Bacteria and irritable bowel syndrome: the evidence for small intestinal bacterial overgrowth

Meta-analysis of the efficacy of probiotics to treat diarrhea

BACKGROUND

To collect the published trials of probiotics in the treatment of diarrhea and to strictly evaluate and systematically analyze the efficacy of probiotics use for the prevention and treatment of patients with diarrhea.

METHODS

We searched domestic and foreign literature published between January 2016 and July 2022 to find randomized control trials that used probiotics to treat diarrhea. Only studies published in English were considered. The quality of the included literatures was assessed by using the methods provided in the Cochrane Handbook. Valid data were extracted and analyzed by meta- analysis using the Software RevMan5.2.

RESULTS

Total 16 trials and 1585 patients were included. The results of the meta- analysis showed that in comparison with the simple Western medicine treatment group or placebo, the added use of probiotics could improve stool frequency, stool morphology, and related irritable bowel syndrome symptoms.

CONCLUSION

The added use of probiotics can further improve clinical outcomes in the patients with diarrhea; however, the implementation of larger and higher quality clinical trials is necessary to verify this conclusion.

Future Trends in Semiconducting Gas-Selective Sensing Probes for Skin Diagnostics

This paper presents sensor nanotechnologies that can be used for the skin-based gas “smelling” of disease. Skin testing may provide rapid and reliable results, using specific “fingerprints” or unique patterns for a variety of diseases and conditions. These can include metabolic diseases, such as diabetes and cholesterol-induced heart disease; neurological diseases, such as Alzheimer’s and Parkinson’s; quality of life conditions, such as obesity and sleep apnea; pulmonary diseases, such as cystic fibrosis, asthma, and chronic obstructive pulmonary disease; gastrointestinal tract diseases, such as irritable bowel syndrome and colitis; cancers, such as breast, lung, pancreatic, and colon cancers; infectious diseases, such as the flu and COVID-19; as well as diseases commonly found in ICU patients, such as urinary tract infections, pneumonia, and infections of the blood stream. Focusing on the most common gaseous biomarkers in breath and skin, which is nitric oxide and carbon monoxide, and certain abundant volatile organic compounds (acetone, isoprene, ammonia, alcohols, sulfides), it is argued here that effective discrimination between the diseases mentioned above is possible, by capturing the relative sensor output signals from the detection of each of these biomarkers and identifying the distinct breath print for each disease.

The Effectiveness of Synbiotic Preparation Containing Lactobacillus and Bifidobacterium Probiotic Strains and Short Chain Fructooligosaccharides in Patients with Diarrhea Predominant Irritable Bowel Syndrome-A Randomized Double-Blind, Placebo-Controlled Study

The purpose of the randomized double-blind placebo-controlled trial was to assess the effectiveness of synbiotic preparation containing probiotic Lactobacillus rhamnosus FloraActive™ 19070-2, Lactobacillus acidophilus DSMZ 32418, Bifidobacterium lactis DSMZ 32269, Bifidobacterium longum DSMZ 32946, Bifidobacterium bifidum DSMZ 32403 and fructooligosaccharides in adult patients with diarrhea-dominant IBS (IBS-D). The study included eighty patients with moderate and severe IBS-D who were randomized to receive synbiotics or placebo for eight weeks. Finally, a total of sixty-eight patients finished the study. The primary endpoints included the assessment of the symptoms’ severity with IBS symptom severity scale (IBS-SSS), an improvement of IBS global symptoms with Global Improvement Scale (IBS-GIS) and adequate relief of symptoms after four and eight weeks of therapy. Secondary endpoints, which were collected by telephone interviewers three times a week included the assessment of individual IBS symptoms and adverse events. Synbiotic treatment in comparison to placebo significantly improved IBS-GIS (p = 0.043), and IBS-SSS score inducing a decrease in the total IBS-SSS (p = 0.042) and in domain-specific scores related to flatulence (p = 0.028) and bowel habit (p = 0.028) after four and eight weeks. Patients treated with synbiotics reported in weekly observations a significant amelioration in a feeling of incomplete bowel movements, flatulence, pain, stool pressure and diarrheal stools compared to those receiving placebo. There were no differences in adverse events between both groups. Concluding, the multi-strain synbiotic preparation was associated with a significant improvement in symptoms in IBS-D patients and was well-tolerated. These results suggest that the use of synbiotics offers a benefit for IBS-D patients. [Clinicaltrials.gov NCT04206410 registered 20 December 2019].

A randomized placebo-controlled clinical trial of a multi-strain probiotic formulation (Bio-Kult®) in the management of diarrhea-predominant irritable bowel syndrome

Background

Accumulating evidence supports the view that an imbalance of gut bacteria contributes to IBS, and that increasing the mass of beneficial species may reduce the numbers of pathogenic bacteria and help alleviate symptoms.

Methods

In this double-blind trial 400 adult patients with moderate-to-severe symptomatic diarrhea-predominant IBS (IBS-D) were randomized to treatment with the multi-strain probiotic Bio-Kult® (14 different bacterial strains) or placebo for 16 weeks. The change in severity and frequency of abdominal pain was the primary outcome measure.

