Pretreatment of epithelial cells with rifaximin alters bacterial attachment and internalization profiles

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.

Aryl hydrocarbon receptor (AhR) and pregnane X receptor (PXR) play both distinct and common roles in the regulation of colon homeostasis and intestinal carcinogenesis

Both aryl hydrocarbon receptor (AhR) and pregnane X receptor (PXR) belong among key regulators of xenobiotic metabolism in the intestinal tissue. AhR in particular is activated by a wide range of environmental and dietary carcinogens. The data accumulated over the last two decades suggest that both of these transcriptional regulators play a much wider role in the maintenance of gut homeostasis, and that both transcription factors may affect processes linked with intestinal tumorigenesis. Intestinal epithelium is continuously exposed to a wide range of AhR, PXR and dual AhR/PXR ligands formed by intestinal microbiota or originating from diet. Current evidence suggests that specific ligands of both AhR and PXR can protect intestinal epithelium against inflammation and assist in the maintenance of epithelial barrier integrity. AhR, and to a lesser extent also PXR, have been shown to play a protective role against inflammation-induced colon cancer, or, in mouse models employing overactivation of Wnt/β-catenin signaling. In contrast, other evidence suggests that both receptors may contribute to modulation of transformed colon cell behavior, with a potential to promote cancer progression and/or chemoresistance. The review focuses on both overlapping and separate roles of the two receptors in these processes, and on possible implications of their activity within the context of intestinal tissue.

Future Modulation of Gut Microbiota: From Eubiotics to FMT, Engineered Bacteria, and Phage Therapy

The human gut is inhabited by a multitude of bacteria, yeasts, and viruses. A dynamic balance among these microorganisms is associated with the well-being of the human being, and a large body of evidence supports a role of dysbiosis in the pathogenesis of several diseases. Given the importance of the gut microbiota in the preservation of human health, probiotics, prebiotics, synbiotics, and postbiotics have been classically used as strategies to modulate the gut microbiota and achieve beneficial effects for the host. Nonetheless, several molecules not typically included in these categories have demonstrated a role in restoring the equilibrium among the components of the gut microbiota. Among these, rifaximin, as well as other antimicrobial drugs, such as triclosan, or natural compounds (including evodiamine and polyphenols) have common pleiotropic characteristics. On one hand, they suppress the growth of dangerous bacteria while promoting beneficial bacteria in the gut microbiota. On the other hand, they contribute to the regulation of the immune response in the case of dysbiosis by directly influencing the immune system and epithelial cells or by inducing the gut bacteria to produce immune-modulatory compounds, such as short-chain fatty acids. Fecal microbiota transplantation (FMT) has also been investigated as a procedure to restore the equilibrium of the gut microbiota and has shown benefits in many diseases, including inflammatory bowel disease, chronic liver disorders, and extraintestinal autoimmune conditions. One of the most significant limits of the current techniques used to modulate the gut microbiota is the lack of tools that can precisely modulate specific members of complex microbial communities. Novel approaches, including the use of engineered probiotic bacteria or bacteriophage-based therapy, have recently appeared as promising strategies to provide targeted and tailored therapeutic modulation of the gut microbiota, but their role in clinical practice has yet to be clarified. The aim of this review is to discuss the most recently introduced innovations in the field of therapeutic microbiome modulation.

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.

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

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

Microbiome therapeutics for hepatic encephalopathy

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

Review of Rifaximin: A Summary of the Current Evidence and Benefits Beyond Licensed Use

Antibiotic resistance in patients with cirrhosis continues to draw significant attention. With a propensity to frequent hospitalisations, patients with cirrhosis are subject to frequent antibiotic prescription. This increases their risk of developing resistance to one or more antimicrobial agents, making management of their condition particularly challenging. Despite advancements being made in the management of liver disease, mortality rates continue to rise: almost 5-fold in those <65 years of age while remaining the leading cause of death in those 35–49 years of age. Alternative therapeutic options to prevent disease progression and cirrhosis-associated complications are urgently required; rifaximin is one such example. The medication use in patients with cirrhosis demonstrates additional benefits beyond current licensed use in the UK, that being for the prevention of hepatic encephalopathy and traveller’s diarrhoea; rifaximin has especially been explored beyond current licensed use in the context of enteric-driven pathologies. Through the therapy’s key central action as a broad-spectrum antimicrobial, rifaximin has the ability to modulate the gut–liver axis via removal of gut microbial products associated with the progression of cirrhosis and its sequalae. The benefits of rifaximin use continues to gather momentum, given its non-absorbable nature and well-tolerated side-effect profile, and these require consideration. With broad-spectrum antimicrobial properties, its use may assist in overcoming the conundrum posed of antibiotic resistance amongst patients with cirrhosis. This literature review discusses the chemical and antimicrobial properties of rifaximin, its licenced indication for use, and its reported benefits beyond this, as well as concerns regarding rifaximin resistance.

Perioperative rifaximin is not associated with enhanced functional and volumetric recovery after major liver resection

The objective of this randomized controlled trial (RCT) was to assess the impact of rifaximin on the course of liver function, liver regeneration and volumetric recovery in patients undergoing major hepatectomy. The ARROW trial was an investigator initiated, single-center, open-label, phase 3 RCT with two parallel treatment groups, conducted at our hepatobiliary center from 03/2016 to 07/2020. Patients undergoing major hepatectomy were eligible and randomly assigned 1:1 to receive oral rifaximin (550 mg twice daily for 7-10 or 14-21 days in case of portal vein embolization preoperatively and 7 days postoperatively) versus no intervention. Primary endpoint was the relative increase in postoperative liver function measured by LiMAx from postoperative day (POD) 4 to 7. Secondary endpoint were the course of liver function and liver volume during the study period as well as postoperative morbidity and mortality. Between 2016 and 2020, 45 patients were randomized and 35 patients (16 individuals in the rifaximin and 19 individuals in the control group) were eligible for per-protocol analysis. The study was prematurely terminated following interim analysis, due to the unlikelihood of reaching a significant primary endpoint. The median relative increase in liver function from POD 4 to POD 7 was 27% in the rifaximin group and 41% in the control group (p = 0.399). Further, no significant difference was found in terms of any other endpoints of functional liver- and volume regeneration or perioperative surgical complications following the application of rifaximin versus no intervention. Perioperative application of rifaximin has no effect on functional or volumetric regeneration after major hepatectomy (NCT02555293; EudraCT 2013-004644-28).

