Modulation of the gut microbiota composition by rifaximin in non-constipated irritable bowel syndrome patients: a molecular approach

Gut microbiota in Alzheimer's disease: Understanding molecular pathways and potential therapeutic perspectives

Accumulating evidence suggests that gut microbiota (GM) plays a crucial role in Alzheimer's disease (AD) pathogenesis and progression. This narrative review explores the complex interplay between GM, the immune system, and the central nervous system in AD. We discuss mechanisms through which GM dysbiosis can compromise intestinal barrier integrity, enabling pro-inflammatory molecules and metabolites to enter systemic circulation and the brain, potentially contributing to AD hallmarks. Additionally, we examine other pathophysiological mechanisms by which GM may influence AD risk, including the production of short-chain fatty acids, secondary bile acids, and tryptophan metabolites. The role of the vagus nerve in gut-brain communication is also addressed. We highlight potential therapeutic implications of targeting GM in AD, focusing on antibiotics, probiotics, prebiotics, postbiotics, phytochemicals, and fecal microbiota transplantation. While preclinical studies showed promise, clinical evidence remains limited and inconsistent. We critically assess clinical trials, emphasizing challenges in translating GM-based therapies to AD patients. The reviewed evidence underscores the need for further research to elucidate precise molecular mechanisms linking GM to AD and determine whether GM dysbiosis is a contributing factor or consequence of AD pathology. Future studies should focus on large-scale clinical trials to validate GM-based interventions' efficacy and safety in AD.

Pharmacologic treatment of irritable bowel syndrome. Position statement of the Asociación Mexicana de Gastroenterología, 2024

INTRODUCTION

The aim of this position statement is to provide health professionals with an updated and evidence-based guideline for the pharmacologic management of irritable bowel syndrome (IBS) in Mexico.

MATERIAL AND METHODS

A literature review was conducted that included relevant guidelines and studies, up to the date of its publication. The mechanism of action, specific indications in IBS, safety profile, and availability of each therapeutic class were evaluated. The recommendations were developed by 14 experts, considering the clinical reality of IBS patients in Mexico.

RESULTS

Specific recommendations were issued for each class. Antispasmodics (alone or combined) are used as first-line therapy for pain management, whereas antidiarrheals, such as loperamide, are used for reducing diarrhea in diarrhea-predominant IBS (IBS-D) and laxatives are used for constipation in constipation-predominant IBS (IBS-C). 5-HT4 agonists (prucalopride and mosapride) are recommended in IBS-C and 5-HT3 antagonists (ondansetron) are recommended in IBS-D. Linaclotide is the only secretagogue available in Mexico and is used in IBS-C. Rifaximin-alpha stands out for its efficacy in a subgroup of patients with IBS-D or mixed IBS. Probiotics are conditionally recommended as adjuvant therapy due to heterogeneous evidence. Neuromodulators (tricyclic antidepressants, selective serotonin reuptake inhibitors, etc.) are recommended as second-line treatment for pain management. Mesalazine can be used in IBS-D, but the corresponding evidence is weak.

CONCLUSION

Overall, these recommendations provide a solid framework for personalizing treatment, based on the clinical characteristics of the Mexican patient with IBS.

"Pleiotropic" Effects of Antibiotics: New Modulators in Human Diseases

Antibiotics, widely used medications that have significantly increased life expectancy, possess a broad range of effects beyond their primary antibacterial activity. While some are recognized as adverse events, others have demonstrated unexpected benefits. These adjunctive effects, which have been defined as "pleiotropic" in the case of other pharmacological classes, include immunomodulatory properties and the modulation of the microbiota. Specifically, macrolides, tetracyclines, and fluoroquinolones have been shown to modulate the immune system in both acute and chronic conditions, including autoimmune disorders (e.g., rheumatoid arthritis, spondyloarthritis) and chronic inflammatory pulmonary diseases (e.g., asthma, chronic obstructive pulmonary disease). Azithromycin, in particular, is recommended for the long-term treatment of chronic inflammatory pulmonary diseases due to its well-established immunomodulatory effects. Furthermore, antibiotics influence the human microbiota. Rifaximin, for example, exerts a eubiotic effect that enhances the balance between the gut microbiota and the host immune cells and epithelial cells. These pleiotropic effects offer new therapeutic opportunities by interacting with human cells, signaling molecules, and bacteria involved in non-infectious diseases like spondyloarthritis and inflammatory bowel diseases. The aim of this review is to explore the pleiotropic potential of antibiotics, from molecular and cellular evidence to their clinical application, in order to optimize their use. Understanding these effects is essential to ensure careful use, particularly in consideration of the threat of antimicrobial resistance.

Validation of a Hand-Held Point-of-Care Device to Measure Breath Hydrogen and Its Utility in Detecting Response to Antibiotic Treatment

BACKGROUND

Breath testing for small intestinal bacterial overgrowth (SIBO) is typically performed using clinic-based equipment or single-use test kits.

AIMS

This study aimed to evaluate the utility of a portable, point-of-care breath analysis device (AIRE®, FoodMarble) in patients suspected to have SIBO. A technical assessment including a comparison to existing mail-in kits was first performed. Then, postprandial breath hydrogen levels of patients before and after antibiotic treatment were gathered and compared to levels seen in a healthy cohort.

METHODS

For the comparison, 50 patients suspected of having SIBO were provided with an AIRE device and performed concurrent LHBTs at-home with a mail-in breath test kit. For the postprandial analysis, twenty-four patients with chronic GI symptoms measured their postprandial hydrogen for 7 days prior to antibiotic treatment and for 7 days after treatment. 10 healthy controls also measured their postprandial hydrogen for 7 days.

RESULTS

Substantial agreement was demonstrated between AIRE and the mail-in kits for the performance of lactulose hydrogen breath tests (κ = 0.8). Prior to treatment, patients had significantly greater daily postprandial hydrogen than healthy controls (p < 0.001). The mean postprandial hydrogen of patients reduced significantly after treatment (p < 0.001).

CONCLUSIONS

Measuring postprandial hydrogen shows potential as a means of differentiating patients with chronic GI symptoms from healthy controls and may be useful in monitoring patients before, during, and after treatment. Future studies could help determine if pre-treatment breath gas levels are predictive of response to antibiotic treatment.

Cross-Cohort Gut Microbiome Signatures of Irritable Bowel Syndrome Presentation and Treatment

Irritable bowel syndrome (IBS) is a prevalent disorder of gut-brain interaction without a reliable cure. Evidence suggests that an alteration of the gut microbiome may contribute to IBS pathogenesis, motivating the development of microbiome-targeted therapies to alleviate IBS symptoms. However, IBS-specific microbiome signatures are variable across cohorts. A total of 9204 datasets were meta-analyzed, derived from fourteen IBS microbiome discovery cohorts, three validation cohorts for diet-microbiome interactions, and five rifaximin therapy cohorts. The consistent bacterial species and functional signatures associated with IBS were identified. Network analysis revealed two distinct IBS-enriched microbiota clusters; obligate anaerobes that are found commonly in the gut, and facultative anaerobes typically present in the mouth, implying a possible association between oral bacterial translocation to gut and IBS pathogenesis. By analyzing diet-microbiome interactions, microbiota-targeted diets that can potentially modulate the altered gut microbiota of IBS subjects toward a healthy status were identified. Furthermore, rifaximin treatment of IBS subjects was linked with a reduction in the abundance of facultatively anaerobic pathobionts. Gut microbiome signatures were identified across IBS cohorts that may inform the development of therapies for microbiome modulation in IBS. The microbiota-targeted diet patterns described may enable nutritional intervention trials in IBS and for assisting dietary management.

