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Background/Objective: Rifaximin is a nonabsorbable antibiotic used to treat irritable bowel syndrome (IBS). Recent studies on Helicobacter pylori eradication treatment have reported synergistic effects and low adverse effects when antibiotics are used in combination with probiotics; yet, such studies have not been conducted in IBS. Probiotics can enhance gut microbiota modulation, inhibition of pathogen adhesion to the gut epithelia, improvement in gut barrier function, anti-inflammatory effects, and improvement of gut immunity. Therefore, this study aimed to investigate the efficacy and safety of rifaximin in combination with probiotics compared to rifaximin monotherapy in patients with IBS. Methods: Patients with IBS were randomly allocated to receive rifaximin monotherapy or a combination of rifaximin and probiotics. The primary outcome was the response rate of the total IBS severity scoring system (IBS-SSS) score (>50-point decrease). Secondary outcomes were based on the response rate of the IBS quality of life (IBS-QOL) score and the IBS-SSS1 subscore (>10-point decrease in both scores). Results: Among 70 patients, the responder rates for the total IBS-SSS score were 65.7% in the combination therapy group and 31.4% in the monotherapy group at weeks 4 and 8, respectively (p = 0.004). The responder rates for IBS-QOL were 65.7% versus (vs.) 37.1% and 65.7% vs. 34.2% at weeks 4 and 8, respectively (p = 0.017 and p = 0.009, respectively). The IBS-SSS1 subscore responder rates were 65.7% vs. 40.0% at week 4 and 68.6% vs. 37.1% at 8 weeks (p = 0.031 and p = 0.017, respectively). Conclusions: Rifaximin combined with probiotics was superior to rifaximin monotherapy in patients with IBS. This combination therapy is considered an effective and safe treatment option for patients with IBS. However, further studies are needed to investigate the mechanisms of therapy and long-term outcomes.

BackgroundIrritable bowel syndrome (IBS) occurs in up to 33% of Gulf War (GW) Veterans. Alterations in gut microflora including small intestinal bacterial overgrowth (SIBO) during deployment may play a role in development of IBS. Rifaximin is a minimally absorbed antibiotic speculated to improve IBS symptoms, in part, by restoring normal gut microflora. The aim of this study was to compare rifaximin to placebo on IBS symptoms and quality of life (QOL) in GW Veterans with IBS without constipation.MethodsA double-blind, placebo-controlled study was performed. One hundred and twenty-two GW Veterans with IBS (Rome III) from our database and referral to gastroenterology and internal medicine clinics were screened. After a 2-week run-in period, 50 patients were randomized (1:1) to receive either rifaximin 550 gm or placebo twice daily for 2 weeks in a double-blind study. Patients were advised not to change their diet or medications during the study. The symptoms assessed were: (1) stool frequency, (2) stool consistency (Bristol stool scale, 1–7, very hard to watery), (3) urgency (1 = yes/0 = no daily for 7 days), (4) severity of abdominal pain (0–4, none to severe), (5) severity of bloating (1–4, none to severe), and (6) global improvement scale (1–7, substantially worse to substantially improved). These were recorded for 7 consecutive days and then averaged across the 7 days, to generate a continuous variable. The symptom data were compared after 2 weeks of treatment. QOL was assessed using IBS-QOL. The lactulose hydrogen breath test (LHBT) was performed at baseline and after 2 weeks of treatment.ResultsFifty Veterans were randomized to receive treatment; 3 withdrew and 3 were lost to follow-up. Data were analyzed from 44 patients (38 men, 6 women, median age 52, range 33–77 years). Rifaximin was not associated with significant improvement in global symptoms, abdominal pain, bloating, stool urgency, frequency, or consistency (all P ≥ 0.25) or QOL (all P ≥ 0.26). Normalization of SIBO by LHBT was not different between rifaximin- and placebo-treated Veterans (7 vs. 22%, P = 0. 54).ConclusionRifaximin was not effective in improving IBS symptoms and QOL in GW Veterans with non-constipated IBS.

Multidrug-resistant bacterial pathogens like vancomycin-resistant Enterococcus faecium (VREfm) are a critical threat to human health 1 . Daptomycin is a last-resort antibiotic for VREfm infections with a novel mode of action 2 , but for which resistance has been widely reported but is unexplained. Here we show that rifaximin, an unrelated antibiotic used prophylactically to prevent hepatic encephalopathy in patients with liver disease 3 , causes cross-resistance to daptomycin in VREfm. Amino acid changes arising within the bacterial RNA polymerase in response to rifaximin exposure cause upregulation of a previously uncharacterized operon ( prdRAB ) that leads to cell membrane remodelling and cross-resistance to daptomycin through reduced binding of the antibiotic. VREfm with these mutations are spread globally, making this a major mechanism of resistance. Rifaximin has been considered ‘low risk’ for the development of antibiotic resistance. Our study shows that this assumption is flawed and that widespread rifaximin use, particularly in patients with liver cirrhosis, may be compromising the clinical use of daptomycin, a major last-resort intervention for multidrug-resistant pathogens. These findings demonstrate how unanticipated antibiotic cross-resistance can undermine global strategies designed to preserve the clinical use of critical antibiotics. Rifaximin use, particularly in patients with liver cirrhosis, may be compromising the clinical use of daptomycin.