Natural and synthetic antimicrobials reduce adherence of enteroaggregative and enterohemorrhagic Escherichia coli to epithelial cells

Adherence of bacteria to the human intestinal mucosa can facilitate their internalization and the development of pathological processes. Escherichia coli O104:H4 is considered a hybrid strain (enteroaggregative hemorrhagic E. coli [EAHEC]), sharing virulence factors found in enterohemorrhagic (EHEC), and enteroaggregative (EAEC) E. coli pathotypes. The objective of this study was to analyze the effects of natural and synthetic antimicrobials (carvacrol, oregano extract, brazilin, palo de Brasil extract, and rifaximin) on the adherence of EHEC O157:H7, EAEC 042, and EAHEC O104:H4 to HEp-2 cells and to assess the expression of various genes involved in this process. Two concentrations of each antimicrobial that did not affect (p≤0.05) bacterial viability or damage the bacterial membrane integrity were used. Assays were conducted to determine whether the antimicrobials alter adhesion by affecting bacteria and/or alter adhesion by affecting the HEp-2 cells, whether the antimicrobials could detach bacteria previously adhered to HEp-2 cells, and whether the antimicrobials could modify the adherence ability exhibited by the bacteria for several cycles of adhesion assays. Giemsa stain and qPCR were used to assess the adhesion pattern and gene expression, respectively. The results showed that the antimicrobials affected the adherence abilities of the bacteria, with carvacrol, oregano extract, and rifaximin reducing up to 65% (p≤0.05) of E. coli adhered to HEp-2 cells. Carvacrol (10 mg/ml) was the most active compound against EHAEC O104:H4, even altering its aggregative adhesion pattern. There were changes in the expression of adhesion-related genes (aggR, pic, aap, aggA, and eae) in the bacteria and oxidative stress-related genes (SOD1, SOD2, CAT, and GPx) in the HEp-2 cells. In general, we demonstrated that carvacrol, oregano extract, and rifaximin at sub-minimal bactericidal concentrations interfere with target sites in E. coli, reducing the adhesion efficiency.

Effects of Rifaximin on Luminal and Wall-Adhered Gut Commensal Microbiota in Mice

Rifaximin is a broad-spectrum antibiotic that ameliorates symptomatology in inflammatory/functional gastrointestinal disorders. We assessed changes in gut commensal microbiota (GCM) and Toll-like receptors (TLRs) associated to rifaximin treatment in mice. Adult C57BL/6NCrl mice were treated (7/14 days) with rifaximin (50/150 mg/mouse/day, PO). Luminal and wall-adhered ceco-colonic GCM were characterized by fluorescent in situ hybridization (FISH) and microbial profiles determined by terminal restriction fragment length polymorphism (T-RFLP). Colonic expression of TLR2/3/4/5/7 and immune-related markers was assessed (RT-qPCR). Regardless the period of treatment or the dose, rifaximin did not alter total bacterial counts or bacterial biodiversity. Only a modest increase in Bacteroides spp. (150 mg/1-week treatment) was detected. In control conditions, only Clostridium spp. and Bifidobacterium spp. were found attached to the colonic epithelium. Rifaximin showed a tendency to favour their adherence after a 1-week, but not 2-week, treatment period. Minor up-regulation in TLRs expression was observed. Only the 50 mg dose for 1-week led to a significant increase (by 3-fold) in TLR-4 expression. No changes in the expression of immune-related markers were observed. Rifaximin, although its antibacterial properties, induces minor changes in luminal and wall-adhered GCM in healthy mice. Moreover, no modulation of TLRs or local immune systems was observed. These findings, in normal conditions, do not rule out a modulatory role of rifaximin in inflammatory and or dysbiotic states of the gut.

Prevention of hepatic encephalopathy by administration of rifaximin and lactulose in patients with liver cirrhosis undergoing placement of a transjugular intrahepatic portosystemic shunt (TIPS): a multicentre randomised, double blind, placebo controlled trial (PEARL trial)

Introduction

Cirrhotic patients with portal hypertension can suffer from variceal bleeding or refractory ascites and can benefit from a transjugular intrahepatic portosystemic shunt (TIPS). Post-TIPS hepatic encephalopathy (HE) is a common (20%–54%) and often severe complication. A prophylactic strategy is lacking.

Methods and analysis

The Prevention of hepatic Encephalopathy by Administration of Rifaximin and Lactulose in patients with liver cirrhosis undergoing placement of a TIPS (PEARL) trial, is a multicentre randomised, double blind, placebo controlled trial. Patients undergoing covered TIPS placement are prescribed either rifaximin 550 mg two times per day and lactulose 25 mL two times per day (starting dose) or placebo 550 mg two times per day and lactulose 25 mL two times per day from 72 hours before and until 3 months after TIPS placement. Primary endpoint is the development of overt HE (OHE) within 3 months (according to West Haven criteria). Secondary endpoints include 90-day mortality; development of a second episode of OHE; time to development of episode(s) of OHE; development of minimal HE; molecular changes in peripheral and portal blood samples; quality of life and cost-effectiveness. The total sample size is 238 patients and recruitment period is 3 years in six hospitals in the Netherlands and one in Belgium.

Ethics and dissemination

This study protocol was approved in the Netherlands by the Medical Research Ethics Committee of the Academic Medical Centre, Amsterdam (2018-332), in Belgium by the Ethics Committee Research UZ/KU Leuven (S62577) and competent authorities. This study will be conducted in accordance with Good Clinical Practice guidelines and the principles of the Declaration of Helsinki. Study results will be submitted for publication in a peer-reviewed journal.

Trial registration numbers

ClinicalTrials.gov (NCT04073290) and EudraCT database (2018-004323-37).

Systemic review and network meta-analysis: Prophylactic antibiotic therapy for spontaneous bacterial peritonitis

BACKGROUND

Spontaneous bacterial peritonitis (SBP) is an important prognostic factor for outcomes in patients with cirrhosis. Antibiotic prophylaxis is recommended in patients at high risk for developing SBP, but the choice of antibiotics remains unclear.

AIM

To evaluate the efficacy of various antibiotics for prophylaxis of SBP based on randomized control trials (RCTs).

METHODS

Electronic databases were searched through November 2018 for RCTs evaluating the efficacy of therapies for primary or secondary prophylaxis of SBP. The primary outcome was the development of SBP. Sensitivity analyses limited to studies of primary or secondary prophylaxis and studies reported after 2010 were performed. The secondary outcome was the risk of all-cause mortality or transplant. The outcomes were assessed by rank of therapies based on network meta-analyses. Individual meta-analyses were also performed.

RESULTS

Thirteen RCTs (1742 patients) including norfloxacin, ciprofloxacin, rifaximin, trimethoprim-sulfamethoxazole (TMP-SMX), or placebo/no comparator were identified. Individual meta-analyses showed superiority of rifaximin over norfloxacin as well as norfloxacin and TMP-SMX over placebo. Network meta-analysis demonstrated the rank of efficacy in reducing the risk of SBP as: Rifaximin, ciprofloxacin, TMP-SMX, norfloxacin, and placebo/no comparator. Rifaximin ranked highest in sensitivity analyses limited to studies of primary or secondary prophylaxis and studies reported after 2010. Similarly, rifaximin ranked highest in reducing the risk of death/transplant.

