Review article: the antimicrobial effects of rifaximin on the gut microbiota

Exploring the Prevalence, Predictors, and Impact of Bacterial Infections to Guide Empiric Antimicrobial Decisions in Cirrhosis (EPIC-AD)

Background/Aims

This study delved into cirrhosis-related infections to unveil their epidemiology, risk factors, and implications for antimicrobial decisions.

Methods

We analyzed acutely decompensated cirrhosis patients (n = 971) from North India between 2013-2023 at a tertiary center. Microbiological and clinical features based on infection sites (EASL criteria) and patient outcomes were assessed.

Results

Median age was 45 years; 87% were males with 47% having alcoholic hepatitis. Of these, 675 (69.5%) had infections; 305 (45%) were culture-confirmed. Notably, 71% of confirmed cases were multi-drug resistant organisms (MDRO)-related, chiefly carbapenem-resistant (48%). MDRO prevalence was highest in pulmonary (80.5%) and skin-soft-tissue infections (76.5%). Site-specific distribution and antimicrobials were suggested. Predictive models identified prior hospitalization [OR:2.23 (CI:1.58-3.14)], norfloxacin prophylaxis [OR:2.26 (CI:1.44-3.55)], prior broad-spectrum antibiotic exposure [OR:1.61 (CI:1.12-2.30)], presence of systemic inflammatory response-SIRS [OR:1.75 (CI: 1.23-2.47)], procalcitonin [OR:4.64 (CI:3.36-6.40)], and HE grade [OR:1.41 (CI:1.04-1.90)], with an area under curve; AUC of 0.891 for infection prediction. For MDRO infection prediction, second infection [OR: 7.19 (CI: 4.11-12.56)], norfloxacin prophylaxis [OR: 2.76 (CI: 1.84-4.13)], CLIF-C OF [OR: 1.10 (CI: 1.01-1.20)], prior broad-spectrum antibiotic exposure [OR: 1.66 (CI: 1.07-2.55)], rifaximin [OR: 040 (0.22-0.74)] multisite [OR: 3.67 (CI: 1.07-12.56)], and polymicrobial infection [OR: 4.55 (CI: 1.45-14.17)] yielded an AUC of 0.779 and 93% specificity. Norfloxacin prophylaxis, multisite infection, mechanical ventilation, prior broad-spectrum antibiotic exposure, and infection as acute precipitant predicted carbapenem-resistant infection (AUC: 0.821). Infections (culture-proven or probable), MDROs, carbapenem/pan-drug resistance, and second infections independently linked with mortality (P < 0.001), adjusted for age, leucocytosis, and organ failures. A model incorporating age [HR:1.02 (CI: 1.01-1.03), infection [HR:1.52 (CI: 1.05-2.20)], prior hospitalization [HR:5.33 (CI: 3.75-7.57)], norfloxacin [HR:1.29 (CI: 1.01-1.65)], multisite infection [HR:1.47 (CI:1.06-2.04)], and chronic liver failure consortium-organ failure score; CLIF-C OF [HR:1.17 (CI: 1.11-1.23)] predicted mortality with C-statistics of 0.782 (P < 0.05).

Conclusion

High MDRO burden, especially carbapenem-resistant, necessitates urgent control measures in cirrhosis. Site-specific epidemiology and risk models can guide empirical antimicrobial choices in cirrhosis management.

The potential for development of clinically relevant microbial resistance to rifaximin-α: a narrative review

Rifaximin-α is a gut-targeted antibiotic indicated for numerous gastrointestinal and liver diseases. Its multifaceted mechanism of action goes beyond direct antimicrobial effects, including alterations in bacterial virulence, cytoprotective effects on host epithelial cells, improvement of impaired intestinal permeability, and reduction of proinflammatory cytokine expression via activation of the pregnane X receptor. Rifaximin-α is virtually non-absorbed, with low systemic drug levels contributing to its excellent safety profile. While there are high concentrations of drug in the colon, low water solubility leads to low colonic drug bioavailability, protecting the gut microbiome. Rifaximin-α appears to be more active in the bile-rich small bowel. Its important biologic effects are largely at sub-inhibitory concentration. Although in vitro testing of clinical isolates from rifaximin recipients has revealed rifaximin-resistant strains in some studies, the risk of emergent rifaximin-α resistance appears to be lower than for many other antibiotics. Rifaximin-α has been used for many years for traveler's diarrhea with no apparent increase in resistance levels in causative pathogens. Further, rifaximin-α retains its efficacy after long-term and recurrent usage in chronic gastrointestinal disorders. There are numerous reasons why the risk of microbial resistance to rifaximin-α may be lower than that for other agents, including low intestinal bioavailability in the aqueous colon, the mechanisms of action of rifaximin-α not requiring inhibitory concentrations of drug, and the low risk of cross transmission of rifaximin-α resistance between bacterial species. Reported emergence of vancomycin-resistant Enterococcus in liver-disease patients maintained on rifaximin needs to be actively studied. Further studies are required to assess the possible correlation between in vitro resistance and rifaximin-α efficacy.

Inflammatory bowel disease and Clostridium difficile infection: clinical presentation, diagnosis, and management

As a frequent complication of inflammatory bowel disease (IBD), Clostridium difficile infection (CDI) was confirmed to not only aggravate the symptoms of IBD but also result in unexpected outcomes, including death. With the increasing prevalence rate of IBD and the updating of CDI diagnosis, the incidence of CDI in IBD patients is also seen rising. Although a detection method consisting of glutamate dehydrogenase immunoassay or nucleic acid amplification test and then toxin A/B enzyme immunoassay was recommended and widely adopted, the diagnosis of CDI in IBD is still a challenge because of the overlap between the symptoms of CDI in IBD and CDI itself. Vancomycin and fidaxomicin are the first-line therapy for CDI in IBD; however, the treatment has different effects due to the complexity of IBD patients' conditions and the choice of different treatment schemes. Although the use of fecal microbial transplantation is now in the ascendant for IBD management, the prospects are still uncertain and the prevention and treatment of the recurrence of CDI in IBD remain a clinical challenge. In this paper, the epidemiology, pathophysiology, clinical manifestation, prevention, and therapy of CDI in IBD were summarized and presented.

Implications of anaemia and response to anaemia treatment on outcomes in patients with cirrhosis

Background & Aims

Anaemia is frequently observed in patients with cirrhosis and was identified as a predictor of adverse outcomes, such as increased mortality and occurrence of acute-on-chronic liver failure. To date, the possible effects of iron supplementation on these adverse outcomes are not well described. We therefore aimed to assess the role of iron supplementation in patients with cirrhosis and its capability to improve prognosis.

Methods

Laboratory diagnostics were performed in consecutive outpatients with cirrhosis admitted between July 2018 and December 2019 to the University Hospital Essen. Associations with transplant-free survival were assessed in regression models.

Results

A total of 317 outpatients with cirrhosis were included, of whom 61 received a liver transplant (n = 19) or died (n = 42). In multivariate Cox regression analysis, male sex (hazard ratio [HR] = 3.33, 95% CI [1.59, 6.99], p = 0.001), model for end-stage liver disease score (HR = 1.19, 95% CI [1.11, 1.27], p <0.001) and the increase of haemoglobin levels within 6 months (ΔHb6) (HR = 0.72, 95% CI [0.63, 0.83], p <0.001) were associated with transplant-free survival. Regarding the prediction of haemoglobin increase, intake of rifaximin (beta = 0.50, SD beta = 0.19, p = 0.007) and iron supplementation (beta = 0.79, SD beta = 0.26, p = 0.003) were significant predictors in multivariate analysis.

Conclusions

An increase of haemoglobin levels is associated with improvement of transplant-free survival in patients with cirrhosis. Because the prediction of haemoglobin increase significantly depends on rifaximin and iron supplementation, application of these two medications can have an important impact on the outcome of these patients.

Impact and implications

Anaemia is very common in patients with cirrhosis and is known to be a predictor of negative outcomes, but little is known about the effect of iron substitution in these individuals. In our cohort, increase of haemoglobin levels improved transplant-free survival of patients with cirrhosis. The increase of haemoglobin levels was mainly induced by iron supplementation and was even stronger in the case of concomitant use of iron and rifaximin.