INTRODUCTION:Critically ill patients with cirrhosis admitted to the intensive care unit (ICU) are usually on broad-spectrum antibiotics because of suspected infection or as a hospital protocol. It is unclear if additional rifaximin has any synergistic effect with broad-spectrum antibiotics in ICU patients with acute overt hepatic encephalopathy (HE).METHODS:In this double-blind trial, patients with overt HE admitted to ICU were randomized to receive antibiotics (ab) alone or antibiotics with rifaximin (ab + r). Resolution (or 2 grade reduction) of HE, time to resolution of HE, in-hospital mortality, nosocomial infection, and changes in endotoxin levels were compared between the 2 groups. A subgroup analysis of patients with decompensated cirrhosis and acute-on-chronic liver failure was performed.RESULTS:Baseline characteristics and severity scores were similar among both groups (92 in each group). Carbapenems and cephalosporin with beta-lactamase inhibitors were the most commonly used ab. On Kaplan-Meier analysis, 44.6% (41/92; 95% confidence interval [CI], 32-70.5) in ab-only arm and 46.7% (43/92; 95% CI, 33.8-63) in ab + r arm achieved the primary objective (P = 0.84).Time to achieve the primary objective (3.65 ± 1.82 days and 4.11 ± 2.01 days; P = 0.27) and in-hospital mortality were similar among both groups (62% vs 50%; P = 0.13). Seven percent and 13% in the ab and ab + r groups developed nosocomial infections (P = 0.21). Endotoxin levels were unaffected by rifaximin. Rifaximin led to lower in-hospital mortality (hazard ratio: 0.39 [95% CI, 0.2-0.76]) in patients with decompensated cirrhosis but not in patients with acute-on-chronic liver failure (hazard ratio: 0.99 [95% CI, 0.6-1.63]) because of reduced nosocomial infections.DISCUSSION:Reversal of overt HE in those on ab was comparable with those on ab + r.

Compounds featuring a 1,2,4-oxadiazole core have been recently identified as a new chemotype of farnesoid X receptor (FXR) antagonists. With the aim to expand this class of compounds and to understand the building blocks necessary to maintain the antagonistic activity, we describe herein the synthesis, the pharmacological evaluation, and the in vitro pharmacokinetic properties of a novel series of 1,2,4-oxadiazole derivatives decorated on the nitrogen of the piperidine ring with different N-alkyl and N-aryl side chains. In vitro pharmacological evaluation showed compounds 5 and 11 as the first examples of nonsteroidal dual FXR/Pregnane X receptor (PXR) modulators. In HepG2 cells, these compounds modulated PXR- and FXR-regulated genes, resulting in interesting leads in the treatment of inflammatory disorders. Moreover, molecular docking studies supported the experimental results, disclosing the ligand binding mode and allowing rationalization of the activities of compounds 5 and 11.

Probiotics that promote the gut microbiota have been reported to reduce stress responses, and improve memory and mood. Whether and how antibiotics that eliminate or inhibit pathogenic and commensal gut bacteria also affect central nervous system functions in humans is so far unknown. In a double-blinded randomized study, 16 healthy volunteers (27.00 ± 1.60 years; 9 males) received either rifaximin (600 mg/day) (a poorly absorbable antibiotic) or placebo for 7 days. Before and after the drug intervention, brain activities during rest and during a social stressor inducing feelings of exclusion (Cyberball game) were measured using magnetoencephalography. Social exclusion significantly affected (p < 0.001) mood and increased exclusion perception. Magnetoencephalography showed brain regions with higher activations during exclusion as compared to inclusion, in different frequency bands. Seven days of rifaximin increased prefrontal and right cingulate alpha power during resting state. Low beta power showed an interaction of intervention (rifaximin, placebo) × condition (inclusion, exclusion) during the Cyberball game in the bilateral prefrontal and left anterior cingulate cortex. Only in the rifaximin group, a decrease (p = 0.004) in power was seen comparing exclusion to inclusion; the reduced beta-1 power was negatively correlated with a change in the subjective exclusion perception score. Social stress affecting brain functioning in a specific manner is modulated by rifaximin. Contrary to our hypothesis that antibiotics have advert effects on mood, the antibiotic exhibited stress-reducing effects similar to reported effects of probiotics (supported by NeuroGUT, a EU 7th Framework Programme ITN no. 607652; ClinicalTrials.gov identifier number NCT02793193).

