High dosage rifaximin for the treatment of small intestinal bacterial overgrowth

The prevalence of overgrowth by aerobic bacteria in the small intestine by small bowel culture: relationship with irritable bowel syndrome

OBJECTIVES

Many studies have linked irritable bowel syndrome (IBS) with small intestinal bacterial overgrowth (SIBO), although they have done so on a qualitative basis using breath tests even though quantitative cultures are the hallmark of diagnosis. The purpose of this study was to underscore the frequency of SIBO in a large number of Greeks necessitating upper gastrointestinal (GI) tract endoscopy by using quantitative microbiological assessment of the duodenal aspirate.

METHODS

Consecutive subjects presenting for upper GI endoscopy were eligible to participate. Quantitative culture of aspirates sampled from the third part of the duodenum during upper GI tract endoscopy was conducted under aerobic conditions. IBS was defined by Rome II criteria.

RESULTS

Among 320 subjects enrolled, SIBO was diagnosed in 62 (19.4%); 42 of 62 had IBS (67.7%). SIBO was found in 37.5% of IBS sufferers. SIBO was found in 60% of IBS patients with predominant diarrhea compared with 27.3% without diarrhea (P = 0.004). Escherichia coli, Enterococcus spp and Klebsiella pneumoniae were the most common isolates within patients with SIBO. A step-wise logistic regression analysis revealed that IBS, history of type 2 diabetes mellitus and intake of proton pump inhibitors were independently and positively linked with SIBO; gastritis was protective against SIBO.

CONCLUSIONS

Using culture of the small bowel, SIBO by aerobe bacteria is independently linked with IBS. These results reinforce results of clinical trials evidencing a therapeutic role of non-absorbable antibiotics for the management of IBS symptoms.

Rifaximin-extended intestinal release induces remission in patients with moderately active Crohn's disease

BACKGROUND & AIMS

Bacteria might be involved in the development and persistence of inflammation in patients with Crohn's disease (CD), and antibiotics could be used in therapy. We performed a clinical phase 2 trial to determine whether a gastroresistant formulation of rifaximin (extended intestinal release [EIR]) induced remission in patients with moderately active CD.

METHODS

We performed a multicenter, randomized, double-blind trial of the efficacy and safety of 400, 800, and 1200 mg rifaximin-EIR, given twice daily to 402 patients with moderately active CD for 12 weeks. Data from patients given rifaximin-EIR were compared with those from individuals given placebo, and collected during a 12-week follow-up period. The primary end point was remission (Crohn's Disease Activity Index <150) at the end of the treatment period.

RESULTS

At the end of the 12-week treatment period, 62% of patients who received the 800-mg dosage of rifaximin-EIR (61 of 98) were in remission, compared with 43% of patients who received placebo (43 of 101) (P = .005). A difference was maintained throughout the 12-week follow-up period (45% [40 of 89] vs 29% [28 of 98]; P = .02). Remission was achieved by 54% (56 of 104) and 47% (47 of 99) of the patients given the 400-mg and 1200-mg dosages of rifaximin-EIR, respectively; these rates did not differ from those of placebo. Patients given the 400-mg and 800-mg dosages of rifaximin-EIR had low rates of withdrawal from the study because of adverse events; rates were significantly higher among patients given the 1200-mg dosage (16% [16 of 99]).

CONCLUSIONS

Administration of 800 mg rifaximin-EIR twice daily for 12 weeks induced remission with few adverse events in patients with moderately active CD.

Rifaximin for the treatment of irritable bowel syndrome

INTRODUCTION

Few therapeutic options are available for irritable bowel syndrome (IBS). Lubiprostone is approved by the FDA for IBS with constipation, and alosetron in IBS with diarrhea (IBS-D). It has been proposed that alterations in the bowel microflora may play a role in the pathophysiology of IBS, and that modulation of the microflora holds therapeutic potential. Rifaximin is a nonsystemic antibiotic that has shown efficacy in IBS.

AREAS COVERED

This narrative review covers the treatment options available for IBS-D and focuses on rifaximin. Rifaximin pharmacodynamics, clinical pharmacology and results of clinical studies from proof of concept to the latest Phase III and retreatment studies in IBS are summarized. Challenges to rifaximin use, safety issues and regulatory data are also discussed.