Clinical trial registration

UME-ID-10042.

Modulation of duodenal and jejunal microbiota by rifaximin in mice with CCl4-induced liver fibrosis

BACKGROUND

Rifaximin is a poorly absorbed broad-spectrum antibiotic used for hepatic encephalopathy. Although increased Lactobacillaceae and decreased Bacteroidetes abundance are characteristic of hepatic encephalopathy, rifaximin does not dramatically alter the stool microbiota. As the antimicrobial effect of rifaximin increases by micellization with bile acids, we hypothesized that rifaximin alters the microbiota in the duodenum and jejunum, where the levels of bile acids are abundant.

METHODS AND RESULTS

Eight-week-old BALB/c mice were injected with carbon tetrachloride (CCl₄) intraperitoneally for 12 weeks to induce liver fibrosis. The mice were grouped into the control (n = 9), CCl₄ (n = 13), and rifaximin group in which mice were treated with rifaximin for two weeks after CCl₄ administration (n = 13). We analyzed the microbiota of the duodenum, jejunum, ileum, cecum, and stool using 16S ribosomal RNA gene analysis. The content of Lactobacillaceae, the most abundant bacterial family in the duodenum and small intestine, increased in the CCl₄ group, especially in the jejunum (median 67.0% vs 87.8%, p = 0.03). Rifaximin significantly decreased Lactobacillaceae content in the duodenum (median 79.4% vs 19.0%, p = 0.006) and jejunum (median 87.8% vs 61.3%, p = 0.03), but not in the ileum, cecum, and stool. Bacteroidetes abundance tended to decrease on CCl₄ administration and increased following rifaximin treatment in the duodenum and jejunum. S24_7, the most abundant family in Bacteroidetes, demonstrated a significant inverse correlation with Lactobacillaceae (duodenum, r = - 0.61, p < 0.001; jejunum, r = - 0.72, p < 0.001). In the ileum, cecum, and stool, the effect of rifaximin on the microbiota was minimal, with changes within the same phylum. The percentage of bacterial families, such as Lactobacillaceae and S24_7 in the duodenum and small intestine, did not correlate with that in the stool.

CONCLUSIONS

The abundance of Lactobacillaceae increased in the jejunum of mice with CCl₄-induced liver fibrosis, while rifaximin significantly reduced it in the duodenum and jejunum. Thus, rifaximin possibly exerts its effect by altering the duodenal and jejunal microbiota. Furthermore, changes in the duodenal and small intestinal microbiota were not associated with that of stool, suggesting that the analysis of stool microbiota is insufficient to evaluate upper intestinal microbiota.

Diverticular Disease and Rifaximin: An Evidence-Based Review

There have been considerable advances in the treatment of diverticular disease in recent years. Antibiotics are frequently used to treat symptoms and prevent complications. Rifaximin, a non-absorbable antibiotic, is a common therapeutic choice for symptomatic diverticular disease in various countries, including Italy. Because of its low systemic absorption and high concentration in stools, it is an excellent medicine for targeting the gastrointestinal tract, where it has a beneficial effect in addition to its antibacterial properties. Current evidence shows that cyclical rifaximin usage in conjunction with a high-fiber diet is safe and effective for treating symptomatic uncomplicated diverticular disease, while the cost-effectiveness of long-term treatment is unknown. The use of rifaximin to prevent recurrent diverticulitis is promising, but further studies are needed to confirm its therapeutic benefit. Unfortunately, there is no available evidence on the efficacy of rifaximin treatment for acute uncomplicated diverticulitis.

Improving Management of Portal Hypertension: The Potential Benefit of Non-Etiological Therapies in Cirrhosis

Portal hypertension is the consequence of cirrhosis and results from increased sinusoidal vascular resistance and hepatic blood inflow. Etiological therapies represent the first intervention to prevent a significant increase in portal pressure due to chronic liver damage. However, other superimposed pathophysiological drivers may worsen liver disease, including inflammation, bacterial translocation, endothelial dysfunction, and hyperactivation of hemostasis. These mechanisms can be targeted by a specific class of drugs already used in clinical practice. Albumin, rifaximin, statins, aspirin, and anticoagulants have been tested in cirrhosis and were a topic of discussion in the last Baveno consensus as non-etiological therapies. Based on the pathogenesis of portal hypertension in cirrhosis, our review summarizes the main mechanisms targeted by these drugs as well as the clinical evidence that considers them a valid complementary option to manage patients with cirrhosis and portal hypertension.

Progress in research of low-grade inflammation in irritable bowel syndrome

Irritable bowel syndrome (IBS) is a common intestinal disease with a prevalence of 10%-15%. However, its pathophysiology is still not completely clear, and it has long been considered as a functional disease. In recent years, it has been found that low-grade inflammation plays a pathogenic role in IBS. Studies have confirmed that there is persistent mucosal inflammation at the microscopic and molecular levels. This review discusses the evidence, role, and clinical relevance of mucosal inflammation in IBS. In addition to mucosal inflammation, neuroinflammation may lead to changes in neuroendocrine pathways and glucocorticoid receptor genes through the "gut-brain" axis, and thus cause IBS through proinflammatory phenotype and hypothalamic pituitary adrenal axis and 5-hydroxytryptamine dysfunction. The observation that IBS patients can benefit from anti-inflammatory therapy also confirms that IBS is associated with inflammation.

Effectiveness and Safety of Rifaximin-Containing Regimens for Helicobacter pylori Eradication: Systematic Review - Are They Potential Eradication Regimens?

Background

Rifaximin, a rifamycin antibiotic, is widely used to treat infectious diarrhea but not commonly used in H. pylori eradication. With its potential advantages of the agent, some studies were conducted on this topic. The aim of this study is to assess effectiveness and safety of rifaximin-containing regimens and to evaluate whether they are alternative choices for H. pylori eradication.

Methods

Scientific databases including PubMed, EMbase and Cochrane Library were used to identify clinical trials on rifaximin-containing regimens published from January 2000 to October 2021. Review Manager 5.4 and STATA12 were adopted for the systematic review.

Results

In this study, totally 1025 patients were included from 3 randomized controlled and 9 single-arm studies. It showed that the differences in effectiveness and safety between rifaximin-containing and first-line regimens were not statistically significant in randomized controlled trials. However, the results of the single-arm trials indicated that the eradication and adverse drug reaction rate varied suggesting data instability (r=38.1%-85.4%, r_ADR 0.00–67.5% by ITT analysis). Among them, the eradication rate of pediatric patients (r=85.4% by ITT analysis) was higher than that of adult patients (r=38.1–74.5% by ITT analysis). Meanwhile, in all adult subgroups (triple or quadruple, with or without amoxicillin, different duration and rifaximin dose), the results did not show sufficient effectiveness as all the eradication rates did not meet the minimum ideal or ideal target.

Conclusion

Taken together, rifaximin-containing regimens should not be recommended for H. pylori eradication as they cannot achieve the eradication rate desired.

Rifaximin Protects against Malathion-Induced Rat Testicular Toxicity: A Possible Clue on Modulating Gut Microbiome and Inhibition of Oxidative Stress by Mitophagy

Testicular dysfunction is caused by chronic exposure to environmental pollution, such as malathion, which causes oxidative stress, promoting cell damage. Autophagy is a key cellular process for eliminating malfunctioning organelles, such as the mitochondria (mitophagy), an eminent source of reactive oxygen species (ROS). Autophagy is crucial for protection against testicular damage. Rifaximin (RFX) is a non-absorbable antibiotic that can reshape the gut microbiome, making it effective in different gastrointestinal disorders. Interestingly, the gut microbiome produces short chain fatty acids (SCFAs) in the circulation, which act as signal molecules to regulate the autophagy. In this study, we investigated the regulatory effects of RFX on gut microbiota and its circulating metabolites SCFA and linked them with the autophagy in testicular tissues in response to malathion administration. Moreover, we divided the groups of rats that used malathion and RFX into a two-week group to investigate the mitophagy process and a four-week group to study mitochondriogenesis. The current study revealed that after two weeks of cotreatment with RFX, apoptosis was inhibited, oxidative stress was improved, and autophagy was induced. More specifically, PINK1 was overexpressed, identifying mitophagy activation. After four weeks of cotreatment with RFX, there was an increase in acetate and propionate-producing microflora, as well as the circulating levels of SCFAs. In accordance with this, the expression of PGC-1α, a downstream to SCFAs action on their receptors, was activated. PGC-1α is an upstream activator of mitophagy and mitochondriogenesis. In this sense, the protein expression of TFAM, which regulates the mitochondrial genome, was upregulated along with a significant decrease in apoptosis and oxidative stress. Conclusion: we found that RFX has a positive regulatory effect on mitophagy and mitochondria biogenesis, which could explain the novel role played by RFX in preventing the adverse effects of malathion on testicular tissue.

