipation), symptom response to a standardized nutrient challenge and normalization of the glucose breath tests were measured.

RESULTS

Twenty-one consecutive adult patients with FD and 14/21 with concomitant IBS were recruited. Treatment with rifaximin resulted in a significant (p = 0.017) improvement in the total SAGIS score from 34.7 (± 15.4) at baseline to 26.0 (± 16.8) at 2 weeks and 25.6 (± 17.8) at 6 weeks post-treatment. Similarly, compared to baseline there was a statistically significant improvement in SAGIS subscores for dyspepsia and diarrhea (all p < 0.05) and effects persisted for 6 weeks post-treatment. Similarly, the symptom score (and subscores) following a standardized nutrient challenge improved significantly (p < 0.001) 2 weeks post-treatment. The presence of concomitant IBS did not significantly influence the improvement of symptoms after antibiotic therapy (all p > 0.5).

CONCLUSIONS

In FD patients, the response to antimicrobial therapy with rifaximin is not influenced by concomitant IBS symptoms.

Small intestinal bacterial overgrowth in patients with inflammatory bowel disease: A case-control study

BACKGROUND

Though small intestinal bacterial overgrowth (SIBO) is known in inflammatory bowel disease (IBD), the data on it are scanty and have limitations.

METHODS

Data on IBD patients undergoing glucose hydrogen breath test (GHBT) were retrospectively analyzed to evaluate the frequency and risk factors of SIBO in IBD compared to 66 healthy controls.

RESULTS

Patients with IBD (n=86; 45 ulcerative colitis [UC] and 41 Crohn's disease [CD]) more often had SIBO on GHBT than the healthy subjects (16/86 [18.6%] vs. 1/66 [1.5%]; p=0.002). SIBO was commoner among patients with CD than UC (14/41 [34.1%] vs. 2/45 [4.4%]; p=0.001). The frequency of SIBO among UC patients was comparable to healthy subjects (2/45 [4.4%] vs. 1/66 [1.5%]; p=not significant [NS]). Patients with CD than those with UC had higher values of maximum breath hydrogen and a greater area under the curve for breath hydrogen. Other factors associated with SIBO included female gender (11/16 [68.8%] with vs. 21/70 [30%] without SIBO; p=0.003), and having undergone surgery (8/16 [50%] vs. 6/70 [8.6%]; p=0.0002). SIBO patients had lower levels of total serum protein and albumin than those without SIBO (6.2 ± 1.5 g/dL vs. 7.0 ± 0.9 g/dL, respectively; p=0.009 and 3.5 ± 0.9 g/dL vs. 4.0 ± 0.6 g/dL, respectively; p=0.02). CD, female gender, and surgery for IBD tended to be the independent factors associated with SIBO among IBD patients on multivariate analysis.

CONCLUSIONS

Patients with IBD, particularly CD, female, and those having undergone surgery, have a higher risk of SIBO than the healthy controls.

Asian-Pacific consensus on small intestinal bacterial overgrowth in gastrointestinal disorders: An initiative of the Indian Neurogastroenterology and Motility Association

In the clinical setting, small intestinal bacterial overgrowth (SIBO) is a frequent, but under-diagnosed entity. SIBO is linked to various gastrointestinal (GI) and non-GI disorders with potentially significant morbidity. The optimal management of SIBO is undefined while there is a lack of published consensus guidelines. Against this background, under the auspices of the Indian Neurogastroenterology and Motility Association (INMA), formerly known as the Indian Motility and Functional Diseases Association (IMFDA), experts from the Asian-Pacific region with extensive research and clinical experience in the field of gut dysbiosis including SIBO developed this evidence-based practice guideline for the management of SIBO utilizing a modified Delphi process based upon 37 consensus statements, involving an electronic voting process as well as face-to-face meetings and review of relevant supporting literature. These statements include 6 statements on definition and epidemiology; 11 on etiopathogenesis and pathophysiology; 5 on clinical manifestations, differential diagnosis, and predictors; and 15 on investigations and treatment. When the proportion of those who voted either to accept completely or with minor reservations was 80% or higher, the statement was regarded as accepted. The members of the consensus team consider that this guideline would be valuable to inform clinical practice, teaching, and research on SIBO in the Asian-Pacific region as well as in other countries.