EXPERT OPINION

The evidence supports rifaximin as an emerging treatment for IBS. Strategies for appropriate patient selection need to be further developed, and continued efficacy of rifaximin over repeated treatment courses needs to be better characterized.

A review of rifaximin and bacterial overgrowth in poorly responsive celiac disease

A proportion of patients with celiac disease have a poor response to a gluten-free diet, which may be due to small-intestinal bacterial overgrowth (SIBO). Treatment with rifaximin is often used in the clinical setting, but there is limited literature to support this practice. In addition, challenges in the diagnosis of SIBO confound response interpretation. Our recent placebo-controlled trial did not demonstrate any improvement in gastrointestinal symptoms after treatment with rifaximin and casts doubt on the utility of lactulose-hydrogen breath testing for SIBO in this population.

Divergent rifamycin susceptibilities of Clostridium difficile strains in Canada and Italy and predictive accuracy of rifampin Etest for rifamycin resistance

We tested the activities of rifampin (RIF) and rifaximin (RFX) against 180 Clostridium difficile clinical isolates selected from Canadian and Italian culture collections. MICs were determined by CLSI agar dilution for both drugs and by Etest for RIF. Sixteen of 85 Italian isolates (18.8%) showed high-level resistance to both rifamycins (MICs, >16 μg/ml), compared to 2 of 95 (2.1%) Canadian isolates. Two new rpoB mutations were identified in rifamycin-resistant isolates. RIF susceptibility by Etest correlated completely with susceptibility to both rifamycins determined by agar dilution.

Double-blind randomized controlled trial of rifaximin for persistent symptoms in patients with celiac disease

BACKGROUND

Small intestinal bacterial overgrowth (SIBO) is one cause of a poor response to a gluten-free diet (GFD) and persistent symptoms in celiac disease. Rifaximin has been reported to improve symptoms in non-controlled trials.

AIMS

To determine the effect of rifaximin on gastrointestinal symptoms and lactulose-hydrogen breath tests in patients with poorly responsive celiac disease.

METHODS

A single-center, double-blind, randomized, controlled trial of patients with biopsy-proven celiac disease and persistent gastrointestinal symptoms despite a GFD was conducted. Patients were randomized to placebo (n = 25) or rifaximin (n = 25) 1,200 mg daily for 10 days. They completed the Gastrointestinal Symptom Rating Scale (GSRS) and underwent lactulose-hydrogen breath tests at weeks 0, 2, and 12. An abnormal breath test was defined as: (1) a rise in hydrogen of ≥20 parts per million (ppm) within 100 min, or (2) two peaks ≥20 ppm over baseline.

RESULTS

GSRS scores were unaffected by treatment with rifaximin, regardless of baseline breath tests. In a multivariable regression model, the duration of patients' gastrointestinal symptoms significantly predicted their overall GSRS scores (estimate 0.029, p < 0.006). According to criteria 1 and 2, respectively, SIBO was present in 55 and 8% of patients at baseline, intermittently present in 28 and 20% given placebo, and 28 and 12% given rifaximin. There was no difference in the prevalence of SIBO between placebo and treatment groups at weeks 2 and 12.

CONCLUSIONS

Rifaximin does not improve patients' reporting of gastrointestinal symptoms and hydrogen breath tests do not reliably identify who will respond to antibiotic therapy.

Biologic properties and clinical uses of rifaximin

INTRODUCTION

Rifaximin is increasingly being used to treat acute and chronic gastrointestinal infections and disorders. The drug exerts its beneficial effect through a variety of gut-selective mechanisms involving the host intestinal microbiota.

AREAS COVERED

Abstracts of all publications listed in PubMed on the topic of rifaximin are reviewed to determine their potential value in the understanding of mechanisms of rifaximin activity. The author's extensive file on the drug is also used in the review.

EXPERT OPINION

Rifaximin inhibits a broad spectrum of bacteria in the bile-rich small bowel and susceptible bacteria in the aqueous colon, and alters microbial virulence and epithelial cell function. The different mechanisms of action of rifaximin potentially explain the use of the drug in widely varied diseases and syndromes.

High-dose rifaximin treatment alleviates global symptoms of irritable bowel syndrome

Background:

To evaluate the efficacy of rifaximin for reduction of gastrointestinal symptoms in patients with irritable bowel syndrome (IBS).