Rifaximin Alfa and Liver Diseases: More Than a Treatment for Encephalopathy, a Disease Modifier

RFX, a rifamycin-based antibacterial agent obtained by the culture of the actinomycete Streptomyces mediterranei, has a broad antibacterial spectrum covering gram- positive, gram-negative, aerobic, and anaerobic bacteria. RFX is an antibiotic that elicits its effect by inhibiting bacterial RNA synthesis. When administered orally, its intestinal absorption is extremely low (<0.4%), restricting antibacterial activity mainly in the intestinal tract, with few systemic side effects. RFX has been recommended by the American Association for the Study of Liver Diseases and the European Association for the Study of the Liver guidelines for the treatment of HE. RFX may contribute to restore hepatic function and to decrease the development of liver fibrosis. Its efficacy has been shown in patients with previous hepatic encephalopathy and several complications, such as infections, including spontaneous bacterial peritonitis, ascites and oesophageal variceal bleeding. Thus, RFX has an outstanding role in the therapeutic arsenal in hepatic cirrhosis, under the concept of disease modifier.

Sarcopenia in cirrhosis: Prospects for therapy targeted to gut microbiota

Decreased muscle mass and function, also known as sarcopenia, is common in patients with cirrhosis and is associated with a poor prognosis. Although the pathogenesis of this disorder has not been fully elucidated, a disordered gut-muscle axis probably plays an important role. Decreased barrier function of the gut and liver, gut dysbiosis, and small intestinal bacterial overgrowth (SIBO) can lead to increased blood levels of ammonia, lipopolysaccharides, pro-inflammatory mediators, and myostatin. These factors have complex negative effects on muscle mass and function. Drug interventions that target the gut microbiota (long-term use of rifaximin, lactulose, lactitol, or probiotics) positively affect most links of the compromised gut-muscle axis in patients with cirrhosis by decreasing the levels of hyperammonemia, bacterial translocation, and systemic inflammation and correcting gut dysbiosis and SIBO. However, although these drugs are promising, they have not yet been investigated in randomized controlled trials specifically for the treatment and prevention of sarcopenia in patients with cirrhosis. No data exist on the effects of fecal transplantation on most links of gut-muscle axis in cirrhosis; however, the results of animal experimental studies are promising.

Key determinants of success in fecal microbiota transplantation: From microbiome to clinic

Fecal microbiota transplantation (FMT) has achieved satisfactory results in preventing the recurrence of Clostridioides difficile infection, but these positive outcomes have only been partially replicated in other diseases. Several factors influence FMT success, including those related to donors and recipients (including diversity and specific composition of the gut microbiome, immune system, and host genetics) as well as to working protocols (fecal amount and number of infusions, route of delivery, and adjuvant treatments). Moreover, initial evidence suggests that the clinical success of FMT may be related to the degree of donor microbial engraftment. The application of cutting-edge technologies for microbiome assessment, along with changes in the current vision of fecal transplants, are expected to improve FMT protocols and outcomes. Here, we review the key determinants of FMT success and insights and strategies that will enable a close integration of lab-based and clinical approaches for increasing FMT success.

Eubiotic effect of rifaximin is associated with decreasing abdominal pain in symptomatic uncomplicated diverticular disease: results from an observational cohort study

BACKGROUND

Rifaximin effectively treats symptomatic uncomplicated diverticular disease (SUDD) and has shown eubiotic potential (i.e., an increase in resident microbial elements with potential beneficial effects) in other diseases. This study investigated changes in the fecal microbiome of patients with SUDD after repeated monthly treatment with rifaximin and the association of these changes with the severity of abdominal pain.

METHODS

This was a single-center, prospective, observational, uncontrolled cohort study. Patients received rifaximin 400 mg twice a day for 7 days per month for 6 months. Abdominal pain (assessed on a 4-point scale from 0 [no pain] to 3 [severe pain]) and fecal microbiome (assessed using 16 S rRNA gene sequencing) were assessed at inclusion (baseline) and 3 and 6 months. The Spearman's rank test analyzed the relationship between changes in the gut microbiome and the severity of abdominal pain. A p-value ≤ 0.05 was considered statistically significant.

RESULTS

Of the 23 patients enrolled, 12 patients completed the study and were included in the analysis. Baseline abdominal pain levels decreased significantly after 3 (p = 0.036) and 6 (p = 0.008) months of treatment with rifaximin. The abundance of Akkermansia in the fecal microbiome was significantly higher at 3 (p = 0.017) and 6 (p = 0.015) months versus baseline. The abundance of Ruminococcaceae (p = 0.034), Veillonellaceae (p = 0.028), and Dialister (p = 0.036) were significantly increased at 6 months versus baseline, whereas Anaerostipes (p = 0.049) was significantly decreased. The severity of abdominal pain was negatively correlated with the abundance of Akkermansia (r=-0.482; p = 0.003) and Ruminococcaceae (r=-0.371; p = 0.026) but not with Veillonellaceae, Dialister, or Anaerostipes. After 3 months of rifaximin, abdominal pain was significantly less in patients with Akkermansia in their fecal microbiome than in patients without Akkermansia (p = 0.022).

CONCLUSION

The eubiotic effect of rifaximin was associated with decreased abdominal pain in patients with SUDD.

Current and Future Therapeutic Options for Irritable Bowel Syndrome with Diarrhea and Functional Diarrhea

Irritable bowel syndrome with diarrhea and functional diarrhea are disorders of gut-brain interaction presenting with chronic diarrhea; they have significant impact on quality of life. The two conditions may exist as a continuum and their treatment may overlap. Response to first-line therapy with antispasmodics and anti-diarrheal agents is variable, leaving several patients with suboptimal symptom control and need for alternative therapeutic options. Our aim was to discuss current pharmacologic options and explore alternative therapeutic approaches and future perspectives for symptom management in irritable bowel syndrome with diarrhea and functional diarrhea. We conducted a search of PubMed, Cochrane, clinicaltrial.gov, major meeting abstracts for publications on current, alternative, and emerging drugs for irritable bowel syndrome with diarrhea and functional diarrhea. Currently approved therapeutic options for patients with first-line refractory irritable bowel syndrome with diarrhea and functional diarrhea include serotonin-3 receptor antagonists, eluxadoline and rifaximin. Despite their proven efficacy, cost and availability worldwide impact their utilization. One-third of patients with disorders of gut-brain interaction with diarrhea have bile acid diarrhea and may benefit from drugs targeting bile acid synthesis and excretion. Further understanding of underlying pathophysiology of irritable bowel syndrome with diarrhea and functional diarrhea related to bile acid metabolism, gastrointestinal transit, and microbiome has led to evaluation of novel therapeutic approaches, including fecal microbiota transplantation and enterobacterial "crapsules". These opportunities to treat disorders of gut-brain interaction with diarrhea should be followed with formal studies utilizing large samples of well-characterized patients at baseline and validated response outcomes as endpoints for regulatory approval.

Variability of strain engraftment and predictability of microbiome composition after fecal microbiota transplantation across different diseases

Fecal microbiota transplantation (FMT) is highly effective against recurrent Clostridioides difficile infection and is considered a promising treatment for other microbiome-related disorders, but a comprehensive understanding of microbial engraftment dynamics is lacking, which prevents informed applications of this therapeutic approach. Here, we performed an integrated shotgun metagenomic systematic meta-analysis of new and publicly available stool microbiomes collected from 226 triads of donors, pre-FMT recipients and post-FMT recipients across eight different disease types. By leveraging improved metagenomic strain-profiling to infer strain sharing, we found that recipients with higher donor strain engraftment were more likely to experience clinical success after FMT (P = 0.017) when evaluated across studies. Considering all cohorts, increased engraftment was noted in individuals receiving FMT from multiple routes (for example, both via capsules and colonoscopy during the same treatment) as well as in antibiotic-treated recipients with infectious diseases compared with antibiotic-naïve patients with noncommunicable diseases. Bacteroidetes and Actinobacteria species (including Bifidobacteria) displayed higher engraftment than Firmicutes except for six under-characterized Firmicutes species. Cross-dataset machine learning predicted the presence or absence of species in the post-FMT recipient at 0.77 average AUROC in leave-one-dataset-out evaluation, and highlighted the relevance of microbial abundance, prevalence and taxonomy to infer post-FMT species presence. By exploring the dynamics of microbiome engraftment after FMT and their association with clinical variables, our study uncovered species-specific engraftment patterns and presented machine learning models able to predict donors that might optimize post-FMT specific microbiome characteristics for disease-targeted FMT protocols.