Hepatic encephalopathy

Hepatic encephalopathy (HE) is a prognostically relevant neuropsychiatric syndrome that occurs in the course of acute or chronic liver disease. Besides ascites and variceal bleeding, it is the most serious complication of decompensated liver cirrhosis. Ammonia and inflammation are major triggers for the appearance of HE, which in patients with liver cirrhosis involves pathophysiologically low-grade cerebral oedema with oxidative/nitrosative stress, inflammation and disturbances of oscillatory networks in the brain. Severity classification and diagnostic approaches regarding mild forms of HE are still a matter of debate. Current medical treatment predominantly involves lactulose and rifaximin following rigorous treatment of so-called known HE precipitating factors. New treatments based on an improved pathophysiological understanding are emerging.

The Use of Rifaximin in Patients With Cirrhosis

Rifaximin is an oral nonsystemic antibiotic with minimal gastrointestinal absorption and broad-spectrum antibacterial activity covering both gram-positive and gram-negative organisms. Rifaximin is currently used worldwide in patients with cirrhosis for preventing recurrent HE because its efficacy and safety have been proven by large randomized clinical trials. In the last decade, experimental and clinical evidence suggest that rifaximin could have other beneficial effects on the course of cirrhosis by modulating the gut microbiome and affecting the gut-liver axis, which in turn can interfere with major events of the pathophysiological cascade underlying decompensated cirrhosis, such as systemic inflammatory syndrome, portal hypertension, and bacterial infections. However, the use of rifaximin for prevention or treatment of other complications, including spontaneous bacterial peritonitis or other bacterial infections, is not accepted because evidence by clinical trials is still very weak. The present review deals in the first part with the potential impact of rifaximin on pathogenic mechanisms in liver diseases, whereas in the second part, its clinical effects are critically discussed. It clearly emerges that, because of its potential activity on multiple pathogenic events, the efficacy of rifaximin in the prevention or management of complications other than HE deserves to be investigated extensively. The results of double-blinded, adequately powered randomized clinical trials assessing the effect of rifaximin, alone or in combination with other drugs, on hard clinical endpoints, such as decompensation of cirrhosis, acute-on-chronic liver failure, and mortality, are therefore eagerly awaited.

Add-on interventions for the prevention of recurrent Clostridioides Difficile infection: A systematic review and network meta-analysis

OBJECTIVES

We aimed to assess the comparative efficacy and safety of adjunctive interventions for the prevention of Clostridioides difficile recurrence.

METHODS

We searched Medline, Embase, CENTRAL, and clinicaltrials.gov up to May 2021. We included randomized controlled trials comparing interventions added to antibiotic therapy for prevention of CDI recurrence, to placebo or each other. Efficacy outcomes were CDI and diarrhea recurrence. Safety outcomes included the incidence of any adverse event (AE), serious AEs, and discontinuation due to AEs. We performed random-effects network meta-analysis. We ranked interventions based on SUCRA (surface under the cumulative ranking curve) probabilities. We assessed confidence in estimates utilizing the CINeMA (Confidence in Network Meta-Analysis) framework.

RESULTS

Fifteen trials (3909 patients) assessed 9 interventions. Oligofructose (OR 0.17; 95% CI, 0.07 to 0.46), NTCD-M3 (OR 0.29; 95% CI, 0.12 to 0.68), rifaximin (OR 0.47; 95% CI, 0.24 to 0.93), RBX2660 (OR 0.47; 95% CI, 0.22 to 0.99), the combination bezlotoxumab/actoxumab (OR 0.47; 95% CI, 0.37 to 0.60), and bezlotoxumab (OR, 0.53; 95% CI, 0.42 to 0.68) were associated with lower incidence of CDI recurrence than placebo (moderate confidence). Oligofructose was ranked highest, however data for oligofructose were derived solely from one small trial. Probiotics, actoxumab and SER-109 were not superior to placebo (low confidence). Probiotics were not well tolerated (low confidence) and actoxumab showed high rates of serious AEs (moderate confidence).

CONCLUSION

Add-on treatment with oligofructose, NTCD-M3 spores, rifaximin, RBX2660, and bezlotoxumab likely reduces the risk of CDI. Evidence on probiotics and SER-109 are uncertain, thus adequately powered trials are warranted.

Antibiotics to modify sickle cell disease vaso-occlusive crisis?

Despite the availability of hydroxyurea, the clinical use of the medication among patients with sickle cell disease (SCD) remains low in the United States. Given the high healthcare utilization cost, SCD requires new therapeutic approaches. Recent studies demonstrated bacterial overgrowth and dysbiosis-related intestinal pathophysiological changes in SCD. Intestinal microbes regulate neutrophil ageing. Aged and activated neutrophils contribute to the pathogenesis of vaso-occlusive crisis (VOC) in SCD. In this paper, we will review the pre-clinical and clinical data on how antibiotics might reduce the intestinal microbial density and influence the course of VOC. Based on these observations, we will discuss rationales for and potential challenges to antibiotic-based therapeutic approaches that may modify the clinical course of VOC in SCD.

Management of bacterial and fungal infections in cirrhosis: The MDRO challenge

Bacterial infections are frequent in cirrhotic patients with acute decompensation or acute-on-chronic liver failure and can complicate the clinical course. Delayed diagnosis and inappropriate empirical treatments are associated with poor prognosis and increased mortality. Fungal infections are much less frequent, usually nosocomial and associated with extremely high short-term mortality. Early diagnosis and adequate empirical treatment of infections is therefore key in the management of these patients. In recent decades, antibiotic resistance has become a major worldwide problem in patients with cirrhosis, warranting a more complex approach to antibiotic treatment that includes the use of broad-spectrum antibiotics, new administration strategies, novel drugs and de-escalation policies. Herein, we review epidemiological changes, the main types of multidrug-resistant organisms, mechanisms of resistance, new rapid diagnostic tools and currently available therapeutic options for bacterial and fungal infections in cirrhosis.

PK/PD Modeling to Assess Rifaximin Clinical Dosage in a Mouse Model of Staphylococcus aureus-Induced Mastitis

Staphylococcus aureus (S. aureus) is a common pathogen that causes mastitis, an infection of the milk-secreting tissue of the udder, in dairy cows, and presents a huge economic problem for the dairy industry worldwide. Thus, control and treatment of mastitis in dairy cows is vital in order to reduce the costs associated with the disease. The main purpose of the current work was to examine the current dosage of rifaximin for the treatment mastitis in cows caused by S. aureus using pharmacokinetic/pharmacodynamic integration in a mouse mastitis model. The mouse mastitis model was established via injection of S. aureus Newbould 305 (400 CFU/gland) into the mouse mammary gland. A single dose of 50, 100, 200, or 400 μg/gland, administered via intramammary infusion, was used to study the pharmacokinetics of rifaximin. The pharmacokinetic parameters were analyzed by non-compartment and non-linear mixed-effect models using Phoenix software (version 8.1; Pharsight, USA). In vivo pharmacodynamics was used to examine 18 therapeutic regimens covering various doses ranging from 25 to 800 μg/gland and three dosing intervals of 8, 12, and 24 h per 24 h experiment cycle. The antibacterial effect of rifaximin was elevated with higher concentrations of rifaximin or shorter intervals of administration. The percentage of time that drug concentrations exceeded the MIC during a dose interval (%T > MIC) was generally 100% for rifaximin and was not better than AUC₂₄/MIC in the sigmoid E_max model of inhibitory effect. The optimal antibacterial effect was 2log₁₀CFU/gland when the magnitude of AUC₂₄/MIC reached 14,281.63 h. A total of 14,281.63 h of AUC₂₄/MIC was defined as a target value in the Monte Carlo simulation. The clinically recommended dosage regimen of 100 mg/gland every 8 h in 1 day achieved an 82.97% cure rate for the treatment of bovine mastitis caused by Staphylococcus aureus infection.