CONCLUSION

The present comprehensive network meta-analysis provides RCT based evidence for superior efficacy of rifaximin compared to other antibiotics for the prophylaxis of SBP and reducing risk of death/transplant. Further RCTs are warranted to confirm our findings.

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

BACKGROUND

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

AIM

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

METHODS

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

RESULTS

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

CONCLUSION

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

Clinical Management of the Microbiome in Irritable Bowel Syndrome

Background

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

Methods

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

Results

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

Conclusion

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

Review article: emerging role of the gut microbiome in the progression of nonalcoholic fatty liver disease and potential therapeutic implications

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) is a prevalent disorder associated with obesity and diabetes. Few treatment options are effective for patients with NAFLD, but connections between the gut microbiome and NAFLD and NAFLD-associated conditions suggest that modulation of the gut microbiota could be a novel therapeutic option.

AIM

To examine the effect of the gut microbiota on pathophysiologic causes of NAFLD and assess the potential of microbiota-targeting therapies for NAFLD.

METHODS

A PubMed search of the literature was performed; relevant articles were included.

RESULTS

The composition of bacteria in the gastrointestinal tract can enhance fat deposition, modulate energy metabolism and alter inflammatory processes. Emerging evidence suggests a role for the gut microbiome in obesity and metabolic syndrome. NAFLD is often considered the hepatic manifestation of metabolic syndrome, and there has been tremendous progress in understanding the association of gut microbiome composition with NAFLD disease severity. We discuss the role of the gut microbiome in NAFLD pathophysiology and whether the microbiome composition can differentiate the two categories of NAFLD: nonalcoholic fatty liver (NAFL, the non-progressive form) vs nonalcoholic steatohepatitis (NASH, the progressive form). The association between gut microbiome and fibrosis progression in NAFLD is also discussed. Finally, we review whether modulation of the gut microbiome plays a role in improving treatment outcomes for patients with NAFLD.

CONCLUSIONS

Multiple pathophysiologic pathways connect the gut microbiome with the pathophysiology of NAFLD. Therefore, therapeutics that effectively target the gut microbiome may be beneficial for the treatment of patients with NAFLD.

Efficacy of Aerosolized Rifaximin versus Tobramycin for Treatment of Pseudomonas aeruginosa Pneumonia in Mice

Pseudomonas aeruginosa is a Gram-negative opportunistic bacterial pathogen that can cause chronic lung infections in patients with cystic fibrosis (CF). The current preferred treatment for CF lung infections includes inhaled tobramycin (TOB); however, studies suggest TOB cannot effectively inhibit biofilm formation. Using an NIH small compounds drug library approved for safe use in humans, we identified rifaximin (RFX), a semisynthetic, rifamycin family, nonsystemic antibiotic that inhibits alginate production and growth in P. aeruginosa Inhibition of alginate production was further analyzed using the uronic acid carbazole assay and a promoter reporter assay that measures the transcription of the alginate biosynthetic operon. Compared to TOB, RFX significantly reduced alginate production in laboratory and CF sputum isolates of P. aeruginosa In addition, RFX showed a narrow range of MICs when measured with multidrug-resistant bacterial species of clinical relevance, synergistic activities with TOB or amikacin against clinical isolates, as well as reduction toward in vitro preformed biofilms. In C57BL/6 mice, penetration of nebulized TOB into the lungs was shown at a higher level than that of RFX. Further, in vivo assessment using a DBA/2 mouse lung infection model found increased survival rates with a single-dose treatment of nebulized RFX and decreased P. aeruginosa PAO1 bioburden with a multiple-dose treatment of RFX plus TOB. In addition, mice treated with a single exposure to dimethyl sulfoxide (DMSO), a solvent that dissolves RFX, showed no apparent toxicity. In summary, RFX may be used to supplement TOB inhalation therapy to increase efficacy against P. aeruginosa biofilm infections.

Rifaximin Alters Intestinal Microbiota and Prevents Progression of Ankylosing Spondylitis in Mice

Recently, accumulating evidence has suggested that gut microbiota may be involved in the occurrence and development of ankylosing spondylitis (AS). It has been suggested that rifaximin have the ability to modulate the gut bacterial communities, prevent inflammatory response, and modulate gut barrier function. The goal of this work is to evaluate the protective effects of rifaximin in fighting AS and to elucidate the potential underlying mechanism. Rifaximin were administered to the proteoglycan (PG)-induced AS mice for 4 consecutive weeks. The disease severity was measured with the clinical and histological of arthritis and spondylitis. Intestinal histopathological, pro-inflammatory cytokine levels and the intestinal mucosal barrier were evaluated. Then, western blot was performed to explore the toll-like receptor 4 (TLR-4) signal transducer and NF-κB expression. Stool samples were collected to analyze the differences in the gut microbiota via next-generation sequencing of 16S rDNA. We found that rifaximin significantly reduced the severity of AS and resulted in down-regulation of inflammatory factors, such as TNF-α, IL-6, IL-17A, and IL-23. Meanwhile, rifaximin prevented ileum histological alterations, restored intestinal barrier function and inhibited TLR-4/NF-κB signaling pathway activation. Rifaximin also changed the gut microbiota composition with increased Bacteroidetes/Firmicutes phylum ratio, as well as selectively promoting some probiotic populations, including Lactobacillales. Our results suggest that rifaximin suppressed progression of AS and regulated gut microbiota in AS mice. Rifaximin might be useful as a novel treatment for AS.

Nuclear Receptors in the Pathogenesis and Management of Inflammatory Bowel Disease

Nuclear receptors (NRs) are ligand-dependent transcription factors that regulate the transcription of target genes. Previous epidemiological and genetic studies have documented the association of NRs with the risk of inflammatory bowel disease (IBD). Although the mechanisms of action of NRs in IBD have not been fully established, accumulating evidence has demonstrated that NRs play complicated roles in regulating intestinal immunity, mucosal barriers, and intestinal flora. As one of the first-line medications for the treatment of IBD, 5-aminosalicylic acid (5-ASA) activates peroxisome proliferator-activated receptor gamma (PPARγ) to attenuate colitis. The protective roles of rifaximin and rifampicin partly depend on promoting pregnane X receptor (PXR) expression. The aims of this review are to discuss the roles of several important NRs, such as PPARγ, PXR, vitamin D receptor (VDR), farnesoid X receptor (FXR), and RAR-related orphan receptor gammat (RORγt), in the pathogenesis of IBD and management strategies based on targeting these receptors.