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.

Gut microbiota-modulating agents in alcoholic liver disease: Links between host metabolism and gut microbiota

Alcoholic liver disease (ALD) involves a wide spectrum of diseases, including asymptomatic hepatic steatosis, alcoholic hepatitis, hepatic fibrosis, and cirrhosis, which leads to morbidity and mortality and is responsible for 0.9% of global deaths. Alcohol consumption induces bacterial translocation and alteration of the gut microbiota composition. These changes in gut microbiota aggravate hepatic inflammation and fibrosis. Alteration of the gut microbiota leads to a weakened gut barrier and changes host immunity and metabolic function, especially related to bile acid metabolism. Modulation and treatment for the gut microbiota in ALD has been studied using probiotics, prebiotics, synbiotics, and fecal microbial transplantation with meaningful results. In this review, we focused on the interaction between alcohol and gut dysbiosis in ALD. Additionally, treatment approaches for gut dysbiosis, such as abstinence, diet, pro-, pre-, and synbiotics, antibiotics, and fecal microbial transplantation, are covered here under ALD. However, further research through human clinical trials is warranted to evaluate the appropriate gut microbiota-modulating agents for each condition related to ALD.

Probing gut-brain links in Alzheimer's disease with rifaximin

Gut-microbiome-inflammation interactions have been linked to neurodegeneration in Alzheimer's disease (AD) and other disorders. We hypothesized that treatment with rifaximin, a minimally absorbed gut-specific antibiotic, may modify the neurodegenerative process by changing gut flora and reducing neurotoxic microbial drivers of inflammation. In a pilot, open-label trial, we treated 10 subjects with mild to moderate probable AD dementia (Mini-Mental Status Examination (MMSE) = 17 ± 3) with rifaximin for 3 months. Treatment was associated with a significant reduction in serum neurofilament-light levels (P < .004) and a significant increase in fecal phylum Firmicutes microbiota. Serum phosphorylated tau (pTau)181 and glial fibrillary acidic protein (GFAP) levels were reduced (effect sizes of -0.41 and -0.48, respectively) but did not reach statistical significance. In addition, there was a nonsignificant downward trend in serum cytokine interleukin (IL)-6 and IL-13 levels. Cognition was unchanged. Increases in stool Erysipelatoclostridium were correlated significantly with reductions in serum pTau181 and serum GFAP. Insights from this pilot trial are being used to design a larger placebo-controlled clinical trial to determine if specific microbial flora/products underlie neurodegeneration, and whether rifaximin is clinically efficacious as a therapeutic.

The role of the microbiota in the management of intensive care patients

The composition of the gut microbiota is highly dynamic and changes according to various conditions. The gut microbiota mainly includes difficult-to-cultivate anaerobic bacteria, hence knowledge about its composition has significantly arisen from culture-independent methods based on next-generation sequencing (NGS) such as 16S profiling and shotgun metagenomics. The gut microbiota of patients hospitalized in intensive care units (ICU) undergoes many alterations because of critical illness, antibiotics, and other ICU-specific medications. It is then characterized by lower richness and diversity, and dominated by opportunistic pathogens such as Clostridioides difficile and multidrug-resistant bacteria. These alterations are associated with an increased risk of infectious complications or death. Specifically, at the time of writing, it appears possible to identify distinct microbiota patterns associated with severity or infectivity in COVID-19 patients, paving the way for the potential use of dysbiosis markers to predict patient outcomes. Correcting the microbiota disturbances to avoid their consequences is now possible. Fecal microbiota transplantation is recommended in recurrent C. difficile infections and microbiota-protecting treatments such as antibiotic inactivators are currently being developed. The growing interest in the microbiota and microbiota-associated therapies suggests that the control of the dysbiosis could be a key factor in the management of critically ill patients. The present narrative review aims to provide a synthetic overview of microbiota, from healthy individuals to critically ill patients. After an introduction to the different techniques used for studying the microbiota, we review the determinants involved in the alteration of the microbiota in ICU patients and the latter's consequences. Last, we assess the means to prevent or correct microbiota alteration.

Microbiome therapeutics for hepatic encephalopathy

Hepatic encephalopathy (HE) is a complication of cirrhosis characterised by neuropsychiatric and motor dysfunction. Microbiota-host interactions play an important role in HE pathogenesis. Therapies targeting microbial community composition and function have been explored for the treatment of HE. Prebiotics, probiotics and faecal microbiota transplant (FMT) have been used with the aim of increasing the abundance of potentially beneficial taxa, while antibiotics have been used to decrease the abundance of potentially harmful taxa. Other microbiome therapeutics, including postbiotics and absorbents, have been used to target microbial products. Microbiome-targeted therapies for HE have had some success, notably lactulose and rifaximin, with probiotics and FMT also showing promise. However, there remain several challenges to the effective application of microbiome therapeutics in HE, including the resilience of the microbiome to sustainable change and unpredictable clinical outcomes from microbiota alterations. Future work in this space should focus on rigorous trial design, microbiome therapy selection, and a personalised approach to HE.

The Dilemma of Persistent Irritable Bowel Syndrome Symptoms in Patients with Quiescent Inflammatory Bowel Disease

Irritable bowel syndrome and inflammatory bowel disease differ in their natural evolution, etiopathogenesis, diagnostic criteria, and therapeutic approach. However, recent evidence has suggested some similarities in mechanisms underlying symptom development and progression. There is a relevant role for alterations in the microbiome-brain-gut axis in both diseases. The presence of irritable bowel syndrome symptoms in patients with quiescent inflammatory bowel disease is common in clinical practice. To determine the cause of irritable bowel syndrome symptoms in patients with quiescent inflammatory bowel disease is a clinical challenge. This review aims to illustrate possible causes and solutions for these patients.

Phenyl lactic acid alleviates Samonella Typhimurium-induced colitis via regulating microbiota composition, SCFA production and inflammatory responses

Colitis caused by non-typhoidal Salmonella (NST) infection is increasingly serious and widespread, so new effective treatment strategies with little or no side-effects are urgently needed. Our previous research found that phenyl lactic acid (PLA) derived from Lactobacillus plantarum ZJ316 can effectively inhibit Salmonella enterica Typhimurium (S. Typhimurium). In this study, we further investigated the protective effects of this PLA against S. Typhimurium-induced colitis in mice. An infection model was established using female C57BL/6J mice by oral administration of 109 CFU mL-1 of S. Typhimurium, and PLA was supplied for 10 days after infection. In colitic mice, PLA administration reduced the disease activity index, prevented the colon shortening and spleen enlargement, decreased liver enzyme (AST and ALT) activities, and alleviated the colonic tissue damage. RT-qPCR analysis showed that PLA significantly down-regulated the levels of NF-κB, TLR4 and pro-inflammatory cytokines (IFN-γ, IL-1β and TNF-α), but stimulated the mRNA expression of the anti-inflammatory cytokine IL-10. Changes in intestinal microecology were analyzed by 16S rRNA sequencing. PLA modulated colonic microbiota dysbiosis by increasing the abundance of Lactobacillus, Butyricicoccus and Roseburia, and reducing Salmonella and Alloprevotella at the genus level. In addition, PLA significantly increased the concentrations of short-chain fatty acids (SCFAs) in the colon, especially propionic acid and butyric acid. These findings revealed that PLA has potential benefits on alleviating S. Typhimurium-induced colitis mainly through intestinal microbiota regulation and inflammation elimination, providing a new perspective for the NTS infection treatment strategy.

Antibiotics: Conventional Therapy and Natural Compounds with Antibacterial Activity-A Pharmaco-Toxicological Screening

Antibiotics are considered as a cornerstone of modern medicine and their discovery offers the resolution to the infectious diseases problem. However, the excessive use of antibiotics worldwide has generated a critical public health issue and the bacterial resistance correlated with antibiotics inefficiency is still unsolved. Finding novel therapeutic approaches to overcome bacterial resistance is imperative, and natural compounds with antibacterial effects could be considered a promising option. The role played by antibiotics in tumorigenesis and their interrelation with the microbiota are still debatable and are far from being elucidated. Thus, the present manuscript offers a global perspective on antibiotics in terms of evolution from a historical perspective with an emphasis on the main classes of antibiotics and their adverse effects. It also highlights the connection between antibiotics and microbiota, focusing on the dual role played by antibiotics in tumorigenesis. In addition, using the natural compounds with antibacterial properties as potential alternatives for the classical antibiotic therapy is discussed.