A contemporary review of Clostridioides difficile infections in patients with haematologic diseases

Clostridioides (Clostridium) difficile (C. difficile) infection is one of the most common causes of increased morbidity and mortality. Approximately 500 000 C. difficile infections (CDIs) occur each year in the United States, and they result in more than 29 000 deaths. Patients with haematologic diseases are at a higher risk for this infection due to frequent hospitalization and exposure to treatment-associated risk factors. Whilst several currently available antimicrobial agents offer resolution, recurrence of infection remains a major concern. Recent advancement in deciphering C. difficile virulence mechanisms and identification of its allies in contributing to the infection has led to the development of alternative treatment strategies. Here, we will provide a contemporary discussion of how major risk factors in haematologic diseases, such as immunosuppression, chemoradiation, use of antibiotic, proton pump inhibitor and opioid, and deficiency in butyrate and antimicrobial peptides contribute to C. difficile infection. Next, we will highlight different approaches to control and mitigate this infection such as antibiotic stewardship and faecal microbiota transplantation. Finally, we will explore several emerging treatments such as use of pre- and probiotics, immunotherapy and microbiome-sparing agents.

Clinical and Genetic Tumor Characteristics of Responding and Non-Responding Patients to PD-1 Inhibition in Hepatocellular Carcinoma

Immune checkpoint inhibitors (ICIs) belong to the therapeutic armamentarium in advanced hepatocellular carcinoma (HCC). However, only a minority of patients benefit from immunotherapy. Therefore, we aimed to identify indicators of therapy response. This multicenter analysis included 99 HCC patients. Progression-free (PFS) and overall survival (OS) were studied by Kaplan-Meier analyses for clinical parameters using weighted log-rank testing. Next-generation sequencing (NGS) was performed in a subset of 15 patients. The objective response (OR) rate was 19% median OS (mOS)16.7 months. Forty-one percent reached a PFS > 6 months; these patients had a significantly longer mOS (32.0 vs. 8.5 months). Child-Pugh (CP) A and B patients showed a mOS of 22.1 and 12.1 months, respectively. Ten of thirty CP-B patients reached PFS > 6 months, including 3 patients with an OR. Tumor mutational burden (TMB) could not predict responders. Of note, antibiotic treatment within 30 days around ICI initiation was associated with significantly shorter mOS (8.5 vs. 17.4 months). Taken together, this study shows favorable outcomes for OS with low AFP, OR, and PFS > 6 months. No specific genetic pattern, including TMB, could identify responders. Antibiotics around treatment initiation were associated with worse outcome, suggesting an influence of the host microbiome on therapy success.

Regulating Intestinal Microbiota in the Prevention and Treatment of Alcohol-Related Liver Disease

When alcohol-related liver disease occurs, the number and composition ratio of intestinal microorganisms will accordingly change. The alcohol-induced changes in the intestinal microbiota play a pivotal role in the process of developing the alcohol-related liver disease through the translocation of microbial products due to increased intestinal permeability. In recent years, therapeutic interventions with a concentration on regulating intestinal microbiota have been conducted for patients with alcohol-related liver disease. We aimed to provide a critical review and updates on the prevention and treatment of alcohol-related liver disease through regulating intestinal microbiota. A literature search was performed on the PubMed database for studies published in English about the therapeutic intervention with microbiota using animal models and patients with alcohol-related liver disease (1/2010-4/2020). The accumulating pieces of evidence suggest that the therapeutic use of probiotics, prebiotics, antibiotics, phages, or fecal microbial transplantation may have several influences on alcohol-related liver disease patients. Emergent data unveiled that these interventions can further regulate the composition of intestinal microbiota, minimize the negative impact of microbiota on the liver, and prevent disease progression from mild to severe alcoholic hepatitis, fibrosis, cirrhosis, or even liver cancer. The current review provides updates on the advances of therapeutic interventions with the effects of regulating intestinal microbiota on patients who have alcohol-related liver disease. In addition, the data gaps and research directions on further exploration of the role of intestinal microbiota for the management of the alcohol-related liver disease are also discussed.

Hepatic encephalopathy: Novel insights into classification, pathophysiology and therapy

Hepatic encephalopathy (HE) is a frequent and serious complication of both chronic liver disease and acute liver failure. HE manifests as a wide spectrum of neuropsychiatric abnormalities, from subclinical changes (mild cognitive impairment) to marked disorientation, confusion and coma. The clinical and economic burden of HE is considerable, and it contributes greatly to impaired quality of life, morbidity and mortality. This review will critically discuss the latest classification of HE, as well as the pathogenesis and pathophysiological pathways underlying the neurological decline in patients with end-stage liver disease. In addition, management strategies, diagnostic approaches, currently available therapeutic options and novel treatment strategies are discussed.

Gut Microbiota-Derived Propionate Regulates the Expression of Reg3 Mucosal Lectins and Ameliorates Experimental Colitis in Mice

BACKGROUND AND AIMS

Regenerating islet-derived protein type 3 [Reg3] lectins are antimicrobial peptides at mucosal surfaces of the gut, whose expression is regulated by pathogenic gut microbes via interleukin-22- or Toll-like receptor signalling. In addition to antimicrobial effects, tissue protection is hypothesized, but has been poorly investigated in the gut.

METHODS

We applied antibiotic-induced microbiota perturbations, gnotobiotic approaches and a dextran-sodium sulfate [DSS] colitis model to assess microbial Reg3 regulation in the intestines and its role in colitis. We also used an intestinal organoid model to investigate this axis in vitro.

RESULTS

First, we studied whether gut commensals are involved in Reg3 expression in mice, and found that antibiotic-mediated reduction of Clostridia downregulated intestinal Reg3B. A loss in Clostridia was accompanied by a significant reduction of short-chain fatty acids [SCFAs], and knock-out [KO] mice for SCFA receptors GPR43 and GPR109 expressed less intestinal Reg3B/-G. Propionate was found to induce Reg3 in intestinal organoids and in gnotobiotic mice colonized with a defined, SCFA-producing microbiota. Investigating the role of Reg3B as a protective factor in colitis, we found that Reg3B-KO mice display increased inflammation and less crypt proliferation in the DSS colitis model. Propionate decreased colitis and increased proliferation. Treatment of organoids exposed to DSS with Reg3B or propionate reversed the chemical injury with a loss of expression of the stem-cell marker Lgr5 and Olfm4.

CONCLUSIONS

Our results suggest that Clostridia can regulate Reg3-associated epithelial homeostasis through propionate signalling. We also provide evidence that the Reg3-propionate axis may be an important mediator of gut epithelial regeneration in colitis.

A Significant Question in Cancer Risk and Therapy: Are Antibiotics Positive or Negative Effectors? Current Answers and Possible Alternatives

Cancer is predominantly considered as an environmental disease caused by genetic or epigenetic alterations induced by exposure to extrinsic (e.g., carcinogens, pollutants, radiation) or intrinsic (e.g., metabolic, immune or genetic deficiencies). Over-exposure to antibiotics, which is favored by unregulated access as well as inappropriate prescriptions by physicians, is known to have led to serious health problems such as the rise of antibiotic resistance, in particular in poorly developed countries. In this review, the attention is focused on evaluating the effects of antibiotic exposure on cancer risk and on the outcome of cancer therapeutic protocols, either directly acting as extrinsic promoters, or indirectly, through interactions with the human gut microbiota. The preponderant evidence derived from information reported over the last 10 years confirms that antibiotic exposure tends to increase cancer risk and, unfortunately, that it reduces the efficacy of various forms of cancer therapy (e.g., chemo-, radio-, and immunotherapy alone or in combination). Alternatives to the current patterns of antibiotic use, such as introducing new antibiotics, bacteriophages or enzybiotics, and implementing dysbiosis-reducing microbiota modulatory strategies in oncology, are discussed. The information is in the end considered from the perspective of the most recent findings on the tumor-specific and intracellular location of the tumor microbiota, and of the most recent theories proposed to explain cancer etiology on the notion of regression of the eukaryotic cells and systems to stages characterized for a lack of coordination among their components of prokaryotic origin, which is promoted by injuries caused by environmental insults.