Novel perspectives in the management of decompensated cirrhosis

The current approaches to the management of patients with decompensated cirrhosis are based on targeted strategies aimed at preventing or treating specific complications of the disease. The improved knowledge of the pathophysiological background of advanced cirrhosis, represented by a sustained systemic inflammation strictly linked to a circulatory dysfunction, provides a novel paradigm for the management of these patients, with the ambitious target of modifying the course of the disease by preventing the onset of complications and multiorgan failure; these interventions will eventually improve patients' quality of life, prolong survival and reduce health-care costs. Besides aetiological treatments, these goals could be achieved by persistently antagonizing key pathophysiological events, such as portal hypertension, abnormal bacterial translocation from the gut, liver damage, systemic inflammation, circulatory dysfunction and altered immunological responses. Interestingly, in addition to strategies based on new therapeutic agents, these targets can be tackled by employing drugs that are already used in patients with cirrhosis for different indications or in other clinical settings, including non-absorbable oral antibiotics, non-selective β-blockers, human albumin and statins. The scope of the present Review includes reporting updated information on the treatments that promise to influence the course of advanced cirrhosis and thus act as disease-modifying agents.

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

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

Fecal Microbiota Alterations Associated With Diarrhea-Predominant Irritable Bowel Syndrome

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

Rifaximin decreases virulence of Crohn's disease-associated Escherichia coli and epithelial inflammatory responses

Escherichia coli with an adherent and invasive pathotype (AIEC) is implicated in the pathogenesis of Crohn's disease (CD). Rifaximin improves symptoms in mild-to-moderate CD. It is unclear if this outcome is due to its effects on bacteria or intestinal epithelial inflammatory responses. We examined the effects of rifaximin on the growth and virulence of CD-associated E. coli and intestinal epithelial inflammatory responses. Seven well-characterized CD-associated E. coli strains (six AIEC, one non-AIEC; four rifaximin-resistant, three sensitive) were evaluated. We assessed the effects of rifaximin on CD-associated E. coli growth, adhesion to, and invasion of epithelial cells, virulence gene expression, motility, and survival in macrophages. Additionally, we determined the effects of rifaximin on intestinal epithelial inflammatory responses. In vitro rifaximin exerted a dose-dependent effect on the growth of sensitive strains but did not affect the growth of resistant strains. Rifaximin reduced adhesion, invasion, virulence gene expression and motility of CD-associated E. coli in a manner that was independent of its antimicrobial effect. Furthermore, rifaximin reduced IL-8 secretion from pregnane X receptor-expressing T84 colonic epithelial cells. The effect of rifaximin on adhesion was largely attributable to its action on bacteria, whereas decreases in invasion and cytokine secretion were due to its effect on the epithelium. In conclusion, our results show that rifaximin interferes with multiple steps implicated in host-AIEC interactions related to CD, including adhesion to, and invasion of epithelial cells, virulence gene expression, motility, and pro-inflammatory cytokine secretion. Further study is required to determine the relationship of these effects to clinical responses in CD patients.

Rifaximin in non-alcoholic steatohepatitis: An open-label pilot study

AIM

Gut microbial dysbiosis is implicated in the pathogenesis of non-alcoholic steatohepatitis (NASH). We investigated downstream effects of gut microbiota modulation on markers of hepatic inflammation, steatosis, and hepatic and peripheral insulin sensitivity in patients with NASH using rifaximin therapy.

METHODS

Patients with biopsy-proven NASH and elevated aminotransferase values were included in this open-label pilot study, all receiving 6 weeks rifaximin 400 mg twice daily, followed by a 6-week observation period. The primary endpoint was change in alanine aminotransferase (ALT) after 6 weeks of rifaximin. Secondary endpoints were change in hepatic lipid content and insulin sensitivity measured with a hyperinsulinemic-euglycemic clamp.

RESULTS

Fifteen patients (13 men and 2 women) with a median (range) age of 46 (32-63) years were included. Seven had diabetes on oral hypoglycemic medications and 8 had no diabetes. After 6 weeks of therapy, no differences were seen in ALT (55 [33-191] vs. 63 [41-218] IU/L, P = 0.41), peripheral glucose uptake (28.9 [19.4-48.3] to 25.5 [17.7-47.9] μmol/kg/min, P = 0.30), hepatic insulin sensitivity (35.2 [15.3-51.7]% vs. 30.0 [10.8-50.5]%, P = 0.47), or hepatic lipid content (21.6 [2.2-46.2]% vs. 24.8 [1.7-59.3]%, P = 0.59) before and after rifaximin treatment. After 12 weeks from baseline, serum ALT increased to 83 (30-217) IU/L, P = 0.02. There was a significant increase in the homeostasis model assessment-estimated insulin resistance index (P = 0.05). The urinary metabolic profile indicated a significant reduction in urinary hippurate with treatment, which reverted to baseline after cessation of rifaximin, although there was no consistent difference in relative abundance of fecal microbiota with treatment.

CONCLUSION

These data do not indicate a beneficial effect of rifaximin in patients with NASH.

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.

Eubiotic properties of rifaximin: Disruption of the traditional concepts in gut microbiota modulation

Antibiotics are usually prescribed to cure infections but they also have significant modulatory effects on the gut microbiota. Several alterations of the intestinal bacterial community have been reported during antibiotic treatment, including the reduction of beneficial bacteria as well as of microbial alpha-diversity. Although after the discontinuation of antibiotic therapies it has been observed a trend towards the restoration of the original condition, the new steady state is different from the previous one, as if antibiotics induced some kind of irreversible perturbation of the gut microbial community. The poorly absorbed antibiotic rifaximin seem to be different from the other antibiotics, because it exerts non-traditional effects additional to the bactericidal/bacteriostatic activity on the gut microbiota. Rifaximin is able to reduce bacterial virulence and translocation, has anti-inflammatory properties and has been demonstrated to positively modulate the gut microbial composition. Animal models, culture studies and metagenomic analyses have demonstrated an increase in Bifidobacterium, Faecalibacterium prausnitzii and Lactobacillus abundance after rifaximin treatment, probably consequent to the induction of bacterial resistance, with no major change in the overall gut microbiota composition. Antibiotics are therefore modulators of the symbiotic relationship between the host and the gut microbiota. Specific antibiotics, such as rifaximin, can also induce eubiotic changes in the intestinal ecosystem; this additional property may represent a therapeutic advantage in specific clinical settings.

Susceptibility to rifaximin and other antimicrobials of bacteria isolated in patients with acute gastrointestinal infections in Southeast Mexico

INTRODUCTION

Enteropathogenic bacteria isolated in Mexico City have shown a high rate of resistance to different antibiotics, with the exception of rifaximin (RIF). RIF is a nonabsorbable antibiotic that reaches high fecal concentrations (≈ 8,000μg/g). Susceptibility to antimicrobials can vary in different geographic regions.