Results

Probiotic treatment significantly improved the severity of abdominal pain in patients with IBS-D. A 69% reduction for probiotic versus 47% for placebo (p < 0.001) equates to a 145 point reduction on the IBS-severity scoring system (IBS-SSS). The proportion of patients who rated their symptoms as moderate-to-severe was reduced from 100% at baseline to 14% for the multi-strain probiotic at follow-up (month 5) versus 48% for placebo (p < 0.001). Also, the number of bowel motions per day from month 2 onwards was significantly reduced in the probiotic group compared with the placebo group (p < 0.05). In addition to relieving symptoms, the probiotic markedly improved all dimensions of quality of life in the 34-item IBS-Quality of Life (IBS-QoL) questionnaire. No serious adverse events were reported.

Conclusions

The multi-strain probiotic was associated with significant improvement in symptoms in patients with IBS-D and was well-tolerated. These results suggest that probiotics confer a benefit in IBS-D patients which deserves further investigation.

Trial registration

[Clinicaltrials.gov NCT03251625; retrospectively registered on August 9, 2017].

Electronic supplementary material

The online version of this article (doi:10.1186/s12876-018-0788-9) contains supplementary material, which is available to authorized users.

The Role of Diet in the Treatment of Irritable Bowel Syndrome: A Systematic Review

Irritable bowel syndrome (IBS) is a multifaceted illness involving maladaptive shifts in the gut microbiota that affect the enteric nervous and immune systems, mucosal barrier function, the balance of neurotransmitters and hormones, and emotional well-being. There is abundant evidence indicating that certain foods elicit symptoms in IBS. Numerous elimination-type diets have been shown to alleviate symptoms. However, among these, the most controversial is a group of foods called fructo, oligo-, di-, and monosaccharides and polyols (FODMAPs). This paper reviews the role of diet and systematically analyze the literature for the role of FODMAPs in IBS.

Serial Frozen Fecal Microbiota Transplantation in the Treatment of Chronic Intestinal Pseudo-obstruction: A Preliminary Study

Background/Aims

Chronic intestinal pseudo-obstruction (CIPO) is a serious, life-threatening motility disorder that is often related to bacterial overgrowth. Fecal microbiota transplantation (FMT) results in restoration of the normal intestinal microbial community structure. We investigated the efficacy of FMT in the treatment of CIPO patients.

Methods

Nine patients (age 18–53 years) with CIPO were enrolled in this prospective, open-label study. Patients received FMT for 6 consecutive days through nasojejunal (NJ) tubes and were followed up for 8 weeks after treatment. We evaluated the rate of clinical improvement and remission, feeding tolerance of enteral nutrition, and CT imaging scores of intestinal obstructions. Lactulose hydrogen breath tests were performed before FMT and 8 weeks after FMT to evaluate for the presence small intestinal bacterial overgrowth (SIBO).

Results

FMT significantly alleviated bloating symptoms, and symptoms of pain were relieved 2 weeks after FMT. Enteral nutrition administered through a NJ tube after FMT was well-tolerated by 66.7% (6/9) of patients. CT scores of intestinal obstructions were significantly reduced after FMT (P = 0.014). SIBO was eliminated in 71.0% (5/7) of patients.

Conclusions

This pilot study demonstrated the safety of using FMT. FMT may relieve symptoms in selected patients with CIPO. FMT may also improve patient tolerance of enteral nutrition delivered via a NJ tube.

Lactulose Breath Test Gas Production in Childhood IBS Is Associated With Intestinal Transit and Bowel Movement Frequency

OBJECTIVES

In adults with irritable bowel syndrome (IBS), bacterial gas production (colonic fermentation) is related to both symptom generation and intestinal transit. Whether gas production affects symptom generation, psychosocial distress, or intestinal transit in childhood IBS is unknown.

METHODS

Children (ages 7-17 years) with pediatric Rome III IBS completed validated psychosocial questionnaires and a 2-week daily diary capturing pain and stooling characteristics. Stool form determined IBS subtype. Subjects then completed a 3-hour lactulose breath test for measurement of total breath hydrogen and methane production. Carmine red was used to determine whole intestinal transit time.

RESULTS

A total of 87 children (mean age 13 ± 2.6 [standard deviation] years) were enrolled, of whom 50 (57.5%) were girls. All children produced hydrogen and 51 (58.6%) produced methane. Hydrogen and methane production did not correlate with either abdominal pain frequency/severity or psychosocial distress. Hydrogen and methane production did not differ significantly by IBS subtype. Methane production correlated positively with whole intestinal transit time (r = 0.31, P < 0.005) and inversely with bowel movement frequency (r = -0.245, P < 0.05). Methane production (threshold 3 ppm) as a marker for identifying IBS-C had a sensitivity of 60% and specificity of 42.9%.