Alcoholic hepatitis (AH) is characterized by acute liver failure, neurocognitive impairment and renal failure. Severe inflammatory reactions are also known to occur in AH. Inflammation and bacterial translocation in the gut are thought to have major impact on disease development and progression. The mortality rate for AH is close to 50%. We aimed to assess the efficacy of rifaximin in treating AH and its impact on inflammation and metabolism. The trial was approved by relevant authorities (EudraCT no: 2014-02264-33, Scientific Ethics Committee, jr. no: H-1-2014-056). Primary outcomes were changes in metabolic and inflammatory markers. Secondary outcomes were portal hypertension, kidney and neurocognitive function. Thirty-two patients were randomized to standard medical therapy (SMT) or SMT plus rifaximin, allocation was concealed. Four patients in the SMT group and five patients in the SMT + rifaximin group died due to AH and liver failure. No adverse events related to the study medication were observed. We found no significant differences in amino acids or inflammation markers (IL-2, IL-6, IL-8, IL-10, TNF-α, interferon-γ) between the groups after 28 and 90 days. Rifaximin does not alter inflammation or metabolism in patients with AH.

Background and Aim. Variceal bleeding is the second most important precipitating factor related to the development of episodic hepatic encephalopathy; but to date there are no recommendations to prevent this complication. The aim of this study was to compare if primary prophylaxis with lactulose or L-ornithine L-aspartate or rifaximin, in cirrhotic patients with variceal bleeding, is better than placebo for avoiding the development of hepatic encephalopathy. Methods. A randomized, double-blind, placebo-controlled clinical trial (ClinicalTrials.gov identifier: NCT02158182) which included cirrhotic patients with variceal bleeding, without minimal or clinical hepatic encephalopathy at admission. Findings. 87 patients were randomized to one of four groups. The basal characteristics were similar between groups. Comparatively with placebo, the frequency with regard to the development of hepatic encephalopathy was as follows: lactulose (54.5% versus 27.3%; OR = 0.3, 95% CI 0.09-1.0; P = 0.06); L-ornithine L-aspartate (54.5% versus 22.7%, OR = 0.2, 95% CI 0.06-0.88; P = 0.03); rifaximin (54.5% versus 23.8%; OR = 0.3, 95% CI 0.07-0.9; P = 0.04). There was no significant difference between the three groups receiving any antiammonium drug (P = 0.94). In the group receiving lactulose, 59.1% had diarrhea, and 45.5% had abdominal discomfort, bloating, and flatulence. Two patients (10%) treated with lactulose and a patient (4.5%) in the placebo group developed spontaneous bacterial peritonitis due to E. coli; one of them died due to recurrent variceal bleeding. There were no other adverse effects. Conclusions. Antiammonium drugs, particularly L-ornithine L-aspartate and rifaximin, proved to be effective in preventing the development of hepatic encephalopathy in those cirrhotic patients with variceal bleeding.

Background Chronic unpredictable mild stress (CUMS) can not only lead to depression-like behavior but also change the composition of the gut microbiome. Regulating the gut microbiome can have an antidepressant effect, but the mechanism by which it improves depressive symptoms is not clear. Short-chain fatty acids (SCFAs) are small molecular compounds produced by the fermentation of non-digestible carbohydrates. SFCAs are ubiquitous in intestinal endocrine and immune cells, making them important mediators of gut microbiome-regulated body functions. The balance between the pro- and anti-inflammatory microglia plays an important role in the occurrence and treatment of depression caused by chronic stress. Non-absorbable antibiotic rifaximin can regulate the structure of the gut microbiome. We hypothesized that rifaximin protects against stress-induced inflammation and depression-like behaviors by regulating the abundance of fecal microbial metabolites and the microglial functions. Methods We administered 150 mg/kg rifaximin intragastrically to rats exposed to CUMS for 4 weeks and investigated the composition of the fecal microbiome, the content of short-chain fatty acids in the serum and brain, the functional profiles of microglia and hippocampal neurogenesis. Results Our results show that rifaximin ameliorated depressive-like behavior induced by CUMS, as reflected by sucrose preference, the open field test and the Morris water maze. Rifaximin increased the relative abundance of Ruminococcaceae and Lachnospiraceae, which were significantly positively correlated with the high level of butyrate in the brain. Rifaximin increased the content of anti-inflammatory factors released by microglia, and prevented the neurogenic abnormalities caused by CUMS. Conclusions These results suggest that rifaximin can regulate the inflammatory function of microglia and play a protective role in pubertal neurodevelopment during CUMS by regulating the gut microbiome and short-chain fatty acids.