AIM

To study the susceptibility to rifaximin and other antimicrobials of enteropathogenic bacteria isolated in patients with acute diarrhea in the southeastern region of Mexico.

MATERIAL AND METHODS

A total of 614 strains of bacteria isolated from patients with acute diarrhea from 4 cities in Southeast Mexico were analyzed. An antibiogram with the following antibiotics was created: ampicillin (AMP), trimethoprim/sulfamethoxazole (T-S), neomycin (NEO), furazolidone (FUR), ciprofloxacin (CIP), chloramphenicol (CHL), and fosfomycin (FOS), assessed through the agar diffusion method at the standard concentrations recommended by the Clinical and Laboratory Standards Institute (CLSI) and the American Society for Microbiology (ASM), and RIF, assessed through microdilution at 4 concentrations.

RESULTS

The bacteria were Escherichia coli (55%), as the majority, in all its pathogenic variants, Shigella (16.8%), Salmonella (15.3%), Aeromonas (7.8%), and less than 5% Campylobacter, Yersinia, Vibrio, and Plesiomonas. The accumulated overall susceptibility to RIF was 69.1, 90.8, 98.9, and 100% at concentrations of 100, 200, 400, and 800μg/ml, respectively. Overall susceptibility to other antibiotics was FOS 82.8%, CHL 76.8%, CIP 73.9%, FUR 64%, T-S 58.7%, NEO 55.8%, and AMP 23.8%. Susceptibility to RIF at 400 and 800μg was significantly greater than with the other antimicrobials (P<.001).

CONCLUSIONS

The data of the present study were similar to those of a previous study carried out in Mexico City: susceptibility to RIF in > 98% of the bacterial strains and a high frequency of resistance to several common antimicrobials.

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.

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 Possible Innovative Use of Bifidobacterium longum W11 in Association With Rifaximin: A New Horizon for Combined Approach?

GOALS

The aim of the study was to unequivocally demonstrate the nontransmissibility of the genes mediating the resistance of the strain Bifidobacterium longum W11 (LMG P-21586) to rifaximin.

BACKGROUND

Most antibiotic treatments can induce unfavorable side effects such as antibiotic-associated diarrhea, which is largely attributable to the disruption of the intestinal microbiota. The parallel intake of probiotic bacteria might reduce these events, even if with generally very poor results. In this regard, the use of antibiotic-resistant beneficial bacteria could represent a worthy strategy.

STUDY

Rifaximin was tested in parallel with rifampicin, rifapentine, and rifabutin, all rifamycin derivates, using 5 different concentrations. Susceptibility tests were performed by the disc diffusion method of Kirby-Bauer, and inhibition zones were measured after incubation at 37°C. B. longum BL03 was used as comparison. The B. longum W11 genome was sequenced on Illumina MiSeq with a 250 PE reads module. After mapping the reads with the reference bacterial genome, the alignment data were processed using FreeBayes software.

RESULTS

B. longum BL03 was inhibited by all antibiotics even at the lowest concentration. In contrast, the W11 strain was inhibited by rifampicin, rifabutin, and rifaximin only at the highest concentration (512 μg/mL). The genomic analysis showed a mutation into the chromosomal DNA. No transposable elements were found, and the genetic locus was not flanked by close mobile genetic elements.

CONCLUSIONS

B. longum W11 could be used in combined therapy with rifaximin, thus opening new focused frontiers in the probiotic era while preserving the necessary safety of use for consumers.

Rifaximin for the treatment of irritable bowel syndrome - a drug safety evaluation

INTRODUCTION

Irritable bowel syndrome is a functional gastrointestinal disorder with a multifactorial etiology. Alterations of intestinal motility and immunity, gut-brain interactions, as well as gut microbiota dysbiosis contribute to the development of irritable bowel syndrome. Therefore, gut microbiota modulation by non-absorbable antibiotics is a therapeutic option in patients with IBS.

AREAS COVERED

Published articles including patients with irritable bowel syndrome reporting data about rifaximin activity and safety have been searched throughout the literature and selected.

EXPERT OPINION

The optimal antibiotic molecule should be local-acting, long-acting and safe-acting. Rifaximin is a non-absorbable antibiotic with additional anti-inflammatory and gut microbiota-modulating activity. It is effective in inducing symptoms relief in patients with IBS, even after repeated treatment courses. Rifaximin-related side effects in patients with IBS are reported to be mild and infrequent; microbial resistance is rare and transient, due to the high local concentration of the drug and to the absence of horizontal transmission. Clostridium difficile infection is not usual in patients receiving rifaximin in absence of predisposing conditions such as hospitalization and immunosuppression, which are uncommon in patients affected by irritable bowel syndrome. Nevertheless rifaximin is an antibiotic active against Clostridium difficile infection. Rifaximin has limited metabolic interactions and is not expected to interfere with drug metabolism in patients with normal hepatic function. These properties make rifaximin a safe antibiotic for gut microbiota modulation in patients with IBS.

New and emerging therapies for the treatment of irritable bowel syndrome: an update for gastroenterologists

Irritable bowel syndrome is a functional bowel disorder with gastrointestinal symptoms (e.g. abdominal pain, straining, urgency, incomplete evacuation, nausea, and bloating) that occur alongside bowel function alterations (i.e. constipation, diarrhea, or both). Patients with irritable bowel syndrome may also experience comorbid anxiety and depression. Irritable bowel syndrome is common, with a prevalence estimated between 3% and 28%, affecting patient health and quality of life. Patients with moderate or severe irritable bowel syndrome generally seek medical care, whereas those with milder symptoms may choose self-management. Most patients with irritable bowel syndrome receive outpatient care, but irritable bowel syndrome-related hospitalizations do occur. The pathophysiology of irritable bowel syndrome is multifactorial (i.e. genetics, immune components, changes in the gut microbiota, disturbances in physiologic stress response systems, and psychosocial factors). Management of irritable bowel syndrome can include lifestyle changes, dietary interventions, counseling, psychologic medication, and agents that affect gastrointestinal motility. A number of therapies have emerged in recent years with clinical trial data demonstrating efficacy and safety for patients with irritable bowel syndrome, including agents that target gastrointestinal motility (i.e. linaclotide), gastrointestinal opioid receptors (i.e. asimadoline, eluxadoline), and gut microbiota (i.e. rifaximin). Linaclotide has been shown to significantly improve stool frequency and abdominal pain compared with placebo in constipation-predominant irritable bowel syndrome (number needed to treat, 5.1). Asimadoline shows efficacy in patients with moderate-to-severe irritable bowel syndrome-related pain. Rifaximin provided adequate relief of global irritable bowel syndrome symptoms versus placebo for a significantly greater percentage of patients with diarrhea-predominant irritable bowel syndrome (p < 0.001). Management that encompasses all aspects of irritable bowel syndrome (gastrointestinal symptoms) and comorbid psychologic symptoms (e.g. anxiety or depression) is important for improving overall patient health and well-being.