Methods:

Medical records were identified for consecutive patients diagnosed with IBS according to Rome III criteria, who had abnormal lactulose breath test results and had received rifaximin 1200 mg/day for 10 days. The efficacy of rifaximin for reducing gastrointestinal symptoms and for eradicating small intestinal bacterial overgrowth was ascertained in these patients. In addition, these endpoints were examined in patients who were initially unresponsive to rifaximin 1200 mg/day and received subsequent rifaximin 2400 mg/day.

Results:

Patients who received rifaximin 1200 mg/day (n = 162) experienced a mean improvement of 52% in global IBS symptoms at the end of rifaximin treatment. Similarly, initially unresponsive patients who received additional rifaximin 2400 mg/day (n = 81) experienced a 53% mean improvement in global IBS symptoms. Forty-nine percent of patients who received initial rifaximin and 47% of patients who received high-dose rifaximin achieved ≥50% global symptom improvement during at least one follow-up visit. Normalization of lactulose breath test results was only apparent in some patients who received high-dose rifaximin. Rifaximin was well tolerated.

Conclusion:

Rifaximin 1200 mg/day for 10 days reduced gastrointestinal symptoms in patients with IBS. Patients with incomplete symptom resolution may respond to increased doses of rifaximin.

Double-blind, placebo-controlled antibiotic treatment study of small intestinal bacterial overgrowth in children with chronic abdominal pain

BACKGROUND AND OBJECTIVES

Chronic abdominal pain (CAP) in children may be a precursor to irritable bowel syndrome (IBS) in adults. The prevalence of abnormal lactulose breath tests (LBT) suggesting small intestinal bacterial overgrowth (SIBO) has been reported as 91% in children with CAP and 35% in healthy controls. In addition, patients with IBS with SIBO who responded to nonabsorbable antibiotic treatment with normalization of LBT reported 75% global improvement in symptoms. The aim of the study was to test whether treatment with a nonabsorbable antibiotic may reduce symptoms in children with CAP.

METHODS

Seventy-five children ages 8 to 18 years with CAP based on Rome II criteria were enrolled. Subjects underwent baseline LBT and completed symptom-based questionnaires. They were then randomized in a 2:1, double-blind fashion to receive a 10-day course of 550 mg of rifaximin or placebo 3 times per day (t.i.d.). LBT and questionnaires were repeated 2 weeks after treatment.

RESULTS

Forty-nine children received rifaximin and 26 received placebo. There were no differences in demographics between groups. Ninety-four percent who received rifaximin and 92% who received placebo had abnormal baseline LBT, suggesting SIBO (not significant [NS]). There was no significant difference in symptom improvement between groups; however, only 20% of children treated with rifaximin achieved a normalized repeat LBT, demonstrating successful treatment of SIBO.

CONCLUSIONS

Similar to adults with IBS, the prevalence of abnormal LBT suggesting SIBO in children with CAP is high; however, treatment with 10 days of rifaximin has low efficacy in normalizing LBT in this group. Additional studies are needed to determine whether a treatment approach with higher efficacy would lead to improvement in children with CAP.

Diagnosis and pharmacological management of small intestinal bacterial overgrowth in children with intestinal failure

The present article provides a general overview of the possible diagnostic procedures available for the management of small intestinal bacterial overgrowth in pediatric patients with intestinal failure. The focus is to address current diagnostic tools and understand their associated advantages and disadvantages based on a literature search. Culture of small intestinal aspirates, noninvasive breath tests and an emerging interest in quantitative bacterial DNA fingerprinting are discussed. Proper management is critical for preventing the recurrence of small intestinal bacterial overgrowth and its related complications. Antibiotic prophylaxis is one approach to the treatment of bacterial overgrowth in intestinal failure patients. Although treatment trials can be challenging in such a vulnerable population, more investigative clinical studies examining early diagnosis, more effective control of recurrence and the prevention of associated complications must be conducted.

Irritable bowel syndrome and small intestinal bacterial overgrowth

In the last 3 decades, there has been a growing appreciation for the role of gut bacteria in gastrointestinal disease. Although inflammatory bowel disease and peptic ulcer disease have established a role for gut bacteria for more than 20 years, there is now increasing evidence that intestinal bacteria may play a role in irritable bowel syndrome as well. In this review, the current evidence for bacteria in irritable bowel syndrome will be examined.