CONCLUSIONS

Lactulose breath test total methane production may serve as a biomarker of whole intestinal transit time and bowel movement frequency in children with IBS. In children with IBS, lactulose breath test hydrogen and methane production did not, however, correlate with abdominal pain, IBS subtype, or psychosocial distress.

The comparison of treatments with and without azithromycin in irritable bowel syndrome with diarrhea-predominant in gastrointestinal Clinic of Al-Zahra Hospital, Isfahan, Iran

BACKGROUND

Irritable bowel syndrome (IBS) is a common gastrointestinal disorder. Recent studies suggest the importance of gut flora in the pathophysiology of it. Therefore, antibiotics have demonstrated a substantial benefit to reduce gut flora. Having few side effects, and applying one-dose per day, we studied the effect of azithromycin to treat IBS.

MATERIALS AND METHODS

One hundred and twenty-six patients enrolled a randomized, double-blind, placebo-controlled study. The treatment group received azithromycin in addition to common treatment. Patients were followed for 12 weeks. Patients completed daily diaries documenting their symptoms.

RESULTS

One hundred and thirteen patients completed the study. The onset of relief occurred significantly sooner, and duration of relief was significantly longer in azithromycin group. Movement, abdominal pain, bloating, and gas were significantly better in azithromycin group. Monthly results showed superior relief in bloating, gas, overall symptom, and overall bloating during 3 months. Significantly more patients in azithromycin group felt relief in bloating and gas and had greater consistency relief in almost all weeks.

CONCLUSION

In our study, azithromycin significantly relieved most symptoms, such as abdominal pain, bloating, and gas. Overall symptom and overall bloating were relieved significantly in more patients in the intervention group in all weeks.

Small intestinal bacterial overgrowth is associated with irritable bowel syndrome and is independent of proton pump inhibitor usage

BACKGROUND

Current knowledge suggests that small intestinal overgrowth participates in the pathogenesis of irritable bowel syndrome. It is questionable if this association is modulated by intake of proton pump inhibitors (PPIs).

METHODS

In a prospective study, quantitative cultures of duodenal aspirates were performed for aerobic species in 897 consecutive patients undergoing upper GI tract endoscopy. SIBO was defined as equal to or more than 10(3) cfu/ml. The effect of PPI intake on the relationship between SIBO and IBS was the primary endpoint.

RESULTS

Analysis among patients without any history of PPI intake (n = 713) showed that odds ratio (OR) for IBS in the event of SIBO was 5.63 (3.73-8.51, p < 0.0001); this was 4.16 (1.91-9.06) when analysis was done among patients with history of PPI intake (n = 184, p: 0.498 between patients without and with PPI intake). Multiple logistic regression analysis found that factors independently associated with SIBO were age above or equal to 60 years (OR: 2.36), body mass index more than or equal to 22 kg/m(2) (OR: 0.60), presence of IBS (OR: 6.29), type 2 diabetes mellitus (OR: 1.59) and gastritis (OR: 0.47).

CONCLUSIONS

The association between IBS and SIBO was completely independent from PPI intake. Although gastritis was protective against SIBO, results show that PPI intake cannot prime SIBO.

Hydrogen sulphide in exhaled breath: a potential biomarker for small intestinal bacterial overgrowth in IBS

There is a pressing need to develop a novel early-detection strategy for the precise evolution of small intestinal bacterial overgrowth (SIBO) in irritable bowel syndrome (IBS) patients. The current method based on a hydrogen breath test (HBT) for the detection of SIBO is highly controversial. HBT has many limitations and drawbacks. It often fails to indentify SIBO when IBS individuals have 'non-hydrogen-producing' colonic bacteria. Here, we show that hydrogen sulphide (H2S) in exhaled breath is distinctly altered for diarrhea-predominant IBS individuals with positive and negative SIBO by the activity of intestinal sulphate-reducing bacteria. Subsequently, by analyzing the excretion kinetics of breath H2S, we found a missing link between breath H2S and SIBO when HBT often fails to diagnose SIBO. Moreover, breath H2S can track the precise evolution of SIBO, even after the eradication of bacterial overgrowth. Our findings suggest that the changes in H2S in the bacterial environment may contribute to the pathogenesis of SIBO and the breath H2S as a potential biomarker for non-invasive, rapid and precise assessment of SIBO without the endoscopy-based microbial culture of jejunal aspirates, and thus may open new perspectives into the pathophysiology of SIBO in IBS subjects.

Is fecal microbiota transplantation (FMT) an effective treatment for patients with functional gastrointestinal disorders (FGID)?

BACKGROUND

Despite its high prevalence and significant effect on quality of life, the etiology of functional gastrointestinal disorders (FGID), and specifically irritable bowel syndrome (IBS), has yet to be fully elucidated. While alterations in immunity, motility, and the brain-gut axis have been implicated in disease pathogenesis, the intestinal microbiota are increasingly being shown to play a role and numerous studies have demonstrated significant differences from normal in the intestinal flora of patients with FGID, and between types of FGID. Fecal microbiota transplantation (FMT) is a curative therapy for Clostridium difficile infection (CDI), a disease hallmarked by intestinal dysbiosis, and FMT is now being explored as a means to also restore intestinal homeostasis in FGID.