Detrimental Effect of Broad-spectrum Antibiotics on Intestinal Microbiome Diversity in Patients After Allogeneic Stem Cell Transplantation: Lack of Commensal Sparing Antibiotics

BACKGROUND

Maintaining gastrointestinal (GI) microbiome diversity plays a key role during allogeneic stem cell transplantation (ASCT), and loss of diversity correlates with acute GI graft versus host disease (GvHD) and poor outcomes.

METHODS

In this retrospective analysis of 161 ASCT patients, we used serial analyses of urinary 3-indoxyl sulfate (3-IS) levels and GI microbiome parameters within the first 10 days after ASCT to identify potential commensal microbiota-sparing antibiotics. Based on antibiotic activity, we formed 3 subgroups (Rifaximin without systemic antibiotics, Rifaximin with systemic antibiotics, and Ciprofloxacin/Metronidazole with/without systemic antibiotics).

RESULTS

Mono-antibiosis with Rifaximin revealed higher 3-IS levels (P < .001), higher Clostridium cluster XIVa (CCXIVa) abundance (P = .004), and higher Shannon indices (P = .01) compared to Ciprofloxacin/Metronidazole with/without systemic antibiotics. Rifaximin followed by systemic antibiotics maintained microbiome diversity compared to Ciprofloxacin/Metronidazole with/without systemic antibiotics, as these patients showed still higher 3-IS levels (P = .04), higher CCXIVa copy numbers (P = .01), and higher Shannon indexes (P = .01). Even for this larger cohort of patients, the outcome was superior with regard to GI GvHD (P = .05) and lower transplant-related mortality (P < .001) for patients receiving Rifaximin plus systemic antibiotics compared to other types of systemic antibiotic treatment. Antibiosis with Ciprofloxacin/Metronidazole (n = 12, P = .01), Piperacillin/Tazobactam (n = 52, P = .01), Meropenem/Vancomycin (n = 16, P = .003), Ceftazidime (n = 10, P = .03), or multiple systemic antibiotics (n = 53, P = .001) showed significantly lower 3-IS levels compared to mono-antibiosis with Rifaximin (n = 14) or intravenous Vancomycin (n = 4, not statistically significant).

CONCLUSIONS

Different types of antibiotic treatments show different impacts on markers of microbiome diversity. The identification of antibiotics sparing commensal bacteria remains an ongoing challenge. However, Rifaximin allowed a higher intestinal microbiome diversity, even in the presence of systemic broad-spectrum antibiotics.

Fecal bacteria can predict the efficacy of rifaximin in patients with diarrhea-predominant irritable bowel syndrome

OBJECTIVE

Rifaximin for treating diarrhea-predominant irritable bowel syndrome (IBS-D) by regulating intestinal microbiota has been studied and recommended. In this study, we tried to investigate the effect of rifaximin on different components of intestinal microbiota and explore which component of gut microbiota can predict the efficacy of rifaximin in IBS-D.

METHODS

Healthy controls (HC) and IBS-D patients meeting the Rome III criteria were recruited, and IBS-D patients were orally administered 400 mg rifaximin three times daily for 2 weeks. Subjects were tested for small intestinal bacterial overgrowth (SIBO), their symptoms were recorded, and fecal and rectal mucosal samples were collected before and after treatment. Fecal and rectal mucosal bacterial data were obtained via 16S rRNA sequencing, and fecal fungal data were obtained via ITS2 sequencing.

RESULTS

IBS-D patients were divided into two subgroups based on fecal bacterial composition, IBS1 (patients whose fecal bacterial composition were different from HC) and IBS0 (patients whose fecal bacterial profiles were similar to HC). Rifaximin increased fecal Bifidobacterium and decreased E. coli and Enterobacter in IBS1 patients. Although rectal mucosal bacteria and fecal fungi were not significantly altered in all patients after rifaximin intervention, rifaximin enhanced the connections among fecal bacteria, mucosal bacteria and fecal fungi in IBS1 patients. Compared with IBS0, we surprisingly found rifaximin ameliorated abdominal symptoms of IBS1 much better. Receiver operating curve analysis revealed patients whose fecal microbial dysbiosis indices (MDI) were higher than -3.006 could be diagnosed as IBS1.

CONCLUSION

Fecal bacterial dysbiosis could be a biomarker for rifaximin treatment for IBS-D.

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.

HS-SPME-GC-MS approach for the analysis of volatile salivary metabolites and application in a case study for the indirect assessment of gut microbiota

In this work, a straightforward analytical approach based on headspace solid-phase microextraction coupled with gas chromatography-mass spectrometry was developed for the analysis of salivary volatile organic compounds without any prior derivatization step. With a sample volume of 500 μL, optimal conditions were achieved by allowing the sample to equilibrate for 10 min at 50 °C and then extracting the samples for 10 min at the same temperature, using a carboxen/polydimethylsiloxane fibre. The method allowed the simultaneous identification and quantification of 20 compounds in sample headspace, including short-chain fatty acids and their derivatives which are commonly analysed after analyte derivatization. The proof of applicability of the methodology was performed with a case study regarding the analysis of the dynamics of volatile metabolites in saliva of a single subject undergoing 5-day treatment with rifaximin antibiotic. Non-stimulated saliva samples were collected over 3 weeks from a nominally healthy volunteer before, during, and after antibiotic treatment. The variations of some metabolites, known to be produced by the microbiota and by bacteria that are susceptible to antibiotics, suggest that the study of the dynamics of salivary metabolites can be an excellent indirect method for analysing the gut microbiota. This approach is novel from an analytical standpoint, and it encourages further studies combining saliva metabolite profiles and gut microbiota dynamics. Graphical abstract.

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.

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.

Effects of Psychological, Environmental and Physical Stressors on the Gut Microbiota

Stress, a ubiquitous part of daily human life, has varied biological effects which are increasingly recognized as including modulation of commensal microorganisms residing in the gastrointestinal tract, the gut microbiota. In turn, the gut microbiota influences the host stress response and associated sequelae, thereby implicating the gut microbiota as an important mediator of host health. This narrative review aims to summarize evidence concerning the impact of psychological, environmental, and physical stressors on gut microbiota composition and function. The stressors reviewed include psychological stress, circadian disruption, sleep deprivation, environmental extremes (high altitude, heat, and cold), environmental pathogens, toxicants, pollutants, and noise, physical activity, and diet (nutrient composition and food restriction). Stressors were selected for their direct relevance to military personnel, a population that is commonly exposed to these stressors, often at extremes, and in combination. However, the selected stressors are also common, alone or in combination, in some civilian populations. Evidence from preclinical studies collectively indicates that the reviewed stressors alter the composition, function and metabolic activity of the gut microbiota, but that effects vary across stressors, and can include effects that may be beneficial or detrimental to host health. Translation of these findings to humans is largely lacking at present. This gap precludes concluding with certainty that transient or cumulative exposures to psychological, environmental, and physical stressors have any consistent, meaningful impact on the human gut microbiota. However, provocative preclinical evidence highlights a need for translational research aiming to elucidate the impact of stressors on the human gut microbiota, and how the gut microbiota can be manipulated, for example by using nutrition, to mitigate adverse stress responses.

Differences in the digestive enzyme activity, intestinal mucosa and microbial community in loach cultivated in two separate environments

BACKGROUND

Fish culture in rice paddies can contribute to increasing yields of rice and surplus fish products. Environmental impacts and food-safety issues have become important topics in aquaculture, and organic foods currently were paid attention by researchers and industry practitioners. But the mechanism of differences in quality of Loach (Paramisgurnus dabryanus) reared in rice fields and ponds remains largely uncharacterized. In this study,digestive enzyme activity, intestinal mucosa cells and the gut microbial community of loach were determined under the two separate cultivation modes.