Review article: Diagnosis and investigation of irritable bowel syndrome

Irritable bowel syndrome (IBS) is a common disorder of gut-brain interaction. It is defined by the Rome criteria as the presence of abdominal pain, related to defaecation, associated with a change in stool form and/or frequency. The approach to diagnosis and investigation of suspected IBS varies between clinicians and, due in part to the uncertainty that can surround the diagnosis, many still consider it to be a diagnosis of exclusion. However, exhaustive investigation is both unnecessary and costly, and may also be counterproductive. Instead, physicians should aim to make a positive diagnosis, based on their clinical assessment of symptoms, and limit their use of investigations. The yield of routine blood tests in suspected IBS is low overall, but normal inflammatory markers may be reassuring. All patients should have serological testing for coeliac disease, irrespective of their predominant stool form. Routine testing of stool microbiology or faecal elastase is unnecessary; however, all patients with diarrhoea aged <45 should have a faecal calprotectin or a similar marker measured which, if positive, should lead to colonoscopy to exclude possible inflammatory bowel disease. Colonoscopy should also be undertaken in any patient reporting alarm symptoms suggestive of colorectal cancer, and in those whose presentation raises suspicion for microscopic colitis. Testing for bile acid diarrhoea should be considered for patients with IBS with diarrhoea where available. Hydrogen breath tests for lactose malabsorption or small intestinal bacterial overgrowth have no role in the routine assessment of suspected IBS. Adopting a standardised approach to the diagnosis and investigation of IBS will help to promote high-quality and high-value care for patients overall.

Review Article: Current and future treatment approaches for IBS with diarrhoea (IBS-D) and IBS mixed pattern (IBS-M)

BACKGROUND

Irritable bowel syndrome-diarrhoea (IBS-D) and IBS-mixed stool pattern (IBS-M) are disorders of gut-brain interaction characterised by abdominal pain associated with diarrhoea or both diarrhoea and constipation respectively. The pathophysiology of IBS-D/M is multifactorial and not completely understood; thus, treatment is aimed at multiple mechanisms such as altering gut microbiota, visceral hypersensitivity, intestinal permeability, gut-brain interaction and psychological strategies.

AIM

The goal of this article was to provide an up-to-date review of the current evidence for both non-pharmacological and pharmacological treatment options in IBS-D and IBS-M. Future treatments for IBS-D and IBS-M will also be discussed.

METHODS

Medline and Embase database searches (through April 30 2021) to identify clinical studies in subjects with IBS-D in which dietary modification, alternative treatments (probiotics, acupuncture, exercise) as well as FDA-approved medications were used.

RESULTS

Dietary modification is often the first line of therapy. Furthermore, lifestyle treatments include complementary alternative medications (CAM), probiotics and peppermint oil are useful adjuncts but have not specifically been described in IBS-D/M. Evidence strongly supports psychotherapy in the treatment of IBS. Beyond over-the counter anti-diarrhoeals, anti-spasmodics and anti-depressants, pharmacological treatment now includes treating for bile acid malabsorption and the FDA-approved medications rifaximin, eluxadoline and alosetron.

CONCLUSIONS

The treatment of IBS-D/M ideally involves a multidisciplinary approach of primary care, gastroenterologist and psychologist. Treatment often involves both non-pharmacological and pharmacological therapies. Future therapies may include faecal microbial transplant, Crofelemer and serotonin antagonists, but further studies are needed.

Gut microbiota dysbiosis in functional gastrointestinal disorders: Underpinning the symptoms and pathophysiology