The Role of Antibiotics in Gut Microbiota Modulation: The Eubiotic Effects of Rifaximin

Antibiotics are mainly used in clinical practice for their activity against pathogens, but they also alter the composition of commensal gut microbial community. Rifaximin is a non-absorbable antibiotic with additional effects on the gut microbiota about which very little is known. It is still not clear to what extent rifaximin can be able to modulate gut microbiota composition and diversity in different clinical settings. Studies based on culture-dependent techniques revealed that rifaximin treatment promotes the growth of beneficial bacteria, such as Bifidobacteria and Lactobacilli. Accordingly, our metagenomic analysis carried out on patients with different gastrointestinal and liver diseases highlighted a significant increase in Lactobacilli after rifaximin treatment, persisting in the short time period. This result was independent of the disease background and was not accompanied by a significant alteration of the overall gut microbial ecology. This suggests that rifaximin can exert important eubiotic effects independently of the original disease, producing a favorable gut microbiota perturbation without changing its overall composition and diversity.

Rifaximin preserves intestinal microbiota balance in patients undergoing allogeneic stem cell transplantation

Intestinal dysbiosis has been associated with acute gastrointestinal GvHD and poor outcome following allogeneic stem cell transplantation (ASCT). To assess the effect of a switch in 2012 from ciprofloxacin/metronidazole to rifaximin for gut decontamination on intestinal microbiota composition and ASCT outcome, we retrospectively analyzed 394 patients receiving ASCT from September 2008 through June 2015. In 131 and 90 patients, respectively, urinary 3-indoxyl sulfate levels and intestinal enterococcal load were measured before conditioning and weekly within the first 28 days after ASCT. The use of rifaximin correlated with lower enterococcal positivity (6.9 vs 21.9%, P=0.05) and higher urinary 3-indoxyl sulfate concentrations (10.5 vs 4.6 μmoL/mmoL crea, P<0.001) after ASCT. Patients on rifaximin showed lower 1-year transplant-related mortality (P=0.04) and higher overall survival (P=0.008). Treatment of infectious complications with systemic antibiotics did not abrogate the beneficial effects of rifaximin on intestinal microbiota composition in the early course of ASCT and outcome. The data underscore the importance of maintaining a diverse population of symbiotic and mutualistic bacteria in the gut on ASCT outcome.

Microencapsulation of rifampicin for the prevention of endophthalmitis: In vitro release studies and antibacterial assessment

Rifampicin encapsulated microparticles were designed for intraocular injection after cataract surgery to prevent postoperative endophthalmitis. Microparticles were formulated by emulsification diffusion method using poly(lactic acid-co-glycolic acid) (PLGA) as polymer in order to propose a new form of rifampicin that overcome its limitations in intraocular delivery. Depending on processing formulation, different types of microparticles were prepared, characterized and evaluated by in vitro release studies. Two types of microparticles were selected to get a burst release of rifampicin, to reach minimal inhibitory concentrations to inhibit 90% of Staphylococcus epidermidis mainly involved in postoperative endophthalmitis, combined with a sustained release to maintain rifampicin concentration over 24h. The antibacterial activity and antiadhesive property on intraocular lenses were evaluated on S. epidermidis. Microparticles, with a rapid rifampicin release profile, showed an effect towards bacteria development similar to free rifampicin over 48h. However, slow-release profile microparticles exhibited a similar antibacterial effect during the first 24h, and were able to destroy all the S epidermidis in the medium after 30h. The association of the two formulations allowed obtaining interesting antibacterial profile. Moreover, rifampicin-loaded microparticles have shown a very efficient anti-adherent effect of S. epidermidis on intraocular lenses at 24h. These results propose rifampicin microparticles as suitable for antibioprophylaxis of the postoperative endophthalmitis.

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

BACKGROUND

Disruption of the gut microbiota through use of systemic antimicrobials or activation of the mucosal inflammatory response by pathogens can cause dysregulation of the intestinal mucosa.

AIM

To explore the mechanisms of action of rifaximin that may underlie its clinical benefits in travellers' diarrhoea (TD).

METHODS

A literature search was performed using the terms 'rifaximin' and 'L/105' in combination with the terms 'in vitro activity', 'diarrhea', 'microbiota' and 'gut flora'.

RESULTS

Rifaximin has been traditionally identified as a nonsystemic, broad-spectrum, bactericidal antibiotic. Evidence shows that the activity of rifaximin against enteropathogens in this setting is likely enhanced by its increased solubility in the presence of bile acids in the small intestine. Results of clinical studies show that although rifaximin is efficacious in TD, a clinical cure often occurs without apparent bacterial eradication and with minimal effect on the gut microbiota, suggesting an effect of rifaximin other than direct antibiotic activity.

CONCLUSIONS

Although definitive studies on the effect of rifaximin on the gut microbiota in large cohorts of healthy volunteers or patients have not been published, pre-clinical studies provide some insight. These studies have shown that rifaximin may have effects on both the pathogen and host, including direct effects on pathogenic bacteria (such as reducing the expression of bacterial virulence factors) and indirect effects on the host (such as inhibiting bacterial attachment and internalisation at the intestinal mucosa and reducing mucosal inflammation).

Review article: the potential mechanisms of action of rifaximin in the management of inflammatory bowel diseases

BACKGROUND

Gut microbiota dysbiosis contributes to the pathogenesis of inflammatory bowel diseases (IBD). Although the microbiota's role in IBD pathogenesis, specifically Crohn's disease (CD), provides a rationale for antibiotic treatment, antibiotic use in CD remains controversial. Rifaximin, traditionally identified as a nonsystemic bactericidal antibiotic, may be therapeutically beneficial for inducing CD remission.

AIM

To examine the role of rifaximin in the management of IBD and its potential mechanisms of action.

METHODS

A literature search using the following strategy: ('inflammatory bowel disease' OR 'Crohn's' OR 'ulcerative'), 'rifaximin' AND ('barrier' OR 'translocation' OR 'adhesion' OR 'internalization' OR 'pregnane X'), AND 'pregnane X' AND ('Crohn's' OR 'ulcerative colitis' OR 'inflammatory bowel disease').