Gut microbiota mediated molecular events and therapy in liver diseases

Gut microbiota is a community of microorganisms that reside in the gastrointestinal tract. An increasing number of studies has demonstrated that the gut-liver axis plays a critical role in liver homeostasis. Dysbiosis of gut microbiota can cause liver diseases, including nonalcoholic fatty liver disease and alcoholic liver disease. Preclinical and clinical investigations have substantiated that the metabolites and other molecules derived from gut microbiota and diet interaction function as mediators to cause liver fibrosis, cirrhosis, and final cancer. This effect has been demonstrated to be associated with dysregulation of intrahepatic immunity and liver metabolism. Targeting these findings have led to the development of novel preventive and therapeutic strategies. Here, we review the cellular and molecular mechanisms underlying gut microbiota-mediated impact on liver disease. We also summarize the advancement of gut microbiota-based therapeutic strategies in the control of liver diseases.

Rifaximin-Alpha and Other Crystalline Forms of Rifaximin: Are There Any Differences?

Rifaximin is an antibiotic characterized by polymorphism. It has various crystalline forms with different pharmacological characteristics. Rifaximin acts locally in the digestive tract, therefore it is important for the absorption to be minimal and for concentration in the intestinal lumen to be high. The absorption of other crystalline forms of rifaximin in the intestine is greater than that of rifaximin-α (Alpha Normix®). Differences in pharmacokinetics of the crystalline forms of rifaximin may affect its effectiveness and safety, especially in patients with chronic diseases (immunodeficiency and leaky gut against the background of liver cirrhosis) who require long courses of therapy. Rifaximin-α (Alpha Normix®) is unique as it has eubiotic and anti-inflammatory properties in addition to local antibacterial effect. Given its diverse mechanisms of action, rifaximin-α positively modulates gut microbiota.

QTL-Seq identifies quantitative trait loci of relative electrical conductivity associated with heat tolerance in bottle gourd (Lagenaria siceraria)

Heat is a major abiotic stress that seriously affects watermelon (Citrullus lanatus) production. However, its effects may be mitigated through grafting watermelon to heat tolerant bottle gourd (Lagenaria siceraria) rootstocks. Understanding the genetic basis of heat tolerance and development of reliable DNA markers to indirectly select for the trait are necessary in breeding for new varieties with heat tolerance. The objectives of this study were to investigate the inheritance of heat tolerance and identify molecular markers associated with heat tolerance in bottle gourd. A segregating F₂ population was developed from a cross between two heat tolerant and sensitive inbred lines. The population was phenotyped for relative electrical conductivity (REC) upon high temperature treatment which was used as an indicator for heat tolerance. QTL-seq was performed to identify regions associated with heat tolerance. We found that REC-based heat tolerance in this population exhibited recessive inheritance. Seven heat-tolerant quantitative trait loci (qHT1.1, qHT2.1, qHT2.2, qHT5.1, qHT6.1, qHT7.1, and qHT8.1) were identified with qHT2.1 being a promising major-effect QTL. In the qHT2.1 region, we identified three non-synonymous SNPs that were potentially associated with heat tolerance. These SNPs were located in the genes that may play roles in pollen sterility, intracellular transport, and signal recognition. Association of the three SNPs with heat tolerance was verified in segregating F₂ populations, which could be candidate markers for marker assisted selection for heat tolerance in bottle gourd. The qHT2.1 region is an important finding that may be used for fine mapping and discovery of novel genes associated with heat tolerance in bottle gourd.

Short-course Rifaximin therapy efficacy and lactulose hydrogen breath test in Chinese patients with diarrhea-predominant irritable bowel syndrome

Background

Gut microbiota alterations including small intestinal bacterial overgrowth (SIBO) might play a role in pathogenesis of irritable bowel syndrome (IBS). Rifaximin could effectively and safely improve IBS symptoms. The aim of this study was to investigate the effect of rifaximin on Gastrointestinal (GI) symptoms, quality of life (QOL) and SIBO eradication in Chinese IBS-D patients.

Methods

This study included 78 IBS-D patients defined by the Rome IV criteria. Patients received 400 mg rifaximin twice daily for 2 weeks and 10-week follow-up. GI symptoms were assessed at week 0, 2, 4, 8 and 12. QOL and lactulose hydrogen breath test (LHBT) results were estimated at week 0 and 4.

Results

All participants showed significant improvements in GI symptom subdomains after rifaximin treatment (all P < 0.05), which could maintain at least 10 weeks of follow-up. Additionally, QOL scores were increased with concomitant improvement of clinical symptoms (all P < 0.05). The 45 rifaximin-responsive patients (57.7%) achieved significantly greater GI-symptom improvement than non-responders (all P < 0.05). No GI symptoms were associated with SIBO (all P > 0.05). SIBO normalization after rifaximin treatment measured by LHBT was found in 44.4% (20/45) of patients with SIBO before treatment.

Conclusion

A short course (2 weeks) of rifaximin improved GI symptoms and QOL in Chinese IBS-D patients whether they had SIBO or not. However, the efficacy of rifaximin could not be explained by the successful eradication of SIBO. Further studies on the therapeutic mechanisms of rifaximin in IBS are urgently needed.

Evaluation of a Dual-Acting Antibacterial Agent, TNP-2092, on Gut Microbiota and Potential Application in the Treatment of Gastrointestinal and Liver Disorders

TNP-2092 is a unique multitargeting drug conjugate with extremely low propensity for development of resistance. The in vitro activity of TNP-2092 against a panel of urease-producing bacteria was similar to that of rifaximin, a locally acting antibiotic approved for the treatment of hepatic encephalopathy, irritable bowel syndrome with diarrhea, and traveler's diarrhea. When given orally, TNP-2092 exhibited low absorption and the majority of compound was recovered in feces as parent. The impact of oral TNP-2092 on gut microbiota was investigated in rats. TNP-2092 was administered to rats by oral gavage for 7 days. Feces samples were collected and analyzed by 16S rRNA sequencing. Although the total amount of bacterial load appeared relatively unchanged before, during, and after treatment, significant changes in the relative abundance of certain gut bacteria at family and genus levels were observed. Some of the changes are known to be associated with improvement of symptoms associated with liver cirrhosis and hepatic encephalopathy. The observed effects of TNP-2092 on gut microbiota in rats were similar to those of rifaximin. In vivo, TNP-2092 demonstrated potent efficacy in a mouse Clostridium difficile infection model, superior to metronidazole and vancomycin, with no relapse observed after treatment. TNP-2092 is currently in clinical development for the treatment of symptoms associated with gastrointestinal and liver disorders.

Bacillus coagulans (PROBACI) in treating constipation-dominant functional bowel disorders

Bacillus coagulans (PROBACI) bacteria have been examined for efficacy against infectious or inflammatory bowel diseases. The aim of this observational and cross-sectional study was to evaluate the effects of PROBACI against various functional bowel symptoms.Thirty-eight enrolled patients (36.5 ± 12.6 years) with functional bowel disorders in a gastrointestinal clinic were administered PROBACI (300-mg formulation containing 1 × 10 colony-forming units of B coagulans) twice/day over a 4-week period. Abdominal pain, abdominal distention, and global assessment were evaluated using a 5-point visual analog scale. The defecation characteristics, discomfort level, and effort required for defecation were recorded. The gut-microbiota composition in terms of the Firmicutes/Bacteroidetes ratio was analyzed by 16S-ribosomal RNA gene sequencing with stool samples at days 0, 14, and 28 post-treatment.The 38 patients achieved significant improvements in abdominal pain (2.8 ± 0.5 to 3.3 ± 0.7, P = .0009), abdominal distention (2.5 ± 0.7 to 3.2 ± 0.8, P = .0002), and global assessment (2.7 ± 0.6 to 3.6 ± 0.7, P = .0001) from days 0 to 14. Compared with the diarrhea group, the constipation group achieved greater improvements in terms of discomfort during defecation (2.5 ± 0.7 to 3.1 ± 0.7, P = .02) and normalization of defecation style (50% vs 7.1%, P = .007) by day 28. A difference was observed in the Firmicutes/Bacteroidetes ratio between the constipation-dominant group (118.0) and diarrhea-dominant group (319.2), but this difference was not significant.PROBACI provided control of abdominal pain, less discomfort during defecation, and a more normalized defecation style, especially in the constipation-dominant group.