PURPOSE

This review aims to investigate the role of intestinal microbiota in the pathogenesis of FGID, the implications of FMT for the treatment of FGID, and the challenges encountered in measuring response to a specific intervention in patients with FGID.

Associations between IL-1RA polymorphisms and small intestinal bacterial overgrowth among patients with irritable bowel syndrome from India

BACKGROUND

Low-grade inflammation (controlled by pro and anti-inflammatory molecules), induced by gut microbes in patients with small intestinal bacterial overgrowth (SIBO), may be associated with irritable bowel syndrome (IBS). Polymorphisms of IL-RA gene (anti-inflammatory) was evaluated in IBS and healthy subjects (HS); small intestinal mucosal IL-1α and β levels (pro-inflammatory) in relation to the presence of SIBO were evaluated in a subset of patients.

METHODS

Two hundred and twenty-one IBS patients and 273 age- and gender-matched HS were included. Exactly 209 of 221 patients (Rome III) and 273 HS were genotyped (PCR) for IL-1RA polymorphism. Mucosal IL-1α and β levels (pg/mg of biopsy) were estimated (ELISA) in 82/221 patients with and without SIBO (≥10(5)  CFU/mL upper gut aspirate bacteria).

KEY RESULTS

Genotype 1/1 (IL-1RA over-producer) was less frequent among patients than controls (p = 0.007); genotypes 1/3 (p = 0.012, OR = 3.301, 95% CI = 1.31-8.35) and 2/3 (both under-producers; p = 0.009, OR = 7.703, 95% CI = 1.66-35.82) were commoner among IBS. Fifteen of 82 (18.3%) patients had SIBO. Levels of IL-1α and β were higher among patients with SIBO than without (IL-1α: 35.4 [20.1-66.8] vs 25.5 [4.2-65.3], p < 0.001; IL-1β: 206.8 [133.5-365.9] vs 93.1 [25.5-197.7], p < 0.001) and those with bloating than without (p = 0.012; p = 0.015). IL-1β was higher among patients with Bristol stool type 6 than those with type 1-2 (p = 0.002) and type 3-5 (p = 0.007).

CONCLUSIONS & INFERENCES

Polymorphisms 1/1 (IL-1RA over-producer) was infrequent and 1/3 and 2/3 (under-producers) frequent among IBS. Increased IL-1α and β levels were associated with SIBO. Increased IL-1β level was predominantly associated with bloating and loose stools (Bristol type 6).

Irritable bowel syndrome: contemporary nutrition management strategies

Irritable bowel syndrome is a complex disorder whose pathophysiology involves alterations in the enteric microbiota, visceral hypersensitivity, gut immune/barrier function, hypothalamic-pituitary-adrenal axis regulation, neurotransmitters, stress response, psychological factors, and more. The importance of diet in the management of irritable bowel syndrome has taken center stage in recent times as the literature validates the relationship of certain foods with the provocation of symptoms. Likewise, a number of elimination dietary programs have been successful in alleviating irritable bowel syndrome symptoms. Knowledge of the dietary management strategies for irritable bowel syndrome will help guide nutritionists and healthcare practitioners to deliver optimal outcomes. This tutorial reviews the nutrition management strategies for irritable bowel syndrome.

Gastrointestinal motility disorder assessment in systemic sclerosis

OBJECTIVES

SSc is a clinically heterogeneous and generalized disease, characterized by thickness of the connective tissue of the skin and internal organs, such as the digestive tract, impairing gastrointestinal (GI) motility. Our aim is to evaluate retrospectively abnormalities of oesophageal motility, gastric emptying, oro-cecal transit time (OCTT) and small intestine bacterial overgrowth (SIBO) in a large cohort of SSc patients.

METHODS

Ninety-nine SSc patients were included in the study. Forty-two patients underwent oesophageal conventional manometry, 45 performed a [(13)C]octanoic acid breath test to measure gastric emptying time and all 99 patients performed a lactulose breath test in order to evaluate OCTT and SIBO. Data were compared with healthy controls.

RESULTS

In SSc patients, median lower oesophageal sphincter (LOS) pressure [14 mmHg (25th-75th; 8-19) vs 24 mmHg (19-28); P < 0.01] and median wave amplitude [30 mmHg (16-70) vs 72 mmHg (48-96); P < 0.01] were lower than in controls. Oesophageal involvement, defined as reduced LOS pressure and ineffective oesophageal motility pattern, was encountered in 70% of SSc patients. A delayed gastric emptying time was present in 38% of SSc patients: mean t½ was 141 ± 79 min vs 90 ± 40 min of controls (P < 0.01). Also, OCTT was significantly delayed in SSc: median OCTT was 160 min (25th-75th; 135-180) vs 105 min (25th-75th; 90-135) of controls (P < 0.01). SIBO was observed in 46% of SSc compared with 5% of controls (P < 0.01).

CONCLUSION

GI involvement is very frequent in SSc patients. Oesophagus and small bowel are more frequently impaired, whereas delayed gastric emptying is less common.