RESULTS

In vitro data suggest rifaximin mediates changes in epithelial cell physiology and reduces bacterial attachment and internalisation. In experimental colitis models, rifaximin antagonised the effects of tumour necrosis factor-α on intestinal epithelial cells by activating pregnane X receptor, which inhibits nuclear factor-κB-mediated proinflammatory mediators and induces detoxification genes (e.g. multidrug resistance 1 and cytochrome P450 3A4). Rifaximin also inhibits bacterial translocation into the mesenteric lymph nodes.

CONCLUSION

Accumulating evidence suggests that mechanisms of action of rifaximin in IBD may not be limited to direct bactericidal activity; therefore, rifaximin could potentially be redefined as a gut environment modulator.

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

BACKGROUND

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

AIM

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

METHODS

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

RESULTS

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

CONCLUSION

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

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

Rifaximin, with its low systemic absorption, may represent a treatment of choice for irritable bowel syndrome (IBS), mainly due to its ability to act on IBS pathogenesis, through the influence on gut microbiota. The aim of the present study was to assess, by biomolecular tools, the rifaximin active modulation exerted on gut microbiota of non-constipated IBS patients. Fifteen non-constipated IBS subjects were treated with 550 mg rifaximin three times a day for 14 days. Stool samples were collected before starting the treatment, at the end of it, and after a 6-week washout period. Real-time polymerase chain reaction, denaturing gradient gel electrophoresis, and next-generation sequencing were applied to all the samples to verify and quantify possible microbial fluctuations. Rifaximin treatment did not affect the overall composition of the microbiota of the treated subjects, inducing fluctuations in few bacterial groups, balanced by the replacement of homologs or complementary bacterial groups. Rifaximin appeared to influence mainly potentially detrimental bacteria, such as Clostridium, but increasing the presence of some species, such as Faecalibacterium prausnitzii. A decrease in the Firmicutes/Bacteroidetes ratio after 14 days of treatment and bacterial profiles with higher biodiversity were observed during the follow-up compared to baseline. Rifaximin treatment, although effective on IBS symptom relief and normalization of lactulose breath test, did not induce dramatic shifts in the microbiota composition of the subjects, stimulating microbial reorganization in some populations toward a more diverse composition. It was not possible to speculate on differences of fecal microbiota modification between responders vs nonresponders and to correlate the quali-/quantitative modification of upper gastrointestinal microbiota and clinical response.

Effect of rifaximin on gut microbiota composition in advanced liver disease and its complications

Liver cirrhosis is a paradigm of intestinal dysbiosis. The qualitative and quantitative derangement of intestinal microbial community reported in cirrhotic patients seems to be strictly related with the impairment of liver function. A kind of gut microbial “fingerprint”, characterized by the reduced ratio of “good” to “potentially pathogenic” bacteria has recently been outlined, and is associated with the increase in Model for End-Stage Liver Disease and Child Pugh scores. Moreover, in patients presenting with cirrhosis complications such as spontaneous bacterial peritonitis (SBP), hepatic encephalopathy (HE), and, portal hypertension intestinal microbiota modifications or the isolation of bacteria deriving from the gut are commonly reported. Rifaximin is a non-absorbable antibiotic used in the management of several gastrointestinal diseases. Beyond bactericidal/bacteriostatic, immune-modulating and anti-inflammatory activity, a little is known about its interaction with gut microbial environment. Rifaximin has been demonstrated to exert beneficial effects on cognitive function in patients with HE, and also to prevent the development of SBP, to reduce endotoxemia and to improve hemodynamics in cirrhotics. These results are linked to a shift in gut microbes functionality, triggering the production of favorable metabolites. The low incidence of drug-related adverse events due to the small amount of circulating drug makes rifaximin a relatively safe antibiotic for the modulation of gut microbiota in advanced liver disease.

Therapeutic Effects and Mechanisms of Action of Rifaximin in Gastrointestinal Diseases

Emerging preclinical and clinic evidence described herein suggests that the mechanism of action of rifaximin is not restricted to direct antibacterial effects within the gastrointestinal tract. Data from this study were derived from general and clinical trial-specific PubMed searches of English-language articles on rifaximin available through December 3, 2014. Search terms included rifaximin alone and in combination (using the Boolean operation "AND") with travelers' diarrhea, hepatic encephalopathy, liver cirrhosis, irritable bowel syndrome, inflammatory bowel disease, and Crohn's disease. Rifaximin appears to reduce bacterial virulence and pathogenicity by inhibiting bacterial translocation across the gastrointestinal epithelial lining. Rifaximin was shown to decrease bacterial adherence to epithelial cells and subsequent internalization in a bacteria- and cell type-specific manner, without an alteration in bacterial counts, but with a down-regulation in epithelial proinflammatory cytokine expression. Rifaximin also appears to modulate gut-immune signaling. In animal models of inflammatory bowel disease, rifaximin produced therapeutic effects by activating the pregnane X receptor and thereby reducing levels of the proinflammatory transcription factor nuclear factor κB. Therefore, for a given disease state, rifaximin may act through several mechanisms of action to exert its therapeutic effects. Clinically, rifaximin 600 mg/d significantly reduced symptoms of travelers' diarrhea (eg, time to last unformed stool vs placebo [32.0 hours vs 65.5 hours, respectively; P=.001]). For the prevention of hepatic encephalopathy recurrence, data indicate that treating 4 patients with rifaximin 1100 mg/d for 6 months would prevent 1 episode of hepatic encephalopathy. For diarrhea-predominant irritable bowel syndrome, a significantly greater percentage (40.7%) of patients treated with rifaximin 1650 mg/d for 2 weeks experienced adequate global irritable bowel syndrome symptom relief vs placebo (31.7%; P<.001). Rifaximin may be best described as a gut microenvironment modulator with cytoprotection properties, and further studies are needed to determine whether these putative mechanisms of action play a direct role in clinical outcomes.

Profile of rifaximin and its potential in the treatment of irritable bowel syndrome

Irritable bowel syndrome (IBS) is a chronic functional gastrointestinal disorder characterized by recurrent abdominal pain and abnormal bowel patterns. Alteration in gut flora, visceral hypersensitivity, and abnormal bowel motility are among numerous factors in the complex pathophysiology of IBS. Antibiotics have been used adjunctively to treat IBS for many years but are associated with various systemic side effects. Rifaximin is a nonabsorbable, broad-spectrum antimicrobial that inhibits bacterial RNA synthesis by binding the β-subunit of microbial RNA polymerase. It targets the gastrointestinal tract and works by reducing the quantity of gas-producing bacteria and altering the predominant species of bacteria present. In vivo animal studies suggest additional beneficial mechanisms of rifaximin, including reducing mucosal inflammation and visceral hypersensitivity. Clinical studies have demonstrated that rifaximin improves symptoms associated with IBS, such as bloating, flatulence, stool consistency, and abdominal pain, and has a side-effect profile similar to placebo. Although additional investigation into optimal dosing, treatment duration, and potential resistance is required, rifaximin presents as a safe and beneficial addition to the current management options for IBS.