RESULTS

The levels of intestinal digestive enzyme activity of fish reared in the paddy-cultivated mode (PACM) were higher (P < 0.05) than those in the pond-cultivated mode (POCM). It was extremely significant (P < 0.01) for the activity of lipase in the liver, foregut and midgut, and for the activities of amylase and trypsin in the hindgut. Acid mucous cells in the loach foregut in PACM were fewer than in POCM (P < 0.01). In summer, the abundance of the Firmicutes, Lactobacillus spp., Aeromonas hydrophila, Enterobacteriaceae and Streptococcus spp. in loach intestinal mucosa in PACM was higher than in POCM. In fall, the abundance of total bacteria, the Bacteroidetes, Bifidobacterium and Enterobacteriaceae in the intestinal mucosa in PACM was likewise higher than in POCM. These differences were significant (P < 0.05 or P < 0.01) between loach in the two separate culture modes for all microorganisms except for A. hydrophila and Streptococcus spp. In addition, quantitative PCR assays showed that some microorganisms presented consistently similar abundances in the gut as in the culture water.

CONCLUSIONS

These results showed some enzymatic activities involved in digestion in liver and intestine of loach in PACM were higher than those in POCM, as using digestive enzyme analysis and histological observation of intestinal sections. These findings suggest most of the microorganisms examined in the gut mucosa of loach in the two culture modes significantly differed in abundance between summer and fall. However, some pathogenic bacteria in the gut, particularly A. hydrophila, presented lower abundance in PACM in fall, yet did not differ in abundance between loach in the two cultivation modes.

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.

Rifaximin anti-inflammatory activity on bovine endometrium primary cell cultures: a preliminary study

Rifaximin is an unabsorbed oral antibiotic showing anti‐inflammatory properties in human pathologies like irritable bowel syndrome and inflammatory bowel disease. In veterinary medicine, rifaximin is primarily used in the treatment of dermatological diseases in all animal species, in therapy and prophylaxis of mastitis in cows and in the treatment of endometritis in cattle and horses. The aim of this preliminary study was to evaluate the anti‐inflammatory properties of rifaximin on primary cell cultures from bovine endometrium in which inflammatory response was induced by Lipopolysaccaride (LPS) treatment. Epithelial and stromal cells were isolated from bovine endometrium and separately incubated for 24 h with 1 μg mL⁻¹LPS after rifaximin (10, 50 and 100 μmol L⁻¹) or dexamethasone (10 μmol L⁻¹) pre‐treatment for 24 h. Supernatants were collected 24 h after LPS treatment and interleukin (IL)‐6 and IL‐8 accumulation was measured by ELISA. Rifaximin (10, 50 and 100 μmol L⁻¹) dose dependently inhibited the LPS‐induced increase in IL‐6 and IL‐8 in stromal cells, whereas in epithelial cells it was not possible to detect any accumulation of these interleukins. Rifaximin reduced IL‐6 and IL‐8 production, showing a potential anti‐inflammatory effect that opens up to new possibilities for the use of this drug in uterine inflammatory diseases.

Increased Pancreatic Protease Activity in Response to Antibiotics Impairs Gut Barrier and Triggers Colitis

Background & Aims

Antibiotic (ABx) therapy is associated with increased risk for Crohn's disease but underlying mechanisms are unknown. We observed high fecal serine protease activity (PA) to be a frequent side effect of ABx therapy. The aim of the present study was to unravel whether this rise in large intestinal PA may promote colitis development via detrimental effects on the large intestinal barrier.

Methods

Transwell experiments were used to assess the impact of high PA in ABx-treated patients or vancomycin/metronidazole-treated mice on the epithelial barrier. Serine protease profiling was performed using liquid chromatography-mass spectrometry/mass spectrometry analysis. The impact of high large intestinal PA on the intestinal barrier in wild-type and interleukin (IL)10-/- mice and on colitis development in IL10-/- mice was investigated using vancomycin/metronidazole with or without oral serine protease inhibitor (AEBSF) treatment.

Results

The ABx-induced, high large intestinal PA was caused by significantly increased levels of pancreatic proteases and impaired epithelial barrier integrity. In wild-type mice, the rise in PA caused a transient increase in intestinal permeability but did not affect susceptibility to chemically induced acute colitis. In IL10-/- mice, increased PA caused a consistent impairment of the intestinal barrier associated with inflammatory activation in the large intestinal tissue. In the long term, the vancomycin/metronidazole-induced lasting increase in PA aggravated colitis development in IL10-/- mice.

Conclusions

High large intestinal PA is a frequent adverse effect of ABx therapy, which is detrimental to the large intestinal barrier and may contribute to the development of chronic intestinal inflammation in susceptible individuals.

Antifibrotic and molecular aspects of rifaximin in alcoholic liver disease: study protocol for a randomized controlled trial

Background

Alcoholic liver disease is the leading cause of cirrhosis worldwide. Due to an increase in alcohol overuse, alcoholic liver disease has become an increased burden on health care systems. Abstinence from alcohol remains the cornerstone of alcoholic liver disease treatment; however, this approach is hampered by frequent relapse and lack of specific therapy for treating advanced cases of liver disease. In the present study, we hypothesized that gut microbiota drive the development of liver fibrosis and that modulation of gut microbiota with the gut-selective, nonabsorbable antibiotic rifaximin attenuates alcoholic liver fibrosis.

Methods/design

Our double-blind, placebo-controlled trial will include 136 participants with biopsy-verified alcoholic fibrosis (Ishak liver fibrosis score of 1–4). Participants are randomized 1:1 to receive placebo or 550 mg of rifaximin twice daily for 18 months. A liver biopsy will be performed at the end of the treatment period to evaluate the effect of drug treatment on liver fibrosis. Stool, urine, and saliva specimens will be collected before treatment begins, at 1 month, and at the end of the treatment period. Fecal samples are used for microbiome deep sequencing. Changes in microbiome composition are compared before and after the trial medication period and linked to changes in liver fibrosis.

Discussion

This is the first clinical trial to evaluate the effect of gut microbiota on liver fibrosis in humans. If gut microbiota are an important promoter of alcoholic liver disease, current results may open new therapeutic avenues and revolutionize the current understanding of chronic liver diseases.

Trial registration

EudraCT, 2014–001856-51. Registered on 16 August 2014.

Electronic supplementary material

The online version of this article (10.1186/s13063-018-2523-9) contains supplementary material, which is available to authorized users.

New therapeutic perspectives in irritable bowel syndrome: Targeting low-grade inflammation, immuno-neuroendocrine axis, motility, secretion and beyond

Irritable bowel syndrome (IBS) is a chronic, recurring, and remitting functional disorder of the gastrointestinal tract characterized by abdominal pain, distention, and changes in bowel habits. Although there are several drugs for IBS, effective and approved treatments for one or more of the symptoms for various IBS subtypes are needed. Improved understanding of pathophysiological mechanisms such as the role of impaired bile acid metabolism, neurohormonal regulation, immune dysfunction, the epithelial barrier and the secretory properties of the gut has led to advancements in the treatment of IBS. With regards to therapies for restoring intestinal permeability, multiple studies with prebiotics and probiotics are ongoing, even if to date their efficacy has been limited. In parallel, much progress has been made in targeting low-grade inflammation, especially through the introduction of drugs such as mesalazine and rifaximin, even if a better knowledge of the mechanisms underlying the low-grade inflammation in IBS may allow the design of clinical trials that test the efficacy and safety of such drugs. This literature review aims to summarize the findings related to new and investigational therapeutic agents for IBS, most recently developed in preclinical as well as Phase 1 and Phase 2 clinical studies.

Rifaximin versus norfloxacin for prevention of spontaneous bacterial peritonitis: a systematic review

Aim

The aim of this systematic review is to evaluate the efficacy and safety of rifaximin in the prophylaxis of spontaneous bacterial peritonitis (SBP) as compared with norfloxacin.

Methods

We searched MEDLINE, CINAHL, Google Scholar and Cochrane databases from inception to January 2017. Reference lists of articles as well as conference proceedings were manually screened. We included studies that recruited patients with cirrhosis and ascites who met the criteria for primary or secondary SBP prophylaxis as defined by the European Association for the Study of the Liver and American Association for the Study of Liver Diseases. Two independent investigators reviewed the studies for eligibility, extracted the data and assessed study quality using the Cochrane risk of bias tool. The primary outcome was occurrence of SBP. Secondary outcomes included mortality and adverse events with therapy.