Clinical trial: the combination of rifaximin with partially hydrolysed guar gum is more effective than rifaximin alone in eradicating small intestinal bacterial overgrowth

BACKGROUND

Abnormal intestinal clearance is involved in the pathogenesis of small intestinal bacterial overgrowth (SIBO). It is known that partially hydrolysed guar gum affects intestinal motility. Eradication therapy of SIBO is based on antibiotic treatment: no data are available on the role of fibre supplementation in eradicating SIBO.

AIM

To assess whether the combination of partially hydrolysed guar gum and rifaximin is more effective than rifaximin alone in the treatment of SIBO.

METHODS

A 50 g-glucose breath test was given to 500 consecutive patients. Patients with a positive glucose breath test and predisposing conditions to SIBO entered into the study, and were randomized to receive rifaximin 1200 mg/day or rifaximin 1200 mg/day plus partially hydrolysed guar gum 5 g/day for 10 days. Patients completed a symptom questionnaire and glucose breath test both in basal condition and 1 month after withdrawal of therapy.

RESULTS

Seventy-seven patients had SIBO. Eradication rate of SIBO was 62.1% in the rifaximin group (both on per-protocol and intention-to-treat analyses), and 87.1% (per-protocol, P=0.017) and 85.0% (intention-to-treat, P=0.036) in the rifaximin-plus-partially hydrolysed guar gum group. Clinical improvement was observed in 86.9% and 91.1% of eradicated cases in rifaximin and rifaximin-plus-partially hydrolysed guar gum groups respectively (P=0.677).

CONCLUSION

The combination of rifaximin with partially hydrolysed guar gum seems to be more useful in eradicating SIBO compared with rifaximin alone.

Rifaximin diminishes neutropenia following potentially lethal whole-body radiation

Terrorist attacks involving radiological or nuclear weapons are a substantial geopolitical concern, given that large populations could be exposed to potentially lethal doses of radiation. Because of this, evaluating potential countermeasures against radiation-induced mortality is critical. Gut microflora are the most common source of systemic infection following exposure to lethal doses of whole-body radiation, suggesting that prophylactic antibiotic therapy may reduce mortality after radiation exposure. The chemical stability, easy administration and favorable tolerability profile of the non-systemic antibiotic, rifaximin, make it an ideal potential candidate for use as a countermeasure. This study evaluated the use of rifaximin as a countermeasure against low-to-intermediate-dose whole-body radiation in rodents. Female Wistar rats (8 weeks old) were irradiated with 550 cGy to the whole body and were evaluated for 30 d. Animals received methylcellulose, neomycin (179 mg/kg/d) or variably dosed rifaximin (150-2000 mg/kg/d) one hour after irradiation and daily throughout the study period. Clinical assessments (e.g. body weight) were made daily. On postirradiation day 30, blood samples were collected and a complete blood cell count was performed. Animals receiving high doses of rifaximin (i.e. 1000 or 2000 mg/kg/d) had a greater increase in weight from the day of irradiation to postirradiation day 30 compared with animals that received placebo or neomycin. For animals with an increase in average body weight from irradiation day within 80-110% of the group average, methylcellulose rendered an absolute neutrophil count (ANC) of 211, neomycin rendered an ANC of 334, rifaximin 300 mg/kg/d rendered an ANC of 582 and rifaximin 1000 mg/kg/d rendered an ANC of 854 (P = 0.05 for group comparison). Exposure to rifaximin after near-lethal whole-body radiation resulted in diminished levels of neutropenia.

Rifaximin therapy for metronidazole-unresponsive Clostridium difficile infection: a prospective pilot trial

BACKGROUND

Clostridium difficile infection (CDI) is a recent epidemic in the United States, particularly in the hospital setting. Oral metronidazole is standard therapy for C. difficile infection, but resistance to metronidazole is becoming a clinical challenge.