Rifaximin for the treatment of diarrhoea-predominant irritable bowel syndrome

INTRODUCTION

Rifaximin is a non-absorbable, semisynthetic antibiotic that acts as an inhibitor of bacterial RNA synthesis, with a broad spectrum of antibacterial activity. Due to its poor absorption, rifaximin has an increased exposure to the intestine, thus it is suitable for the treatment of many gastrointestinal (GI) diseases. In irritable bowel syndrome (IBS) pathogenesis, gut microbiota impairment may play a major role. The possibility of modulating intestinal bacteria using antibiotics, in particular, rifaximin, has been demonstrated to improve IBS symptoms in non-constipation subtypes of IBS.

AREAS COVERED

We reviewed the use of rifaximin in diarrhoea-predominant IBS, focusing on its pharmacokinetic characteristics, its absorption in GI disease, its lack of interaction with other drugs and its new extended release formulation.

EXPERT OPINION

Rifaximin, with its low systemic absorption and no clinically significant interactions with other drugs, may represent a treatment of choice for IBS, mainly due to its ability to act on IBS pathogenesis, through the modulation of gut microbiota. Further studies to analyse the effect of rifaximin treatment on the composition of faecal microbiota are warranted. In particular, they need to evaluate whether resistant bacterial strains are selected and whether they are still present in the faecal sample even a long time after therapy.

Targeting of rifamycin SV to the colon for treatment of travelers' diarrhea: a randomized, double-blind, placebo-controlled phase 3 study

BACKGROUND

Rifamycin SV is under development for treatment of travelers' diarrhea (TD) in a new oral formulation, Rifamycin SV MMX (RIF-MMX; Santarus Inc., San Diego, CA, USA), which targets its delivery to the colon, making it a unique rifamycin drug.

METHODS

This was a randomized, double-blind, phase 3 study of adult travelers to Mexico or Guatemala experiencing acute diarrhea. A total of 264 patients received RIF-MMX (2 × 200 mg twice daily for 3 days, n = 199) or placebo (n = 65) in a 3 : 1 ratio. The primary endpoint was the length of time between the administration of first dose of study drug and passage of the last unformed stool (TLUS; after which clinical cure was declared). Other endpoints included eradication of pathogens from the stools, pathogen minimum inhibitory concentration (MIC), and adverse events (AEs).

RESULTS

TLUS was significantly shorter in the RIF-MMX group (median: 46.0 hours) compared with placebo (median: 68.0 hours; p = 0.0008) and a larger percentage of RIF-MMX treated patients (81.4%) achieved clinical cure compared with placebo patients (56.9%). TLUS was significantly shorter in the subgroups of patients with enteroaggregative, enterotoxigenic, or diffusely adherent Escherichia coli infections (p = 0.0035) with nonsignificant activity against invasive bacteria (p = 0.3804). Overall pathogen eradication rates were numerically higher in the RIF-MMX group (67.0%) compared with placebo (54.8%) but the difference did not reach significance (p = 0.0836). In vitro resistance to rifamycin SV was observed in some bacteria remaining after treatment of patients with RIF-MMX but was not associated with lower efficacy in them. AEs appeared to be more frequent with placebo (38.5%) than with RIF-MMX (29.6%).

CONCLUSIONS

RIF-MMX shortened the duration of TD in patients with a broad range of pathogens and was well tolerated. The unique pharmacokinetic properties of the drug offer evidence that TD pathogens work at the level of the colon.

Rifaximin: beyond the traditional antibiotic activity

Rifaximin is a non-systemic oral antibiotic derived from rifampin and characterized by a broad spectrum of antibacterial activity against Gram-positive and -negative, aerobic and anaerobic bacteria. Rifaximin was first approved in Italy in 1987 and afterwards in many other worldwide countries for the treatment of several gastrointestinal diseases. This review updates the pharmacology and pharmacodynamics of rifaximin highlighting the different actions, beyond its antibacterial activity, such as alteration of virulence, prevention of gut mucosal adherence and bacterial translocation. Moreover, rifaximin exerts some anti-inflammatory effects with only a minimal effect on the overall composition of the gut microbiota. All these properties make rifaximin a good candidate to treat various gastrointestinal diseases.

Review article: evidence for the role of gut microbiota in irritable bowel syndrome and its potential influence on therapeutic targets

BACKGROUND

Irritable bowel syndrome (IBS) is a prevalent gastrointestinal disease with a substantial social and economic burden. Treatment options remain limited and research on the aetiology and pathophysiology of this multifactorial disease is ongoing.

AIM

To discuss the potential role of gut microbiota in the pathophysiology of IBS and to identify possible interactions with pathophysiologic targets in IBS.

METHODS

Articles were identified via a PubMed database search ['irritable bowel syndrome' AND (anti-bacterial OR antibiotic OR flora OR microbiota OR microflora OR probiotic)]. English-language articles were screened for relevance. Full review of publications for the relevant studies was conducted, including additional publications that were identified from individual article reference lists.

RESULTS

The role of gut microbiota in IBS is supported by varying lines of evidence from animal and human studies. For example, post-infectious IBS in humans is well documented. In addition, certain probiotics and nonsystemic antibiotics appear to be efficacious in the treatment of IBS. Mechanisms involved in improving IBS symptoms likely go beyond mere changes in the composition of the gut microbiota, and accumulating animal data support the interplay of microbiota with other IBS targets, such as the gut-brain axis, visceral hypersensitivity, mucosal inflammation and motility.

CONCLUSION

The role of the gut microbiota is still being elucidated; however, it appears to be one of several important factors that contributes to the aetiology and pathophysiology of the irritable bowel syndrome.

Clinical update for the diagnosis and treatment of Clostridium difficile infection

Clostridium difficile infection (CDI) presents a rapidly evolving challenge in the battle against hospital-acquired infections. Recent advances in CDI diagnosis and management include rapid changes in diagnostic approach with the introduction of newer tests, such as detection of glutamate dehydrogenase in stool and polymerase chain reaction to detect the gene for toxin production, which will soon revolutionize the diagnostic approach to CDI. New medications and multiple medical society guidelines have introduced changing concepts in the definitions of severity of CDI and the choice of therapeutic agents, while rapid expansion of data on the efficacy of fecal microbiota transplantation heralds a revolutionary change in the management of patients suffering multiple relapses of CDI. Through a comprehensive review of current medical literature, this article aims to offer an intensive review of the current state of CDI diagnosis, discuss the strengths and limitations of available laboratory tests, compare both current and future treatments options and offer recommendations for best practice strategies.