Results

Of the 435 studies identified, a total of five were included for full-text review. Four studies were eligible for the systematic review, three of which were randomised controlled trials and one was a prospective observational study. The population examined in majority of studies was primarily hepatitis C cirrhosis. The results of individual studies indicated either superior efficacy of rifaximin or no statistical difference between rifaximin and norfloxacin for SBP prophylaxis.

Conclusions

Moderate-quality evidence shows that long-term use of rifaximin appears to be a reasonable alternative to norfloxacin for SBP prevention in hepatitis C cirrhosis.

Antibiotic use and microbiome function

Our microbiome should be understood as one of the most complex components of the human body. The use of β-lactam antibiotics is one of the microbiome covariates that influence its composition. The extent to which our microbiota changes after an antibiotic intervention depends not only on the chemical nature of the antibiotic or cocktail of antibiotics used to treat specific infections, but also on the type of administration, duration and dose, as well as the level of resistance that each microbiota develops. We have begun to appreciate that not all bacteria within our microbiota are vulnerable or reactive to different antibiotic interventions, and that their influence on both microbial composition and metabolism may differ. Antibiotics are being used worldwide on a huge scale and the prescription of antibiotics is continuing to rise; however, their effects on our microbiota have been reported for only a limited number of them. This article presents a critical review of the antibiotics or antibiotic cocktails whose use in humans has been linked to changes in the composition of our microbial communities, with a particular focus on the gut, oral, respiratory, skin and vaginal microbiota, and on their molecular agents (genes, proteins and metabolites). We review the state of the art as of June 2016, and cover a total of circa 68 different antibiotics. The data herein are the first to compile information about the bacteria, fungi, archaea and viruses most influenced by the main antibiotic treatments prescribed nowadays.

Rifaximin and diverticular disease: Position paper of the Italian Society of Gastroenterology (SIGE)

Management of diverticular disease has significantly improved in the last decade. Antibiotic treatment is used for symptom relief and prevention of complications. In Italy, the non-absorbable antibiotic rifaximin is one of the most frequently used drugs, and it is perceived as the reference drug to treat symptomatic diverticular disease. Its non-systemic absorption and high faecal concentrations have oriented rifaximin use to the gastrointestinal tract, where rifaximin exerts eubiotic effects representing an additional value to its antibiotic activity. This position paper was commissioned by the Italian Society of Gastroenterology governing board for a panel of experts (RC, GB, BA) to highlight the indications for treatment of diverticular disease. There is a lack of rationale for drug use for the primary prevention of diverticulitis in patients with diverticulosis; thus, rifaximin use should be avoided. The cyclic use of rifaximin, in association with high-fibre intake, is safe and useful for the treatment of symptomatic uncomplicated diverticular disease, even if the cost-efficacy of long-term treatment remains to be determined. The use of rifaximin in the prevention of diverticulitis recurrence is promising, but the low therapeutic advantage needs to be verified. No evidence is available on the efficacy of rifaximin treatment on acute uncomplicated diverticulitis.

Diagnosis of symptomatic uncomplicated diverticular disease and the role of Rifaximin in management

Patients with diverticulosis who develop persistent abdominal pain, bloating and changes in bowel habits not associated with overt inflammation may have symptomatic uncomplicated diverticular disease (SUDD). The severity and frequency of SUDD symptoms may have an impact on daily activities and severely affect quality of life. Effective management of SUDD should follow a three part strategy: divert, tackle and maintain. Divert to make the correct diagnosis: several symptoms of SUDD are common to other conditions that require different therapeutic approaches. However, several key differences should be used to diagnose SUDD. Pain in SUDD is normally in the iliac fossa, persistent, often lasting more than 24 hrs, and is not relieved by bowel movement, as is often the case with irritable bowel syndrome. Another difference is in the timing: the prevalence of SUDD increases with age, and patients under the age of 40 years are less likely to have diverticula. It is useful to establish whether a patient has diverticulosis, especially if the patient is relatively young; lack of diverticula excludes SUDD. Cross-sectional imaging is indicated; however, recent archival image data or ultrasonography may be useful alternatives. Laboratory tests should be ordered to exclude overt inflammation. Once the diagnosis of SUDD is made, the patient should receive effective therapy to tackle the condition. This should include dietary fibre supplementation and cyclic treatment with rifaximin 400 mg twice daily for 7 days per month. Once symptom control is achieved, it should be maintained by continuing therapy for at least 12 months. (www.actabiomedica.it)

Use of antimicrobial agents for treatment and prevention of travellers' diarrhoea in the face of enhanced risk of transient fecal carriage of multi-drug resistant enterobacteriaceae: setting the stage for consensus recommendations

BACKGROUND

The recommendation that antibiotics should be used for routine therapy of travellers' diarrhoea is being reconsidered in view of growing evidence that the therapy may lead to intestinal carriage of multi-drug resistant (MDR) colonic microbiota. This review attempts to put the issues of therapy and MDR acquisition in perspective to help in the establishment of therapeutic recommendations for travellers' diarrhoea.

METHODS

The existing literature showing the risk and consequences of acquisition of MDR microbiota in antibiotic-treated travellers was reviewed. Issues important to the development of firm evidence-based recommendations for antibiotics use for treatment and prevention of travellers' diarrhoea were researched.

RESULTS

Six areas of research needed to allow the development of evidence-based recommendations for antibiotic-treatment and -prevention of travellers' diarrhoea were identified.

CONCLUSIONS

Increasing worldwide occurrence of antibiotic resistance should alert public health officials of the importance of encouraging local antibiotic stewardship guidelines. Six areas to research are identified in this review to allow the development of evidence-based recommendations for use of antibiotics for treatment and selective prevention of travellers' diarrhoea. An interdisciplinary ISTM Consensus group will consider the data available and develop current recommendations for therapy and chemoprevention of travellers' diarrhoea considering groups who would benefit the most from antimicrobials while recognizing the hazards associated with broad use of these drugs. With interim recommendations and ultimately evidence-based recommendations, guidelines can be developed for management of travellers' diarrhoea considering populations and destinations.

Randomised clinical trial: rifaximin versus placebo for the treatment of functional dyspepsia

BACKGROUND

Gut dysbiosis may contribute to pain and bloating in patients with functional gastrointestinal disease.

AIMS

To determine if treatment with rifaximin would improve the symptoms of functional dyspepsia in Chinese patients in a double-blinded, randomised, placebo-controlled trial.

METHODS

Consecutive subjects with a diagnosis of functional dyspepsia as per the Rome III criteria were randomised to receive rifaximin 400 mg or placebo, all taken three times daily for 2 weeks. The investigators and study subjects were blinded to the treatment allocation. Subjects were followed up for 8 weeks. The primary end point was adequate relief of global dyspeptic symptoms (GDS). Secondary endpoints were relief of individual dyspeptic symptoms.

RESULTS

Eighty-six subjects were recruited. At week 8, there were significantly more subjects in the rifaximin than in the placebo group who experienced adequate relief of GDS (78% vs. 52%, P = 0.02). A trend favouring rifaximin group was also noted in the preceding 4 weeks. Rifaximin was also superior to placebo in providing adequate relief of belching and post-prandial fullness/bloating (PPF) in subjects at week 4. Subgroup analysis revealed that female subjects had more significant response to rifaximin treatment (adequate relief of GDS at week 4: 76% vs. 42%, P = 0.006; week 8: 79% vs. 47%, P = 0.008), as well as improvements in their belching and PPF at week 4. The incidences of adverse effects were similar in both groups.

CONCLUSIONS

Treatment with 2 weeks of rifaximin led to adequate relief of global dyspeptic symptoms, belching and post-prandial fullness/bloating in subjects with functional dyspepsia. The difference was more marked in females. (clinicaltrials.org NCT01643083).