Abdominal Pain Response to Rifaximin in Patients With Irritable Bowel Syndrome With Diarrhea

INTRODUCTION

Abdominal pain is the principal symptom of irritable bowel syndrome (IBS). This analysis examined abdominal pain response in adults with IBS with diarrhea (IBS-D) receiving the nonsystemic antibiotic rifaximin.

METHODS

In the Targeted Nonsystemic Antibiotic Rifaximin Gut-Selective Evaluation of Treatment for IBS-D 3 trial, adults with IBS-D received open-label rifaximin 550 mg 3 times daily for 2 weeks, followed by the 4-week post-treatment phase assessing abdominal pain and stool consistency response. Responders were followed for up to 18 additional weeks; patients with recurrence were randomly assigned to receive two 2-week courses of double-blind rifaximin 550 mg 3 times daily or placebo, separated by 10 weeks. Analyses evaluated mean weekly improvements from baseline (e.g., ≥30%, ≥40%, and ≥50%) in abdominal pain during the 4-week post-repeat-treatment phases.

RESULTS

Of the 2,438 evaluable patients, 1,384 (56.8%) had abdominal pain response to open-label rifaximin (≥30% improvement from baseline in the mean weekly abdominal pain score during ≥2 of the first 4 weeks post-treatment). Weekly decrease (improvement) in responders' mean abdominal pain score (scale range, 0-10) from baseline ranged from -2.6 to -3.3 points during the 18-week follow-up. After the first double-blind repeat treatment, a significantly higher percentage of rifaximin-treated patients were abdominal pain responders (53.9% [172/319]) vs placebo (44.4% [134/302], P = 0.02), with similar results after the second repeat treatment (52.9% [155/293] vs 44.7% [123/275], respectively, P = 0.047). A significantly higher percentage of rifaximin-treated patients were weekly abdominal pain responders for ≥50% of the 18-week double-blind repeat treatment phase (47.9% [138/288] vs 35.9% [97/270], P = 0.004).

DISCUSSION

Rifaximin is efficacious in improving abdominal pain in adults with IBS-D.

Gastrointestinal (non-systemic) antibiotic rifaximin differentially affects chronic stress-induced changes in colon microbiome and gut permeability without effect on behavior

Chronic stress is often accompanied by gastrointestinal symptoms, which might be due to stress-induced shift of gut microbiome to pathogenic bacteria. It has been hypothesized that stress alters gut permeability and results in mild endotoxemia which exaggerates HPA activity and contributes to anxiety and depression. To reveal the relationship between microbiome composition, stress-induced gastrointestinal functions and behavior, we treated chronically stressed mice with non-absorbable antibiotic, rifaximin. The "two hits" stress paradigm was used, where newborn mice were separated from their mothers for 3 h daily as early life adversity (maternal separation, MS) and exposed to 4 weeks chronic variable stress (CVS) as adults. 16S rRNA based analysis of gut microbiome revealed increases of Bacteroidetes and Proteobacteria and more specifically, Clostridium species in chronically stressed animals. In mice exposed to MS + CVS, we found extenuation of colonic mucosa, increased bacterial translocation to mesenteric lymph node, elevation of plasma LPS levels and infiltration of F4/80 positive macrophages into the colon lamina propria. Chronically stressed mice displayed behavioral signs of anxiety-like behavior and neophobia. Rifaximin treatment decreased Clostridium concentration, gut permeability and LPS plasma concentration and increased colonic expression of tight junction proteins (TJP1, TJP2) and occludin. However, these beneficial effects of rifaximin in chronically stressed mice was not accompanied by positive changes in behavior. Our results suggest that non-absorbable antibiotic treatment alleviates stress-induced local pathologies, however, does not affect stress-induced behavior.

Effects of Antibiotic Pretreatment of an Ulcerative Colitis-Derived Fecal Microbial Community on the Integration of Therapeutic Bacteria In Vitro

Fecal microbiota transplantation (FMT) is a proposedly useful strategy for the treatment of gastrointestinal (GI) disorders through remediation of the patient gut microbiota. However, its therapeutic success has been variable, necessitating research to uncover mechanisms that improve patient response. Antibiotic pretreatment has been proposed as one method to enhance the success rate by increasing niche availability for introduced species. Several limitations hinder exploring this hypothesis in clinical studies, such as deleterious side effects and the development of antimicrobial resistance in patients. Thus, the purpose of this study was to evaluate the use of an in vitro, bioreactor-based, colonic ecosystem model as a form of preclinical testing by determining how pretreatment with the antibiotic rifaximin influenced engraftment of bacterial strains sourced from a healthy donor into an ulcerative colitis-derived defined microbial community. Distinct species integrated under the pretreated and untreated conditions, with the relative rifaximin resistance of the microbial strains being an important influencer. However, both conditions resulted in the integration of taxa from Clostridium clusters IV and XIVa, a concomitant reduction of Proteobacteria, and similar decreases in metabolites associated with poor health status. Our results agree with the findings of similar research in the clinic by others, which observed no difference in primary patient outcomes whether or not patients were given rifaximin prior to FMT. We therefore conclude that our model is useful for screening for antibiotics that could improve efficacy of FMT when used as a pretreatment.IMPORTANCE Patients with gastrointestinal disorders often exhibit derangements in their gut microbiota, which can exacerbate their symptoms. Replenishing these ecosystems with beneficial bacteria through fecal microbiota transplantation is thus a proposedly useful therapeutic; however, clinical success has varied, necessitating research into strategies to improve outcomes. Antibiotic pretreatment has been suggested as one such approach, but concerns over harmful side effects have hindered testing this hypothesis clinically. Here, we evaluate the use of bioreactors supporting defined microbial communities derived from human fecal samples as models of the colonic microbiota in determining the effectiveness of antibiotic pretreatment. We found that relative antimicrobial resistance was a key determinant of successful microbial engraftment with rifaximin (broad-spectrum antibiotic) pretreatment, despite careful timing of the application of the therapeutic agents, resulting in distinct species profiles from those of the control but with similar overall outcomes. Our model had results comparable to the clinical findings and thus can be used to screen for useful antibiotics.

Mechanism of action and therapeutic benefit of rifaximin in patients with irritable bowel syndrome: a narrative review

Irritable bowel syndrome (IBS) is a common functional gastrointestinal disorder with a multifactorial pathophysiology. The gut microbiota differs between patients with IBS and healthy individuals. After a bout of acute gastroenteritis, postinfection IBS may result in up to approximately 10% of those affected. Small intestinal bacterial overgrowth (SIBO) is more common in patients with IBS than in healthy individuals, and eradication of SIBO with systemic antibiotics has decreased symptoms of IBS in some patients with IBS and SIBO. The nonsystemic (i.e. low oral bioavailability) antibiotic rifaximin is indicated in the United States and Canada for the treatment of adults with IBS with diarrhea (IBS-D). The efficacy and safety of 2-week single and repeat courses of rifaximin have been demonstrated in randomized, placebo-controlled studies of adults with IBS. Rifaximin is widely thought to exert its beneficial clinical effects in IBS-D through manipulation of the gut microbiota. However, current studies indicate that rifaximin induces only modest effects on the gut microbiota of patients with IBS-D, suggesting that the efficacy of rifaximin may involve other mechanisms. Indeed, preclinical data reveal a potential role for rifaximin in the modulation of inflammatory cytokines and intestinal permeability, but these two findings have not yet been examined in the context of clinical studies. The mechanism of action of rifaximin in IBS is likely multifactorial, and further study is needed.