Galleria mellonella as a model host to study gut microbe homeostasis and brain infection by the human pathogen listeria monocytogenes

The gastrointestinal tract in both mammals and insects is associated with microbes (collectively the microbiota), which are controlled by the intestinal immune system. These microbes regulate pathogens that can infect gut epithelial cells, and there is increasing evidence for a reciprocal relationship between beneficial and pathogenic bacteria in the gut and the intestinal immune system. Deciphering these complex interactions between the microbiota and intestinal immune system in mammals requires surrogate model systems, such as larvae of the greater wax moth Galleria mellonella. The exposure of G. mellonella microbiota to antibiotics induces immunity and stress-related genes in the intestine. The model can also provide insight into the virulence mechanisms of pathogens such as Listeria monocytogenes in the human gut and brain. We also discuss the current uses of G. mellonella as a model to develop therapeutic strategies against listeriosis.

Chronic gastrointestinal consequences of acute infectious diarrhea: evolving concepts in epidemiology and pathogenesis

Acute infectious diarrhea is a frequent occurrence both in the developing world, where it results in considerable mortality, and in developed countries, where it accounts for a significant number of health visits, hospitalizations, and medical and non-medical losses. Recent evidence in basic, clinical, and epidemiological science domains has emerged that suggest that the burden caused by these infections is not limited to the acute illness, but may result in triggering or contributing to the pathogenesis of a number of chronic health problems. This review considers the breadth of this information for the purpose of consolidating what is currently known, identifying gaps in knowledge, and describing future directions and policy implications related to the chronic consequences of acute infectious diarrhea. A unifying hypothesis of this review is that infections may trigger a number of long-lasting changes in gut physiology and immunity that can increase the risk to a variety of chronic gastrointestinal diseases, particularly in genetically susceptible individuals.

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.

New insights into the impact of the intestinal microbiota on health and disease: a symposium report

The present report summarises key insights from a recent symposium focusing on the impact of the intestinal microbiota on health and disease. A more appropriate definition of health was proposed since health maintenance is a dynamic process better assessed in terms of ability to adapt to stress and maintain physiological homeostasis. Biomarkers specifically for health are needed; use of challenge models and subjects with suboptimal health or specific disease risk were advised. The complexity of interactions between external factors, the intestinal epithelium, intestinal microbiota, the immune system and health was exemplified by describing the effects of antibiotics, the Western diet and non-digestible carbohydrates on the microbiota. The association of certain bacteria with different states of health or disease was acknowledged but also that is not always clear whether this is a cause or effect. Recent identification of three robust faecal metagenome clusters may advance this understanding. It was speculated that knowledge of the intestinal microbiota profile may eventually help in the diagnosis of health risks and choice of therapy. It was agreed that beneficial manipulation of the commensal microbiota can improve health outcome. For this purpose, three areas were reviewed. Firstly, research into probiotics as vaccine adjuvants was considered useful for substantiation of immune function claims. Secondly, positive results with certain probiotics and synbiotics for colorectal cancer are emerging, mostly fromin vitroand animal studies. Finally, studies in endurance athletes have shown strain-specific probiotic benefit in terms of maintenance of immune function and, for certain strains, reduction of episodes of respiratory and/or gastrointestinal tract infections.

Irritable bowel syndrome, gut microbiota and probiotics

Irritable bowel syndrome (IBS) is a complex disorder characterized by abdominal symptoms including chronic abdominal pain or discomfort and altered bowel habits. The etiology of IBS is multifactorial, as abnormal gut motility, visceral hypersensitivity, disturbed neural function of the brain-gut axis and an abnormal autonomic nervous system are all implicated in disease progression. Based on recent experimental and clinical studies, it has been suggested that additional etiological factors including low-grade inflammation, altered gut microbiota and alteration in the gut immune system play important roles in the pathogenesis of IBS. Therefore, therapeutic restoration of altered intestinal microbiota may be an ideal treatment for IBS. Probiotics are live organisms that are believed to cause no harm and result in health benefits for the host. Clinical efficacy of probiotics has been shown in the treatment or prevention of some gastrointestinal inflammation-associated disorders including traveler's diarrhea, antibiotics-associated diarrhea, pouchitis of the restorative ileal pouch and necrotizing enterocolitis. The molecular mechanisms, as cause of IBS pathogenesis, affected by altered gut microbiota and gut inflammation-immunity are reviewed. The effect of probiotics on the gut inflammation-immune systems and the results from clinical trials of probiotics for the treatment of IBS are also summarized.

The role of methane in intestinal diseases

The volume of human intestinal gas is about 200 ml, and it is derived from complex physiological processes including swallowed air, diffusion from bloodstream into the lumen, and particularly intraluminal production by chemical reactions and bacterial fermentation. Gas is continuously removed by eructation, anal evacuation, absorption through the intestinal mucosa, and bacterial consumption. More than 99% of it is composed of hydrogen, oxygen, carbon dioxide, nitrogen, and other odoriferous gases. Methane (CH4) production is detectable in about one third of healthy adult individuals. In the past years, several studies have been focused on CH4 metabolism at the intestinal level and on the putative association between this gas and the pathophysiology of organic and functional bowel disorders. An overview of the present knowledge about the physiology of CH4 metabolism and its role in intestinal diseases is provided in this report.