METHODS

We evaluated the efficacy of the nonsystemic oral antibiotic rifaximin for the treatment of metronidazole-resistant C. difficile infection. Twenty-five patients with C. difficile infection were enrolled in the study. All had mild-to-moderate C. difficile infection (5-10 bowel movements a day without sepsis) unresponsive to metronidazole (i.e. stools positive for toxins A and B after oral metronidazole 500 mg three times daily [t.i.d.] for 5 days). After discontinuation of metronidazole, rifaximin 400 mg t.i.d. for 14 days was prescribed. Patients were followed for 56 days and stool was tested for C. difficile using polymerase chain reaction (PCR) to assess the effect of treatment. A negative PCR test result was interpreted as a favorable response to rifaximin.

RESULTS

Sixteen of 22 patients (73%) were eligible for study inclusion and completed rifaximin therapy experienced eradication of infection (stool negative for C. difficile) immediately after rifaximin therapy and 56 days post-treatment. Three patients (12%) discontinued therapy because of abdominal distention. Rifaximin was generally well tolerated.

CONCLUSIONS

In conclusion, rifaximin may be considered for treatment of mild-to-moderate C. difficile infection that is resistant to metronidazole. Larger randomized trials are needed to confirm these positive findings.

Small intestinal bacterial overgrowth syndrome

Human intestinal microbiota create a complex polymicrobial ecology. This is characterised by its high population density, wide diversity and complexity of interaction. Any dysbalance of this complex intestinal microbiome, both qualitative and quantitative, might have serious health consequence for a macro-organism, including small intestinal bacterial overgrowth syndrome (SIBO). SIBO is defined as an increase in the number and/or alteration in the type of bacteria in the upper gastrointestinal tract. There are several endogenous defence mechanisms for preventing bacterial overgrowth: gastric acid secretion, intestinal motility, intact ileo-caecal valve, immunoglobulins within intestinal secretion and bacteriostatic properties of pancreatic and biliary secretion. Aetiology of SIBO is usually complex, associated with disorders of protective antibacterial mechanisms (e.g. achlorhydria, pancreatic exocrine insufficiency, immunodeficiency syndromes), anatomical abnormalities (e.g. small intestinal obstruction, diverticula, fistulae, surgical blind loop, previous ileo-caecal resections) and/or motility disorders (e.g. scleroderma, autonomic neuropathy in diabetes mellitus, post-radiation enteropathy, small intestinal pseudo-obstruction). In some patients more than one factor may be involved. Symptoms related to SIBO are bloating, diarrhoea, malabsorption, weight loss and malnutrition. The gold standard for diagnosing SIBO is still microbial investigation of jejunal aspirates. Non-invasive hydrogen and methane breath tests are most commonly used for the diagnosis of SIBO using glucose or lactulose. Therapy for SIBO must be complex, addressing all causes, symptoms and complications, and fully individualised. It should include treatment of the underlying disease, nutritional support and cyclical gastro-intestinal selective antibiotics. Prognosis is usually serious, determined mostly by the underlying disease that led to SIBO.

Rifaximin: a unique gastrointestinal-selective antibiotic for enteric diseases

PURPOSE OF REVIEW

Rifaximin is gaining attention for its potential activity in a multitude of gastrointestinal diseases. We review the unique pharmaceutical properties of this antibiotic and the published evidence in the literature regarding the use of rifaximin for different gastrointestinal disorders.

RECENT FINDINGS

Rifaximin is a gastrointestinal-selective antibiotic with a broad spectrum of antimicrobial activity, an excellent safety profile, minimal drug interactions, and negligible impact on the intestinal microbiome. Rifaximin is currently approved in the United States for the treatment of travelers' diarrhea caused by noninvasive diarrheagenic Escherichia coli and is approved in more than 30 other countries for a variety of gastrointestinal disorders. Considerable research with this medication has been conducted for the treatment and prevention of travelers' diarrhea, the treatment of portal systemic encephalopathy, Clostridium difficile infection, small bowel intestinal overgrowth, irritable bowel syndrome, inflammatory bowel disease, pouchitis, and colonic diverticular disease.

SUMMARY

Rifaximin is effective for the treatment of travelers' diarrhea and can be considered as the treatment of choice for uncomplicated travelers' diarrhea. When invasive travelers' diarrhea pathogens are suspected, an alternative antibiotic should be administered. Rifaximin appears promising as a chemoprophylaxis for travelers' diarrhea and as a treatment of portal systemic encephalopathy. This antibiotic may be effective for other gastrointestinal diseases, but more well designed clinical studies are needed to confirm its efficacy for these off-label indications. Future studies will determine whether the development of significant bacterial resistance will limit rifaximin use.