Functional gastrointestinal disorders (FGIDs), currently known as disorders of gut-brain interaction, are emerging microbiota-gut-brain abnormalities that are prevalent worldwide. The pathogenesis of FGIDs is heterogeneous and is intertwined with gut microbiota and its derived molecule-modulated mechanisms, including gut dysmotility, visceral hypersensitivity, gut immune abnormalities, abnormal secretion, and impaired barrier function. There has been phenomenal progress in understanding the role of gut microbiota in FGIDs by underpinning the species alternations between healthy and pathological conditions such as FGIDs. However, the precise gut microbiota-directed cellular and molecular pathogeneses of FGIDs are yet enigmatic. Determining the mechanistic link between the gut microbiota and gastrointestinal (GI) diseases has been difficult due to (i) the lack of robust animal models imitating the various aspects of human FGID pathophysiology; (ii) the absence of longitudinal human and/or animal studies to unveil the interaction of the gut microbiota with FGID-relevant pathogenesis; (iii) uncertainty about connections between human and animal studies; and (iv) insufficient data supporting a holistic view of disease-specific pathophysiological changes in FGID patients. These unidentified gaps open possibilities to explore pathological mechanisms directed through gut microbiota dysbiosis in FGIDs. The current treatment options for dysbiotic gut microbiota are limited; dietary interventions, antibiotics, probiotics, and fecal microbiota transplantation are the front-line clinical options. Here, we review the contribution of gut microbiota and its derived molecules in gut homeostasis and explore the possible pathophysiological mechanisms involved in FGIDs leading to potential therapeutics options.

Emerging Role of the Gut Microbiome in Irritable Bowel Syndrome

Advances in bioinformatics have facilitated investigation of the role of gut microbiota in patients with irritable bowel syndrome (IBS). This article describes the evidence from epidemiologic and clinical observational studies highlighting the link between IBS and gut microbiome by investigating postinfection IBS, small intestinal bacterial overgrowth, and microbial dysbiosis. It highlights the effects of gut microbiota on mechanisms implicated in the pathophysiology of IBS, including gut-brain axis, visceral hypersensitivity, motility, epithelial barrier, and immune activation. In addition, it summarizes the current evidence on microbiome-guided therapies in IBS, including probiotics, antibiotics, diet, and fecal microbiota transplant.

Targeted pharmacotherapy of irritable bowel syndrome

PURPOSE OF REVIEW

Irritable bowel syndrome (IBS) is a highly prevalent functional gastrointestinal (GI) disorder with negative impact on quality of life and it represents a substantial economic burden on healthcare cost. The medical management of IBS is symptom directed. This review provides an update related to clinical trial data for novel treatment modalities in IBS targeting the gut epithelium secretagogue receptors and channels.

RECENT FINDINGS

The new Rome IV criteria define functional gastrointestinal disorders (FGID) as disorders of the gut-brain interaction. Pharmacological treatment modalities for IBS target gastrointestinal receptors and ion channels, peripheral opioid receptor, gut serotonin receptors, and the gut microbiome. New targeted pharmacotherapies have shown efficacy and safety in the treatment of patients with IBS.

SUMMARY

Diagnostic criteria for FGID, including IBS, have been revised in Rome IV and are defined as gut-brain disorders. Newly approved pharmacotherapy options with proven efficacy and acceptable side-effect profiles are available for the symptom-based management of IBS.

Pharmacological Therapies and Their Clinical Targets in Irritable Bowel Syndrome With Diarrhea

Irritable bowel syndrome (IBS) is one of the most common disorders of the gut-brain axis, which affects approximately 4% of the global population. The Rome IV criteria define IBS as chronic or recurrent abdominal pain associated with altered bowel habits. Patients can be categorized in four subtypes: IBS with predominant constipation (IBS-C), predominant diarrhea (IBS-D), mixed bowel habits (IBS-M), and unclassified (IBS-U). IBS is associated with a lower quality of life, reduced work productivity, and high healthcare costs. When comparing subtypes, patients with IBS-D report lower disease related quality of life. Due to the scope of this review, we have solely focused on patients with IBS-D. Choosing the right pharmacological treatment in these patients remains challenging due to the heterogeneous patient population, patients' expectation of the treatment outcome, unavailability of efficacious drugs, and the multifactorial and incompletely understood underlying pathophysiology. Currently, pharmacological treatment options target individual symptoms, such as abdominal pain, altered bowel habits, and bloating. In this review, we aimed to summarize the current and recent pharmacological treatment options in IBS-D, targeting the predominant gastrointestinal symptoms. Additionally, we proposed a pharmacological treatment algorithm which healthcare professionals could use when treating individual patients with IBS-D.