New horizons for the infectious diseases specialist: how gut microflora promote health and disease

The human intestine provides an expansive interface for interactions with the microflora. Increasing data support the hypothesis that host-microflora relationships are markedly dynamic, contributing to host health and disease pathogenesis. Despite outnumbering human cells 10-fold, the microflora most often assist the host through symbiotic relationships. The microflora are involved in maximizing host utilization of nutrients, induction of host immune responses, and promotion of intestinal cell and mucosal development. However, evolving data suggest that disturbances in this symbiotic relationship can lead the microflora to be pathogenic in diverse conditions such as inflammatory bowel disease, irritable bowel disease, obesity, graft-versus-host disease, HIV immunopathogenesis, and possibly cancer. Defining those microflora attributes that result in health and those that trigger disease is key to harnessing the microflora to promote human health.

Current insights in to the pathophysiology of Irritable Bowel Syndrome

Irritable Bowel Syndrome (IBS) represents a functional disorder of gastrointestinal tract without the presence of an anatomic defect, in which abdominal pain is relieved with defecation and is associated with altered bowel habits.

IBS includes a wide range of symptoms while its pathophysiology is very complicated. Recent studies indicate that the most important mechanisms include visceral sensitivity, abnormal gut motility and autonomous nervous system dysfunction. The interactions between these three mechanisms make bowel's function susceptible to many exogenous and endogenous factors like gastrointestinal flora, feeding and psychosocial factors. Recent data indicate that according to the above mechanisms, the influence of genetic factors and polymorphisms of human DNA in the development of IBS is equally important.

Altered intestinal microbiota in irritable bowel syndrome

Recent studies have suggested that alterations in the composition of the intestinal microbiota may play an important role in irritable bowel syndrome (IBS) symptoms. However, an association between the composition of the intestinal microbiota and IBS symptoms has not been clearly demonstrated. In the current issue of the Journal, Tana et al. suggest that altered intestinal microbiota contributes to the symptoms of IBS through increased levels of organic acids. In fecal samples, IBS patients had significantly higher numbers of Veillonella and Lactobacillus than healthy controls. They also showed significantly higher levels of acetic acid and propionic acid. Furthermore, IBS patients with high acetic acid or propionic acid levels presented more severe symptoms, impaired quality of life and negative emotions. These results are in accordance with the concept that the gut microbiota influences the sensory, motor and immune system of the gut and interacts with higher brain centers. Small intestinal bacterial overgrowth observed in a subset of IBS patients describes quantitative changes in the small intestinal microbiota. Data on qualitative changes in the gut microbiota in IBS patients are lacking. Different members of gut bacteria may have different influence on gut function. The concepts identified here may lead to the development of novel therapeutic strategies for IBS using manipulation of the intestinal microbiota.

Innate immunity and gut-microbe mutualism in Drosophila

Metazoan guts face a wide variety of microorganisms upon exposure to the environment, including beneficial symbionts, non-symbionts, food-borne microbes and life-threatening pathogens. Recent evidence has shown that the innate immunity of gut epithelia, such as anti-microbial peptide- and reactive oxygen species-based immune systems, actively participate in gut-microbe homeostasis by shaping the commensal community while efficiently eliminating unwanted bacteria. Therefore, elucidation of the regulatory mechanism by which gut innate immunity occurs at the molecular level will provide a novel perspective of gut-microbe mutualisms as well as of gut diseases caused by alterations in the innate immunity.

Small intestinal bacterial overgrowth in irritable bowel syndrome: are there any predictors?

BACKGROUND

Small intestinal bacterial overgrowth (SIBO) is a condition in which excessive levels of bacteria, mainly the colonic-type species are present in the small intestine. Recent data suggest that SIBO may contribute to the pathophysiology of Irritable bowel syndrome (IBS). The purpose of this study was to identify potential predictors of SIBO in patients with IBS.

METHODS

Adults with IBS based on Rome II criteria who had predominance of bloating and flatulence underwent a glucose breath test (GBT) to determine the presence of SIBO. Breath samples were obtained at baseline and at 30, 45, 60, 75 and 90 minutes after ingestion of 50 g of glucose dissolved in 150 mL of water. Results of the glucose breath test, which measures hydrogen and methane levels in the breath, were considered positive for SIBO if 1) the hydrogen or methane peak was >20 ppm when the baseline was <10 ppm, or 2) the hydrogen or methane peak increased by 12 ppm when baseline was >or=10 ppm.