A randomized, double-blind, placebo-controlled trial of rifaximin, a nonabsorbable antibiotic, in the treatment of tropical enteropathy

OBJECTIVES

Tropical enteropathy is characterized by an increased urinary lactulose-to-mannitol (L:M) ratio on a site-specific sugar absorption test and is associated with increased intestinal permeability and decreased nutrient absorptive capacity. The etiology of tropical enteropathy is postulated to be intestinal bacterial overgrowth. This study tested the hypothesis that treatment with a nonabsorbable, broad-spectrum antibiotic, rifaximin, reduces the L:M ratio in rural Malawian children, among whom tropical enteropathy is common.

METHODS

All children aged 3-5 years from one village were enrolled in a randomized, double-blind, placebo-controlled trial of treatment with rifaximin for 7 days. The L:M ratio was measured before and after treatment, and the change in the L:M ratio was the primary outcome. Secondary outcomes were changes in the urinary sucrose-to-lactulose (SUC:L) and sucralose-to-lactulose (SCL:L) ratios, as well as changes in the fractions of each test sugar recovered in the urine.

RESULTS

A total of 144 children participated in this study, of whom 76% had an elevated L:M ratio on enrollment (L:M > or = 0.10). Children who received rifaximin did not show an improvement in their L:M ratio compared with those who received placebo (-0.01+/-0.12 vs. 0.02+/-0.16, respectively, P=0.51, mean+/-s.d.), nor were there significant differences between the two groups in excretion of lactulose, mannitol, sucralose, or sucrose, or in the SUC:L and SCL:L ratios.

CONCLUSIONS

Rifaximin had no effect on the tropical enteropathy of 3-5-year-old Malawian children, suggesting that small-bowel bacterial overgrowth is not an important etiological factor in this condition.

Rifaximin pharmacology and clinical implications

Rifaximin is a semisynthetic, rifamycin-based non-systemic antibiotic, with a low gastrointestinal absorption and a good antibacterial activity. The antibacterial action covers Gram-positive and Gram-negative organisms, both aerobes and anaerobes. Its antimicrobial action is based on its property to bind to the beta-subunit of bacterial DNA-dependent RNA polymerase inhibiting, thereby, the bacterial RNA synthesis. Rifaximin contributes to restore gut microflora imbalance, becoming an important therapeutic agent in several organic and functional gastrointestinal diseases such as hepatic encephalopathy, small intestine bacterial overgrowth, inflammatory bowel disease and colonic diverticular disease. This antibiotic has the advantage of low microbial resistance and few systemic adverse events and is safe in all patient populations, including young children.

Review of rifaximin as treatment for SIBO and IBS

BACKGROUND

Rifaximin is a broad-range, gastrointestinal-specific antibiotic that demonstrates no clinically relevant bacterial resistance. Therefore, rifaximin may be useful in the treatment of gastrointestinal disorders associated with altered bacterial flora, including irritable bowel syndrome (IBS) and small intestinal bacterial overgrowth (SIBO).

OBJECTIVE

To review rifaximin for treatment of IBS and SIBO.

METHODS

Review of rifaximin clinical trials.

RESULTS/CONCLUSION

Rifaximin improved global symptoms in 33 - 92% of patients and eradicated SIBO in up to 84% of patients with IBS, with results sustained up to 10 weeks post-treatment. Rifaximin caused a lower number of adverse events compared with metronidazole or levofloxacin and may have a more favorable adverse event profile than systemic antibiotics, without clinically relevant antibiotic resistance.

Review article: Small intestinal bacterial overgrowth, bile acid malabsorption and gluten intolerance as possible causes of chronic watery diarrhoea

BACKGROUND

Chronic watery diarrhoea is one of the most common symptoms prompting GI evaluation. Recently, new diagnostic considerations have emerged as possible factors in chronic diarrhoea.

AIM

To review available data regarding diagnosis and treatment of chronic diarrhoea with an emphasis on bacterial overgrowth and bile acid malabsorption.

METHODS

A systematic search of the English language literature of chronic diarrhoea was performed focused on three possible aetiologies of diarrhoea: small intestinal bacterial overgrowth (SIBO), idiopathic bile salt malabsorption (IBAM), gluten responsive enteropathy.