Rifaximin improves survival in cirrhotic patients with refractory ascites: A real-world study

BACKGROUND

Rifaximin has been shown to reduce the incidence of hepatic encephalopathy and other complications in patients with cirrhosis. However, few studies have investigated the effect of rifaximin in cirrhotic patients with refractory ascites.

AIM

To evaluate the effects of rifaximin in the treatment of refractory ascites and to preliminarily explore its possible mechanism.

METHODS

A total of 75 cirrhotic patients with refractory ascites were enrolled in the study (50 in a rifaximin and 25 in a control group). Patients in the rifaximin group were divided into two subgroups according to the presence of spontaneous bacterial peritonitis and treatment with or without other antibiotics (19 patients treated with rifaximin and 31 patients treated with rifaximin plus intravenous antibiotics). All patients received conventional treatment for refractory ascites, while patients in the rifaximin group received oral rifaximin-α 200 mg four times daily for at least 2 wk. The ascites grade, fasting weight, liver and kidney function, and inflammatory factors in the plasma were evaluated before and after treatment. In addition, the gut microbiota was determined by metagenomics sequencing to analyse the changes in the characteristics of the gut microbiota before and after rifaximin treatment. The patients were followed for 6 mo.

RESULTS

Compared with the control group, the fasting weight of patients significantly decreased and the ascites significantly subsided after treatment with rifaximin (P = 0.011 and 0.009, respectively). The 6-mo survival rate of patients in the rifaximin group was significantly higher than that in the control group (P = 0.048). The concentration of interferon-inducible protein 10 decreased significantly in the rifaximin group compared with that in the control group (P = 0.024). The abundance of Roseburia, Haemophilus, and Prevotella was significantly reduced after rifaximin treatment, while the abundance of Lachnospiraceae_noname, Subdoligranulum, and Dorea decreased and the abundance of Coprobacillus increased after treatment with rifaximin plus intravenous antibiotics. The gene expression of virulence factors was significantly reduced after treatment in both subgroups treated with rifaximin or rifaximin plus intravenous antibiotics.

CONCLUSION

Rifaximin mitigates ascites and improves survival of cirrhotic patients with refractory ascites. A possible mechanism is that rifaximin regulates the structure and function of intestinal bacteria, thus improving the systemic inflammatory state.

Rifaximin improves survival in cirrhotic patients with refractory ascites: A real-world study

BACKGROUND

Rifaximin has been shown to reduce the incidence of hepatic encephalopathy and other complications in patients with cirrhosis. However, few studies have investigated the effect of rifaximin in cirrhotic patients with refractory ascites.

AIM

To evaluate the effects of rifaximin in the treatment of refractory ascites and to preliminarily explore its possible mechanism.

METHODS

A total of 75 cirrhotic patients with refractory ascites were enrolled in the study (50 in a rifaximin and 25 in a control group). Patients in the rifaximin group were divided into two subgroups according to the presence of spontaneous bacterial peritonitis and treatment with or without other antibiotics (19 patients treated with rifaximin and 31 patients treated with rifaximin plus intravenous antibiotics). All patients received conventional treatment for refractory ascites, while patients in the rifaximin group received oral rifaximin-α 200 mg four times daily for at least 2 wk. The ascites grade, fasting weight, liver and kidney function, and inflammatory factors in the plasma were evaluated before and after treatment. In addition, the gut microbiota was determined by metagenomics sequencing to analyse the changes in the characteristics of the gut microbiota before and after rifaximin treatment. The patients were followed for 6 mo.

RESULTS

Compared with the control group, the fasting weight of patients significantly decreased and the ascites significantly subsided after treatment with rifaximin (P = 0.011 and 0.009, respectively). The 6-mo survival rate of patients in the rifaximin group was significantly higher than that in the control group (P = 0.048). The concentration of interferon-inducible protein 10 decreased significantly in the rifaximin group compared with that in the control group (P = 0.024). The abundance of Roseburia, Haemophilus, and Prevotella was significantly reduced after rifaximin treatment, while the abundance of Lachnospiraceae_noname, Subdoligranulum, and Dorea decreased and the abundance of Coprobacillus increased after treatment with rifaximin plus intravenous antibiotics. The gene expression of virulence factors was significantly reduced after treatment in both subgroups treated with rifaximin or rifaximin plus intravenous antibiotics.

CONCLUSION

Rifaximin mitigates ascites and improves survival of cirrhotic patients with refractory ascites. A possible mechanism is that rifaximin regulates the structure and function of intestinal bacteria, thus improving the systemic inflammatory state.

Clinical Management of the Microbiome in Irritable Bowel Syndrome

Background

A growing body of evidence suggests that dysbiosis contributes to the onset and symptomatology of irritable bowel syndrome (IBS) and other functional bowel disorders. Changes to the gastrointestinal microbiome may contribute to the underlying pathophysiology of IBS.

Methods

The present review summarizes the potential effects of microbiome changes on GI transit, intestinal barrier function, immune dysregulation and inflammation, gut–brain interactions and neuropsychiatric function.

Results

A multimodal approach to IBS management is recommended in accordance with current Canadian guidelines. Pharmacologic treatments are advised to target the presumed underlying pathophysiological mechanism, such as dysregulation of GI transit, peristalsis, intestinal barrier function and pain signalling. The management plan for IBS may also include treatments directed at dysbiosis, including dietary modification and use of probiotics, which may promote the growth of beneficial bacteria, affect intestinal gas production and modulate the immune response; and the administration of periodic short courses of a nonsystemic antibiotic such as rifaximin, which may re-establish microbiota diversity and improve IBS symptoms.

Conclusion

Dysregulated host–microbiome interactions are complex and the use of microbiome-directed therapies will necessarily be empiric in individual patients. A management algorithm comprising microbiome- and nonmicrobiome-directed therapies is proposed.

Four Weeks of Treatment With Rifaximin Fails to Significantly Alter Microbial Diversity in Rectal Samples of HIV-Infected Immune Non-Responders (ACTG A5286) Which May be Attributed to Rectal Swab Use

INTRODUCTION

HIV-infected individuals have evidence of intestinal microbial translocation which is associated with immune activation and unfavorable clinical outcomes. Rifaximin, a non-absorbable antibiotic which reduces microbial translocation in other disease states, was shown to have a marginal beneficial effect on microbial translocation, T-cell activation, and inflammation in a multisite randomized trial (ACTG A5286; NCT01466595) of HIV-infected persons with poor immunologic recovery receiving ART. Here, we report analysis of the rectal microbiome changes associated with that trial.

METHODS

HIV-1-infected individuals receiving ART with CD4-T cell count < 350cells/mm3 and viral suppression were randomized 2:1 to rifaximin or no therapy for 4 weeks. Rectal swabs were collected at baseline (pre-treatment) and at week 4 of rifaximin therapy. Genomic DNA extracted from rectal swab samples was analyzed using high throughput sequencing and quantitative PCR of bacterial 16S ribosomal RNA (rRNA) genes.

RESULTS

Forty-eight HIV-infected participants (31 received rifaximin, 17 no treatment) were included. There was broad variability in the recovery of bacterial rRNA from the specimens at baseline. No major significant (FDR P < 0.05) effects of rifaximin treatment on alpha- or beta-diversity or individual taxa were observed between or within the treatment arms, with analyses conducted at taxonomic levels from phylum to genus.

CONCLUSIONS

Rifaximin did not meaningfully alter the diversity or composition of the rectal microbiome of HIV-infected individuals after 4 weeks of therapy, although rectal swab specimens varied widely in their microbial load.