RESULTS

Ninety-eight patients were identified who underwent a GBT (mean age, 49 y; 78% female). Thirty-five patients (36%) had a positive GBT result suggestive of SIBO. A positive GBT result was more likely in patients >55 years of age (odds ratio [OR], 3.6; 95% confidence interval [CI], 1.4-9.0) and in females (OR, 4.0; 95% CI, 1.1-14.5). Hydrogen was detected more frequently in patients with diarrhea-predominant IBS (OR, 8; 95% CI, 1.4-45), and methane was the main gas detected in patients with constipation-predominant IBS (OR, 8; 95% CI, 1.3-44). There was no significant correlation between the presence of SIBO and the predominant bowel pattern or concurrent use of tegaserod, proton pump inhibitors, or opiate analgesics.

CONCLUSIONS

Small intestinal bacterial overgrowth was present in a sizeable percentage of patients with IBS with predominance of bloating and flatulence. Older age and female sex were predictors of SIBO in patients with IBS. Identification of possible predictors of SIBO in patients with IBS could aid in the development of successful treatment plans.

Possible role for TRPV1 in neomycin-induced inhibition of visceral hypersensitivity in rat

Transient receptor ion channel 1 (TRPV1) is a nociceptor involved in visceral hypersensitivity. Aminoglycosides like neomycin are not only potent antibiotics but in vitro data suggest that neomycin also acts as a TRPV1-antagonist and alleviates somatic pain responses. To what extent neomycin reduces visceral hypersensitivity remains unknown. Therefore, we aimed to investigate whether neomycin can inhibit in vivo TRPV1-dependent hypersensitivity responses in two rat models of visceral pain. In the first model rats were pretreated with intraperitoneal (i.p.) capsazepine, the selective TRPV1 antagonist SB-705498, neomycin or vehicle alone and 30 min later instilled with intracolonic TRPV1-activating capsaicin. Likewise, rats were pretreated with 10 days oral neomycin and then subjected to intracolonic capsaicin. The visceromotor response (VMR) to distension was measured before and after capsaicin application. In addition, the VMR to distension was measured in adult maternal separated rats before and after acute stress. Before the 2nd distension protocol these rats were treated with i.p. neomycin, amoxycillin or vehicle alone. Our results showed that capsaicin administration induced an enhanced VMR to distension that was prevented by i.p. capsazepine, SB-705498 and neomycin. Oral neomycin treatment changed bacterial faecal content but could not inhibit capsaicin induced visceral hypersensitivity. In maternal separated rats acute stress induced an enhanced response to distension that was reversed by i.p. neomycin, but not amoxycillin. These data indicate that (i.p.) neomycin can inhibit visceral hypersensitivity to distension in a nonbactericidal manner and suggest that TRPV1-modulation may be involved.

Incidence of predominant methanogenic flora in irritable bowel syndrome patients and apparently healthy controls from North India

BACKGROUND

Flatulence is a common symptom in patients with irritable bowel syndrome (IBS). This may be due to production of hydrogen by intestinal flora. With the presence of methanogenic flora, 4 mol of hydrogen (H(2)) are used with 1 mol of carbon dioxide (CO(2)) to produce 1 mol of methane (CH(4)), a process greatly reducing the volume of gas in the colon. However, the prevalence of methanogenic flora has not yet been reported in healthy and IBS patients from North India. Therefore, this study was planned.

METHODS

This study was conducted prospectively and included 345 patients with irritable bowel syndrome (fulfilling Rome II criteria) and 254 age- and gender-matched apparently healthy controls. Each subject underwent a hydrogen breath test using 10 g lactulose after an overnight fast. An SC Microlyser from Quintron, USA, was used to measure methane and hydrogen at baseline and at every 30 min for 4 h. Subjects with fasting methane concentration <10 p.p.m. were labeled as low methane producers (LMPs) and > 10 p.p.m. as predominant methane producers (PMPs).

RESULTS

The IBS and control groups included 66.78% and 67.53% men, respectively. Mean age in the two groups was 48.52 +/- 30.54 years (range 15-68 years) and 45.67 +/- 30.54 years (range 15-78 years), respectively. Prevalence of predominant methanogenic flora in IBS and control groups was 14.5% (50/345) and 34.6% (88/254), respectively (P < 0.001). Fifty-two out of 254 (20.6 %) were PMPs and 36 out of 254 (14.0%) were LMPs in controls. In contrast to this, IBS patients had 17 out of 354 (4.9%) that were PMPs and 33 out of 345 (9.6%) that were LMPs.

CONCLUSION

Methanogenic flora was significantly lower in IBS patients from North India than in apparently healthy subjects. This may be one of the causes of flatulence in IBS patients.

Alterations in the intestinal microbiota and functional bowel symptoms

Functional gastrointestinal disorders (FGIDs) are highly prevalent in Western countries yet no single mechanism or etiological agent that initiates IBS has been identified. Current research has implicated the intestinal microbiota with FGIDs. This article reviews the available literature/data regarding the intestinal microbiota and FGIDS. The possible relationships between the intestinal microbiota and the intestinal function and functional bowel symptoms are discussed.

Small intestinal bacterial overgrowth in patients suffering from scleroderma: clinical effectiveness of its eradication

OBJECTIVES

After the skin, the gastrointestinal tract is the second most common target of systemic sclerosis (SSc).