Microbiota Disruption Induced by Early Use of Broad-Spectrum Antibiotics Is an Independent Risk Factor of Outcome after Allogeneic Stem Cell Transplantation

In allogeneic stem cell transplantation (ASCT), systemic broad-spectrum antibiotics are frequently used for treatment of infectious complications, but their effect on microbiota composition is still poorly understood. This retrospective analysis of 621 patients who underwent ASCT at the University Medical Center of Regensburg and Memorial Sloan Kettering Cancer Center in New York assessed the impact of timing of peritransplant antibiotic treatment on intestinal microbiota composition as well as transplant-related mortality (TRM) and overall survival. Early exposure to antibiotics was associated with lower urinary 3-indoxyl sulfate levels (P < .001) and a decrease in fecal abundance of commensal Clostridiales (P = .03) compared with late antibiotic treatment, which was particularly significant (P = .005) for Clostridium cluster XIVa in the Regensburg group. Earlier antibiotic treatment before ASCT was further associated with a higher TRM (34%, 79/236) compared with post-ASCT (21%, 62/297, P = .001) or no antibiotics (7%, 6/88, P < .001). Timing of antibiotic treatment was the dominant independent risk factor for TRM (HR, 2.0; P ≤ .001) in multivariate analysis besides increase age (HR, 2.15; P = .004), reduced Karnofsky performance status (HR, 1.47; P = .03), and female donor-male recipient sex combination (HR, 1.56; P = .02) A competing risk analysis revealed the independent effect of early initiation of antibiotics on graft-versus-host disease-related TRM (P = .004) in contrast to infection-related TRM and relapse (not significant). The poor outcome associated with early administration of antibiotic therapy that is active against commensal organisms, and specifically the possibly protective Clostridiales, calls for the use of Clostridiales-sparing antibiotics and rapid restoration of microbiota diversity after cessation of antibiotic treatment.

Therapeutic Modulation of Gut Microbiota in Functional Bowel Disorders

Functional bowel disorders (FBDs) are functional gastrointestinal disorders with symptoms attributable to the middle or lower gastrointestinal tract. These include irritable bowel syndrome, functional bloating, functional constipation, functional diarrhea, and unspecified FBD. Increasing evidence has emerged of late that intestinal microbiota is involved in the pathogenesis of FBDs. In this review, the therapeutic benefits and future perspectives of the currently available strategies for modifying the gut microbiota in FBDs are described, focusing primarily on irritable bowel syndrome and functional constipation.

Gastrointestinal Pharmacology

There is little evidence for most of the medications currently used to treat functional abdominal pain disorders (FAPDs) in children. Not only are there very few clinical trials, but also most have significant variability in the methods used and outcomes measured. Thus, the decision on the most appropriate pharmacological treatment is frequently based on adult studies or empirical data. In children, peppermint oil, trimebutine, and drotaverine have shown significant benefit compared with placebo, each of them in a single randomized clinical trial. A small study found that cyproheptadine was beneficial in the treatment of FAPDs in children. There are conflicting data regarding amitriptyline. While one small study found a significant benefit in quality of life compared with placebo, a large multicenter study found no benefit compared with placebo. The antidepressant, citalopram, failed to meet the primary outcomes in intention-to-treat and per-protocol analysis. Rifaximin has been shown to be efficacious in the treatment of adults with IBS. Those findings differ from studies in children where no benefit was found compared to placebo. To date, there are no placebo-controlled trials published on the use of linaclotide or lubiprostone in children. Alpha 2 delta ligands such as gabapentin and pregabalin are sometimes used in the care of this group of children, but no clinical trials are available in children with FAPDs. Similarly, novel drugs that have been approved for the care of irritable bowel with diarrhea in adults such as eluxadoline have yet to be studied in children.

CONCLUSIONS

Little data support the use of most medications commonly used to treat FAPDs in children. More randomized, placebo-controlled studies are needed to assess the efficacy of pharmacological interventions in the treatment of FAPDs in children.

Chronic opioid use is associated with altered gut microbiota and predicts readmissions in patients with cirrhosis

BACKGROUND

Opioid use is epidemic in cirrhosis, which could precipitate hepatic encephalopathy (HE) potentially through gut dysbiosis and inflammation.

AIM

To define the effect of opioids on readmissions and on gut microbiota composition and functionality.

METHODS

Cohort 1 had 200 cirrhotic in-patients (with/without opioid use) followed prospectively through the index hospitalisation and 6 months post discharge. Readmissions (HE-related/unrelated) were compared between patients discharged on opioids compared to the rest, including using a multi-variable analysis. Cohort 2 consisted of 72 cirrhotics on chronic opioids who were age/model for end-stage liver disease (MELD) and prior HE-balanced with 72 cirrhotics not on opioids. Stool microbiota composition (multi-tagged sequencing), predicted functionality (PiCRUST), endotoxemia and systemic inflammation (IL-6, IL-17) were compared.

RESULTS

Cohort 1: Chronic opioid use was statistically similar between those admitted with/without HE, and was judged to be an HE precipitant in <5% of cases during the index hospitalisation. Of the 144 patients alive at 6 months, 82 were readmitted. The opioid users had a significantly higher all cause (69% vs. 48%, P = 0.008), but not HE-related readmissions (30% vs. 41%, P = 0.30). On regression, opioid therapy and female gender were predictive of readmission independent of MELD score and previous HE. Cohort 2: Significant dysbiosis was noted in the opioid cohort, especially in HE+opioid patients with lower autochthonous taxa and Bacteroidaceae relative abundance. PiCRUST showed highest aromatic amino acid and endotoxin production in opioid users. Opioid users also had higher endotoxemia and IL-6 but not IL-17.

CONCLUSION

Chronic opioid use in cirrhosis is associated with increased endotoxemia, dysbiosis and all-cause readmissions.

Rifaximin for the treatment of diarrhea-predominant irritable bowel syndrome

Irritable bowel syndrome (IBS) is a chronic, functional bowel disorder characterized by abdominal pain or discomfort and altered bowel habit. The pathophysiology is unclear, but may include altered gut motility, visceral hypersensitivity, abnormal central pain processing, chronic low-grade intestinal inflammation, or disturbances in the gut microbiome. These etiological mechanisms, alongside environmental factors such as stress and anxiety, vary between individuals and represent potential targets for treatment. Rifaximin is a poorly absorbed oral antibiotic proposed to act on the gut microenvironment, used in the treatment of travelers' diarrhea and hepatic encephalopathy. Clinical trials suggest the drug can reduce global IBS symptoms and improve bloating, abdominal pain, and stool consistency in some patients with non-constipated IBS, leading to Food and Drug Administration approval in the United States. This article considers the pharmacology of rifaximin, the evidence for its use in IBS, and the safety and tolerability of the drug.

The challenges of multi-drug-resistance in hepatology

Antimicrobial resistance has become a major global public health security problem that needs coordinated approaches at regional, national and international levels. Antibiotic overuse and the failure of control measures to prevent the spread of resistant bacteria in the healthcare environment have led to an alarming increase in the number of infections caused by resistant bacteria, organisms that resist many (multi-drug and extensively drug-resistant strains), if not all (pan-drug-resistant bacteria) currently available antibiotics. While Gram-positive cocci resistance (methicillin-resistant Staphylococcus aureus and vancomycin-resistant enterococci) shows a heterogeneous geographical distribution, extended-spectrum β-lactamase-producing Enterobacteriaceae and carbapenem-resistant Enterobacteriaceae have become pandemic worldwide and endemic in some parts of the world, respectively. Moreover, currently available therapeutic options for resistant bacteria are very limited, with very few new agents in development. Antimicrobial resistance is especially relevant in decompensated cirrhosis. Firstly, cirrhotic patients are highly susceptible to develop infections caused by resistant bacteria as risk factors of multiresistance concentrate in this population (mainly repeated hospitalizations and antibiotic exposure). Secondly, inappropriate empirical antibiotic schedules easily translate into increased morbidity (acute kidney injury, acute-on-chronic liver failure, septic shock) and hospital mortality in advanced cirrhosis. Therefore, hepatologists must face nowadays a complex clinical scenario that requires new empirical antibiotic strategies that may further spread resistance. Global, regional and local preventive measures should therefore be implemented to combat antimicrobial resistance in cirrhosis including the restriction of antibiotic prophylaxis to high-risk populations, investigation on non-antibiotic prophylaxis, stewardship programs on adequate antibiotic prescription and on increasing awareness of the problem among health professionals, and well-defined early de-escalation policies based on rapid microbiological diagnostic tests. Other infection control practices such as hand hygiene and barrier precautions are also important. Clinical impact and cost-effectiveness of epidemiological surveillance programs (periodic rectal and nasal swabs) should also be explored.