Small Intestinal Bacterial Overgrowth in Children: A State-Of-The-Art Review

Small intestinal bacterial overgrowth (SIBO) is a heterogenous and poorly understood entity characterised by an excessive growth of select microorganisms within the small intestine. This excessive bacterial biomass, in turn, disrupts host physiology in a myriad of ways, leading to gastrointestinal and non-gastrointestinal symptoms and complications. SIBO is a common cause of non-specific gastrointestinal symptoms in children, such as chronic abdominal pain, abdominal distention, diarrhoea, and flatulence, amongst others. In addition, it has recently been implicated in the pathophysiology of stunting, a disease that affects millions of children worldwide. Risk factors such as acid-suppressive therapies, alterations in gastrointestinal motility and anatomy, as well as impoverished conditions, have been shown to predispose children to SIBO. SIBO can be diagnosed via culture-dependant or culture-independent approaches. SIBO's epidemiology is limited due to the lack of uniformity and consensus of its diagnostic criteria, as well as the paucity of literature available. Antibiotics remain the first-line treatment option for SIBO, although emerging modalities such as probiotics and diet manipulation could also have a role. Herein, we present a state-of-the-art-review which aims to comprehensively outline the most current information on SIBO in children, with particular emphasis on the gut microbiota.

Systematic review with meta-analysis: efficacy of faecal microbiota transplantation for the treatment of irritable bowel syndrome

BACKGROUND

Increasing evidence supports the role of the gut microbiota in the aetiology of irritable bowel syndrome (IBS). Faecal microbiota transplantation (FMT) is a highly effective treatment against recurrent Clostridioides difficile infection in randomised controlled trials (RCTs), and may be beneficial in ulcerative colitis. However, its efficacy in IBS is uncertain.

AIM

To perform a systematic review and meta-analysis to examine this issue.

METHODS

We searched MEDLINE, EMBASE, EMBASE Classic, the Cochrane Central Register of Controlled Trials, and clinicaltrials.gov through to March 2019. RCTs recruiting adults with IBS, which compared FMT with placebo, were eligible. Dichotomous symptom data were pooled to obtain a relative risk (RR) of remaining symptomatic after therapy, with a 95% CI.

RESULTS

The search strategy identified 322 citations. Five RCTs were eligible for inclusion, containing 267 patients. Overall, 92.2% of included patients had IBS-D or IBS-M, and only 7.8% IBS-C. When data were pooled for all patients, irrespective of stool type, the RR of IBS symptoms not improving was 0.98 (95% CI 0.58-1.66). Placebo capsules administered orally were superior to capsules containing donor stool in two pooled trials (RR = 1.96; 95% CI 1.19-3.20). FMT from donor stool delivered via colonoscopy was superior to autologous stool in two pooled RCTs (RR = 0.63; 95% CI 0.43-0.93). FMT from donor stool via nasojejunal tube showed a trend towards a benefit over autologous stool in one trial (RR = 0.69; 95% CI 0.46-1.02).

CONCLUSIONS

Fresh or frozen donor stool delivered via colonoscopy or nasojejunal tube may be beneficial in IBS. Larger, more rigorously conducted trials of FMT in IBS are needed.

Follow-on RifAximin for the Prevention of recurrence following standard treatment of Infection with Clostridium Difficile (RAPID): a randomised placebo controlled trial

BACKGROUND

Clostridium difficile infection (CDI) recurs after initial treatment in approximately one in four patients. A single-centre pilot study suggested that this could be reduced using 'follow-on' rifaximin treatment. We aimed to assess the efficacy of rifaximin treatment in preventing recurrence.

METHODS

A multisite, parallel group, randomised, placebo controlled trial recruiting patients aged ≥18 years immediately after resolution of CDI through treatment with metronidazole or vancomycin. Participants received either rifaximin 400 mg three times a day for 2 weeks, reduced to 200 mg three times a day for a further 2 weeks or identical placebo. The primary endpoint was recurrence of CDI within 12 weeks of trial entry.

RESULTS

Between December 2012 and March 2016, 151 participants were randomised to either rifaximin or placebo. Primary outcome data were available on 130. Mean age was 71.9 years (SD 15.3). Recurrence within 12 weeks was 29.5% (18/61) among participants allocated to placebo compared with 15.9% (11/69) among those allocated to rifaximin, a difference between groups of 13.7% (95% CI -28.1% to 0.7%, p=0.06). The risk ratio was 0.54 (95% CI 0.28 to 1.05, p=0.07). During 6-month safety follow-up, nine participants died in each group (12%). Adverse event rates were similar between groups.

CONCLUSION

While 'follow-on' rifaximin after CDI appeared to halve recurrence rate, we failed to reach our recruitment target in this group of frail elderly patients, so the estimated effect of rifaximin lacks precision. A meta-analysis including a previous trial suggests that rifaximin may be effective; however, further, larger confirmatory studies are needed.

Cyclic rifaximin and soluble dietary fiber therapy for symptomatic diverticular disease: effective prevention of complications

The article discusses the current issues of managing patients with colonic diverticular disease. The prevalence of pathology is steadily increasing, which is due to the more frequent diagnosis of the disease and the increase in life expectancy of the population. Meanwhile, the wrong approaches to the management of this category of patients can result in the development of serious complications that often result in fatal outcomes. The paper presents data on the efficacy of rifaximin therapy of colonic diverticular disease, including using cyclic courses that significantly reduce the risk of complications. Particular attention is paid to the role of dietary fiber in the prevention of the inflammation development in the diverticular disease, including dietary fiber combined with rifaximin.

Irritable bowel syndrome and colonic diverticular disease: overlapping symptoms and overlapping therapeutic approaches

PURPOSE OF REVIEW

Irritable bowel syndrome (IBS) is a common symptomatic disorder in the Western world and colonic diverticula are also prevalent; however, relationships between IBS-type symptoms and diverticula have been a source of much debate. Our goal was to reassess these relationships in the light of new data.

RECENT FINDINGS

On removing from consideration clinical scenarios which are directly related to diverticula (i.e., diverticulitis, diverticular hemorrhage, and complications of diverticulitis, such as stricture and fistula), relationships between IBS and diverticula can be seen to revolve around a number of questions. First, are IBS and symptomatic uncomplicated diverticular disease (SUDD) the same condition? Or, in other words is SUDD no more than IBS in an individual who just happens to have diverticula? Although coincident IBS and diverticula inevitably do occur there is some evidence to indicate that SUDD may be somewhat distinctive with SUDD being characterized by more frequent and severe pain. Second, and analogous to interactions between IBS and inflammatory bowel disease or celiac disease, can an episode of acute diverticulitis lead to the de novo development of IBS? There is now epidemiological and pathophysiological evidence to support this occurrence.

SUMMARY

Although relationships between uncomplicated diverticular disease and IBS have been reexamined their status remains unclear. As yet, however, none of the newer concepts related to this relationship have led to new therapeutic approaches in IBS or diverticular disease.

Systematic review with meta-analysis: the efficacy of prebiotics, probiotics, synbiotics and antibiotics in irritable bowel syndrome

BACKGROUND

Irritable bowel syndrome (IBS) is a chronic functional bowel disorder. Disturbances in the gastrointestinal microbiome may be involved in its aetiology.

AIM

To perform a systematic review and meta-analysis to examine the efficacy of prebiotics, probiotics, synbiotics and antibiotics in IBS.

METHODS

MEDLINE, EMBASE, and the Cochrane Controlled Trials Register were searched (up to July 2017). Randomised controlled trials (RCTs) recruiting adults with IBS, comparing prebiotics, probiotics, synbiotics or antibiotics with placebo or no therapy were eligible. Dichotomous symptom data were pooled to obtain a relative risk (RR) of remaining symptomatic after therapy, with a 95% confidence interval (CI). Continuous data were pooled using a standardised mean difference with a 95% CI.

RESULTS

The search identified 4017 citations. Data for prebiotics and synbiotics were sparse. Fifty-three RCTs of probiotics, involving 5545 patients, were eligible. Particular combinations of probiotics, or specific species and strains, appeared to have beneficial effects on global IBS symptoms and abdominal pain, but it was not possible to draw definitive conclusions about their efficacy. There were five trials of similar design that used rifaximin in non-constipated IBS patients, which was more effective than placebo (RR of symptoms persisting = 0.84; 95% CI 0.79-0.90). Adverse events were no more common with probiotics or antibiotics.