ACG Clinical Guideline: Management of Irritable Bowel Syndrome

Irritable bowel syndrome (IBS) is a highly prevalent, chronic disorder that significantly reduces patients' quality of life. Advances in diagnostic testing and in therapeutic options for patients with IBS led to the development of this first-ever American College of Gastroenterology clinical guideline for the management of IBS using Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) methodology. Twenty-five clinically important questions were assessed after a comprehensive literature search; 9 questions focused on diagnostic testing; 16 questions focused on therapeutic options. Consensus was obtained using a modified Delphi approach, and based on GRADE methodology, we endorse the following: We suggest that a positive diagnostic strategy as compared to a diagnostic strategy of exclusion be used to improve time to initiating appropriate therapy. We suggest that serologic testing be performed to rule out celiac disease in patients with IBS and diarrhea symptoms. We suggest that fecal calprotectin be checked in patients with suspected IBS and diarrhea symptoms to rule out inflammatory bowel disease. We recommend a limited trial of a low fermentable oligosaccharides, disacchardies, monosaccharides, polyols (FODMAP) diet in patients with IBS to improve global symptoms. We recommend the use of chloride channel activators and guanylate cyclase activators to treat global IBS with constipation symptoms. We recommend the use of rifaximin to treat global IBS with diarrhea symptoms. We suggest that gut-directed psychotherapy be used to treat global IBS symptoms. Additional statements and information regarding diagnostic strategies, specific drugs, doses, and duration of therapy can be found in the guideline.

AGA Clinical Practice Update on Small Intestinal Bacterial Overgrowth: Expert Review

DESCRIPTION

Thanks to ready access to hydrogen breath testing, small intestinal bacterial overgrowth (SIBO) is now commonly diagnosed among individuals presenting with a variety of gastrointestinal and even nongastrointestinal symptoms and is increasingly implicated in lay press and media in the causation of a diverse array of disorders. Its definition, however, remains controversial and true prevalence, accordingly, undefined. The purpose of this review, therefore, was to provide a historical background to the concept of SIBO, critically review current concepts of SIBO (including symptomatology, pathophysiology, clinical consequences, diagnosis and treatment), define unanswered questions and provide a road map toward their resolution.

METHODS

Best Practice Advice statements were developed following discussion by the 3 authors. Two authors each developed text around certain Best Practice Advice based on a review of available literature. All 3 authors reviewed the complete draft and after discussion, redrafting, and further review and revision, all of the authors agreed on a final draft. BEST PRACTICE ADVICE 1: The definition of SIBO as a clinical entity lacks precision and consistency; it is a term generally applied to a clinical disorder where symptoms, clinical signs, and/or laboratory abnormalities are attributed to changes in the numbers of bacteria or in the composition of the bacterial population in the small intestine. BEST PRACTICE ADVICE 2: Symptoms traditionally linked to SIBO include bloating, diarrhea, and abdominal pain/discomfort. Steatorrhea may be seen in more severe cases. BEST PRACTICE ADVICE 3: There is insufficient evidence to support the use of inflammatory markers, such as fecal calprotectin to detect SIBO. BEST PRACTICE ADVICE 4: Laboratory findings can include elevated folate and, less commonly, vitamin B-12 deficiency, or other nutritional deficiencies. BEST PRACTICE ADVICE 5: A major impediment to our ability to accurately define SIBO is our limited understanding of normal small intestinal microbial populations-progress in sampling technology and techniques to enumerate bacterial populations and their metabolic products should provide much needed clarity. BEST PRACTICE ADVICE 6: Controversy remains concerning the role of SIBO in the pathogenesis of common functional symptoms, such as those regarded as components of irritable bowel syndrome. BEST PRACTICE ADVICE 7: Management should focus on the identification and correction (where possible) of underlying causes, correction of nutritional deficiencies, and the administration of antibiotics. This is especially important for patients with significant maldigestion and malabsorption. BEST PRACTICE ADVICE 8: Although irritable bowel syndrome has been shown to respond to therapy with a poorly absorbed antibiotic, the role of SIBO or its eradication in the genesis of this response warrants further confirmation in randomized controlled trials. BEST PRACTICE ADVICE 9: There is a limited database to guide the clinician in developing antibiotic strategies for SIBO, in any context. Therapy remains, for the most part, empiric but must be ever mindful of the potential risks of long-term broad-spectrum antibiotic therapy.