AIM

Our aims were to investigate orocecal transit time (OCTT) and the presence of small intestinal bacterial overgrowth (SIBO) in SSc as a cause of intestinal symptoms.

METHODS

Fifty-five SSc patients and 60 healthy controls, sex and age matched, entered the study. Enrolled subjects completed a questionnaire for intestinal symptoms and a global symptomatic score (GSS) was calculated. OCTT and the presence of SIBO were assessed by a lactulose breath test (LBT). Patients with SIBO were treated with rifaximin 1,200 mg/day for 10 days. Finally, a second questionnaire and LBT were performed 1 month after the end of therapy.

RESULTS

The prevalence of SIBO was higher in SSc patients compared with controls (30/54 vs 4/60, respectively, P < 0.001). OCTT was significantly slower in SSc patients compared with controls (150 min, 25-75th percentile 142.5-165 vs 105 min, 25-75th percentile 90-135, respectively, P < 0.001). In patients with SIBO, the median GSS score was 8 (25-75th percentile 3.25-10.75). Eradication of SIBO was achieved in 73.3% of patients, with a significant reduction of symptoms in 72.7% of them (GSS score 2, 25-75th percentile 1-3, P < 0.05).

CONCLUSIONS

These data suggest that SIBO occurs more frequently in SSc patients than in controls. Intestinal symptoms in these patients may be related to this syndrome and its eradication seems useful to improve clinical features. OCTT is significantly delayed in SSc patients, suggesting an impairment of intestinal motility, a further risk factor for the development of SIBO.

Alterations in intestinal microbial flora and human disease

PURPOSE OF REVIEW

To highlight the evidence supporting the role of altered commensal gut flora in human disease. While the contribution of the indigenous gut microbial community is widely recognized, only recently has there been evidence pointing to indigenous flora in disease.

RECENT FINDINGS

This review discusses recent evidence pointing to the role of altered commensal gut flora in such common conditions as irritable bowel syndrome and inflammatory bowel disease. Recent studies document the intricate relationship between the vast population of microbes that live in our gut and the human host. Since increased intestinal permeability and immune activation are consequences of an altered host-gut microbial relationship, what are the clinical effects of this shift in relationship?

SUMMARY

We focus on the example of an abnormal expansion of gut microbial flora into the small bowel or small intestinal bacterial overgrowth and discuss the effects of bacterial overgrowth on the human host in acute pancreatitis, bacterial gastroenteritis, irritable bowel syndrome, inflammatory bowel disease, hepatic encephalopathy, and fibromyalgia and burn injury. The identification of the underlying role of altered commensal gut microbiota in these and other human diseases could lead to novel diagnostic and therapeutic strategies that would improve clinical outcome.

Evidence of prolonged orocecal transit time and small intestinal bacterial overgrowth in acromegalic patients

CONTEXT

Gastrointestinal abnormalities in acromegaly include dolichomegacolon, slow colonic transit, and increased prevalence of colonic polyps. Conversely, no data are available on the small intestine.

OBJECTIVE

The aim of the study was to investigate the orocecal transit time (OCTT) and the presence of small intestinal bacterial overgrowth (SIBO).

PATIENTS

A total of 41 acromegalic patients and 30 sex- and age-matched control subjects entered the study. Acromegalic patients were classified according to the medical treatment with somatostatin analogs as "treated" (n = 22) and "untreated" (n = 19), whereas according to the disease control, as "controlled" (n = 17), "uncontrolled" (n = 10), and "partially controlled" (n = 14). Patients and controls completed a questionnaire and underwent a standardized 10-g lactulose hydrogen breath test to determine the OCTT and presence of SIBO. SIBO-positive patients underwent eradication with rifaximine.

RESULTS

An increased prevalence of SIBO (18 of 41 vs. 1 of 30; P < 0.0001) and a significantly delayed OCTT (169.53 +/- 8.15 vs. 107.25 +/- 6.56 min; P < 0.0001) were evidenced in patients compared with controls. No significant statistical differences were found between "treated" or "untreated" patients positive for SIBO or between "controlled," "partially controlled," and "uncontrolled" patients. OCTT was significantly delayed in "treated" vs. "untreated" patients (183.21 +/- 9.01 and 158.89 +/- 6.38, respectively; P = 0.02) and in patients compared with controls (105.75 +/- 6.34; P < 0.0001). Rifaximine eradicated SIBO in more than 50% of patients who underwent treatment.

CONCLUSIONS

These data demonstrate for the first time that SIBO occurs more frequently in acromegalic patients, however, it can be successfully treated by a specific antibiotic. Medical therapy with somatostatin analogs does not affect SIBO prevalence. OCTT resulted significantly prolonged in both "treated" and "untreated" patients, suggesting that acromegaly determines per se an impairment of the intestinal motility. Indeed, disease control seems irrelevant on the delayed OCTT, suggesting that this alteration might be an irreversible complication of acromegaly, probably related to an autonomic intestinal disorder, as we have previously demonstrated at the cardiac level.