CONCLUSIONS

Which particular combination, species or strains of probiotics are effective for IBS remains, for the most part, unclear. Rifaximin has modest efficacy in improving symptoms in non-constipated IBS.

Clinical Response of Rifaximin Treatment in Patients with Abdominal Bloating

BACKGROUND/AIMS

Abdominal bloating is a troublesome complaint due to insufficient understanding of the pathophysiology. The aim of this study was to evaluate the efficacy of rifaximin in reducing bloating associated with functional gastrointestinal disorders (FGIDs).

METHODS

A total of 63 patients were treated with rifaximin for FGIDs with bloating or gas-related symptoms between 2007 and 2013 at Seoul National University Bundang Hospital. Rifaximin was administered at a dose between 800 mg/day and 1,200 mg/day for 5 to 14 days. The proportion of patients who had adequate relief of global FGID symptoms and FGID-related bloating was retrospectively assessed. The response was recorded when the symptoms were reduced by at least 50% at the follow-up after treatment cessation.

RESULTS

The mean age was 56.8±14.2 years; 49.2% were females. According to Rome III criteria, 20.6% (13/63) had irritable bowel syndrome (IBS) with constipation, 9.5% (6/63) had IBS with diarrhea, 4.8% (3/63) had mixed IBS, 23.8% (15/63) had functional dyspepsia, and 12.7% (8/63) had functional bloating. Of the 51 subjects who were followed-up, 30 (58.8%) had adequate relief of global FGID symptoms and 26 (51.0%) experienced improvement of abdominal bloating after rifaximin treatment. The proportion of female was slightly higher in non-response group than in the response group (60.0% vs. 34.6%, p=0.069). Otherwise, there was no difference between the two groups.

CONCLUSIONS

Despite the limitations of this retrospective study, our data confirms that rifaximin may be beneficial for abdominal bloating. Further prospective clinical trial with a larger cohort is needed.

Short-course therapy for diarrhea-predominant irritable bowel syndrome: understanding the mechanism, impact on gut microbiota, and safety and tolerability of rifaximin

Irritable bowel syndrome (IBS) is a common gastrointestinal (GI) disorder characterized by abdominal pain that occurs with defecation or alterations in bowel habits. Further classification is based on the predominant bowel habit: constipation-predominant IBS, diarrhea-predominant IBS (IBS-D), or mixed IBS. The pathogenesis of IBS is unclear and is considered multifactorial in nature. GI dysbiosis, thought to play a role in IBS pathophysiology, has been observed in patients with IBS. Alterations in the gut microbiota are observed in patients with small intestinal bacterial overgrowth, and overgrowth may occur in a subset of patients with IBS. The management of IBS includes therapies targeting the putative factors involved in the pathogenesis of the condition. However, many of these interventions (eg, eluxadoline and alosetron) require long-term, daily administration and have important safety considerations. Agents thought to modulate the gut microbiota (eg, antibiotics and probiotics) have shown potential benefits in clinical studies. However, conventional antibiotics (eg, neomycin) are associated with several adverse events and/or the risk of bacterial antibiotic resistance, and probiotics lack uniformity in composition and consistency of response in patients. Rifaximin, a nonsystemic antibiotic administered as a 2-week course of therapy, has been shown to be safe and efficacious for the treatment of IBS-D. Rifaximin exhibits a favorable benefit-to-harm ratio when compared with daily therapies for IBS-D (eg, alosetron and tricyclic antidepressants), and rifaximin was not associated with the emergence of bacterial antibiotic resistance. Thus, short-course therapy with rifaximin is an appropriate treatment option for IBS-D.

New concepts on intestinal microbiota and the role of the non-absorbable antibiotics with special reference to rifaximin in digestive diseases

Digestive diseases are a broad range of chronic disorders that substantially and negatively impact the patients' quality of life. Here, we review our current understanding on the pathophysiology of hepatic encephalopathy, irritable bowel syndrome, and diverticular disease, with a special focus on the gut microbiota composition associated with these disorders. Furthermore, we review the current clinical practice for their therapeutic treatments, including probiotics, diet change, non-adsorbable disaccharides, and antibiotics. We highlight that broad-spectrum non-adsorbable antibiotics, such as rifaximin, are quite effective and safe for the treatment of all essayed digestive diseases.

Fecal Microbiota Alterations Associated With Diarrhea-Predominant Irritable Bowel Syndrome

Altered gut microbiota are assumed to be involved in the pathogenesis of irritable bowel syndrome (IBS). However, gut microbiota alterations reported in different studies are divergent and sometimes even contradictory. To better elucidate the relationship between altered gut microbiota and IBS, we characterized fecal microbiota of diarrhea-predominant IBS (IBS-D) patients and further explored the effect of rifaximin on gut microbiota using bacterial 16S rRNA gene-targeted pyrosequencing. In our study, IBS-D patients defined by Rome III criteria and age-and-gender matched healthy controls (HC) were enrolled to investigate the fecal microbiota alterations. These IBS-D patients were then treated with rifaximin for 2 weeks and followed up for 10 weeks. Fecal microbiota alterations, small intestine bacterial overgrowth (SIBO) and gastrointestinal (GI) symptoms of IBS-D patients were analyzed before and after treatment. Our results showed fecal microbiota richness but not diversity was decreased in IBS-D patients as compared to HC and there were alterations of fecal microbiota at different taxonomy levels. The abundant phyla Firmicutes was significantly decreased and Bacteroidetes was increased in IBS-D patients. Moreover, the alterations of predominant fermenting bacteria such as Bacteroidales and Clostridiales might be involved in the pathophysiology of IBS-D. In addition, rifaximin was effective in terms of SIBO eradication and even GI symptoms of IBS-D patients achieved at least 10-week improvement after treatment. Furthermore, rifaximin induced alterations of some special bacteria rather than affected the overall composition of microbiota in IBS-D patients. Meanwhile, a potential decrease in propanoate and butanoate metabolism was found in these IBS-D patients after rifaximin treatment. Taken together, there were alterations of gut microbiota in IBS-D patients as compared to HC. Rifaximin could relieve GI symptoms, modify gut microbiota in IBS-D patients and eradicate SIBO in those patients with SIBO, suggesting an additional therapeutic mechanism of rifaximin in the treatment of IBS-D. Our findings of compositional gut microbiota alterations in IBS-D and the effect of rifaximin on the gut microbiota implied that altered gut microbiota were associated with the pathogenesis of IBS.

Fecal and Mucosa-Associated Intestinal Microbiota in Patients with Diarrhea-Predominant Irritable Bowel Syndrome

BACKGROUND

Irritable bowel syndrome (IBS) has been associated with changes in the intestinal microbiota. Only a few studies have explored differences in the mucosa-associated microbiota between IBS patients and healthy controls (HC).

AIMS

To characterize and compare the microbiota in mucosal and fecal samples from carefully selected patients with IBS-D and HC.

METHODS

The cohort was composed of 23 diarrhea-predominant IBS (IBS-D) patients and 24 HC. Fresh stool samples were collected from participants prior to the collection of colonic mucosal samples from an unprepped bowel. After DNA extraction, 16S rRNA genes were sequenced by 454 pyrosequencing and analyzed using the QIIME pipeline.

RESULTS

The fecal microbiota (luminal niche) of IBS-D patients was found to have reduced enteric richness compared to HC (P < 0.05), whereas no differences were observed between the two groups within the mucosal microbiota. Within the luminal niche, the relative proportions of Faecalibacterium genus were found to be lower in IBS-D than in HC and the Dorea genus was higher in IBS-D. None of the taxa proportions were significantly different in IBS-D patients versus HC using an FDR of ≤ 0.1 when analyzing samples that appeared in > 25% samples of either niche.

CONCLUSION

Fecal and mucosal microbiota of IBS-D patients and HC are very similar and are not sufficient to explain the reported altered physiology and symptomatology of IBS-D. Future studies should investigate intestinal microbiome-dependent functional activity in addition to the fecal and mucosal-associated microbial composition.