Recent advances in diagnosis and management of irritable bowel syndrome

PURPOSE OF REVIEW

This review summarizes recent progress in the diagnosis and management of irritable bowel syndrome, with a focus on dietary and microbiota aspects.

RECENT FINDINGS

From a pathophysiological point of view, IBS is a multifactorial condition with both peripheral (transit) as central (visceral hypersensitivity, anxiety, depression) contribution in a cumulative fashion to the symptom pattern and severity. More recently, the focus has shifted to diet and microbiota. The number of dietary options that can be used for IBS and the understanding of determinants of their efficacy is rapidly increasing. Several studies have confirmed the efficacy of the low fermentable oligosaccharides, disaccharides, monosaccharides and polyols (FODMAP) diet. Sucrose-isomaltase deficiency has emerged as pathogenetic mechanisms in a subset of patients, who do not respond to low FODMAP diet but may respond to starch and sucrose elimination. Herbal remedies, probiotics and secretagogues have been the topic of additional treatment trials. The efficacy of fecal microbiota transplantation in IBS is variable across studies, but donor selection is emerging as a critical factor.

SUMMARY

Irritable bowel syndrome has evolved into a disorder of interaction between dietary factors and gut microbiota, with impact on bowel symptoms as well as extra-intestinal, central, symptoms. Dietary adjustments and treatments targeting the gut microbiota are areas of active research and clinical progress.

Marshall and Warren Lecture 2019: A paradigm shift in pathophysiological basis of irritable bowel syndrome and its implication on treatment

Irritable bowel syndrome (IBS), a common functional gastrointestinal disorder (FGID), has often been considered rather inappropriately as psychogenic in the past. Though psychological issues are important comorbidities in a proportion of IBS patients, the evidences are far from enough to label this condition as psychogenic only. In the recent past, evidences are emerging that underscores the concept supporting pure psychogenic theory of IBS and suggest this disorder to be rather microorganic. Accordingly, a move of Rome IV Committee attempting to delete the term "functional" and designating these to be disorders of "gut-brain interaction" rather than that of "brain-gut interaction," it emphasizes the importance of the gut over the brain in the pathogenesis. The introduction of the concept of multidimensional clinical profile in Rome IV requires attention to diagnostic category of FGID, overlap, severity, psychological issues, and physiological dysfunction or biomarkers; this attempts to recognize clinical variability and multidimensionality of pathophysiology and management of these disorders. The recognition of the biological factors in the pathogenesis of IBS is a significant paradigm shift in the recent time. This is somewhat similar to the progress in the pathogenesis of peptic ulcer disease from psychological factor to acid to Helicobacter pylori infection. It is expected that in the near future, therapeutic modalities targeting the different pathogenic mechanisms of different subtypes of IBS may bring revolution in management of the disorder.

Small Intestinal Bacterial Overgrowth and Irritable Bowel Syndrome - An Update

Small intestinal bacterial overgrowth (SIBO) is one manifestation of gut microbiome dysbiosis and is highly prevalent in IBS (Irritable Bowel Syndrome). SIBO can be diagnosed either by a small bowel aspirate culture showing ≥10³ colony-forming units (CFU) per mL of aspirate, or a positive hydrogen lactulose or glucose breath test. Numerous pathogenic organisms have been shown to be increased in subjects with SIBO and IBS, including but not limited to Enterococcus, Escherichia coli, and Klebsiella. In addition, Methanobrevibacter smithii, the causal organism in a positive methane breath test, has been linked to constipation predominant irritable bowel syndrome (IBS-C). As M. smithii is an archaeon and can overgrow in areas outside of the small intestine, it was recently proposed that the term intestinal methanogen overgrowth (IMO) is more appropriate for the overgrowth of these organisms. Due to gut microbiome dysbiosis, patients with IBS may have increased intestinal permeability, dysmotility, chronic inflammation, autoimmunity, decreased absorption of bile salts, and even altered enteral and central neuronal activity. As a consequence, SIBO and IBS share a myriad of symptoms including abdominal pain, distention, diarrhea, and bloating. Furthermore, gut microbiome dysbiosis may be associated with select neuropsychological symptoms, although more research is needed to confirm this connection. This review will focus on the role of the gut microbiome and SIBO in IBS, as well as novel innovations that may help better characterize intestinal overgrowth and microbial dysbiosis.