RESULTS

Recent studies suggest that SIBO and bile acid malabsorption may have been underestimated as possible causes of chronic watery diarrhoea. Gluten intolerance with negative coeliac serology is a contentious possible cause of watery diarrhoea, but requires further research before acceptance as an entity.

CONCLUSION

In patients with otherwise unexplained chronic watery diarrhoea, small intestinal bacterial overgrowth and bile salt malabsorption should be considered and investigated.

Diagnosis of small intestinal bacterial overgrowth: the challenges persist!

Small intestinal bacterial overgrowth was originally defined in the context of an overt malabsorption syndrome and diagnostic tests were developed and validated accordingly. More recently, the concept of intestinal contamination with excessive numbers of bacteria, especially those of colonic type, has been extended beyond the bounds of frank maldigestion and malabsorption to explain symptomatology in disorders as diverse as irritable bowel syndrome, celiac sprue and nonalcoholic fatty liver disease. Owing to a lack of consensus with regard to the optimal diagnostic criteria (the 'gold standard') for the diagnosis of bacterial overgrowth, the status of these new concepts is unclear. This review sets out to critically appraise the various diagnostic approaches that have been taken and are currently employed to diagnose small intestinal bacterial overgrowth.

Gastrointestinal microbiota in irritable bowel syndrome: their role in its pathogenesis and treatment

Irritable bowel syndrome (IBS) is a chronic disorder characterized by abdominal pain, change in bowel habit, and bloating. It has traditionally been viewed as a disorder of visceral hypersensitivity heavily influenced by stress, and therefore therapeutic strategies to date have largely reflected this. However, more recently, there is good evidence for a role of the gastrointestinal (GI) microbiota in its pathogenesis. Changes in fecal microbiota, the use of probiotics, the phenomenon of postinfectious IBS, and the recognition of an upregulated host immune system response suggest that an interaction between the host and GI microbiota may be important in the pathogenesis of IBS. This article explores the role of the GI microbiota in IBS and how their modification might lead to therapeutic benefit.

Rifaximin treatment for symptoms of irritable bowel syndrome

OBJECTIVE

To evaluate the role of rifaximin in the treatment of symptoms associated with irritable bowel syndrome (IBS).

DATA SOURCES

Clinical literature was accessed through MEDLINE (1990-September 2007) using the terms rifaximin, small intestinal bacterial overgrowth (SIBO), bacterial overgrowth, and irritable bowel syndrome. Additionally, references in publications identified in the search were reviewed for relevant information.

STUDY SELECTION AND DATA EXTRACTION

All articles published in English identified from the data source were evaluated. Randomized clinical trials in adult populations were included.

DATA SYNTHESIS

IBS is a common functional bowel disorder of unknown etiology. Some evidence suggests that symptoms are secondary to bacterial overgrowth in the small intestine. Rifaximin, a nonsystemic antibiotic that targets the gastrointestinal tract, has been evaluated in the treatment of SIBO. Six studies that evaluated rifaximin in either IBS, with or without documented SIBO, or SIBO alone, were reviewed. Significant symptom improvement was reported, and in some cases, correlated with reductions in hydrogen breath tests, suggesting successful treatment of bacterial overgrowth. Data are limited by controversial diagnostic techniques for SIBO, small sample sizes, the unpredictable course of the disorder, and variability in clinical trial methodology that prevents direct comparison.

CONCLUSIONS

Rifaximin offers a potential new therapeutic option for patients with refractory IBS. Larger, well-designed trials are necessary to elucidate the role of rifaximin in the treatment of this disorder.

Clinical application progress of Rifaximin in the treatment of digestive diseases

Rifaximin, a derivative of rifamycin, has high antibacterial activity on various kinds of Gram-positive and -negative aerobes and anaerobes, and it is a new drug in the treatment of giardiasis. Rifaximin is not easy to be absorbed after oral administration, and mild systemic adverse reaction is the main characteristic. Recently, Rifaximin has been widely and effectively used in the therapy of many diseases related to intestinal bacterial infection such as hepatic encephalopathy, diverticular disease, overgrowth of intestinal bacteria, inflammatory bowel disease (IBD) and H. pylori infection. The above advances were reviewed in the present article.