A systematic review of diagnostic tests for small intestinal bacterial overgrowth

Proton pump inhibitor use and the risk of small intestinal bacterial overgrowth: a meta-analysis

BACKGROUND & AIMS

Use of proton pump inhibitors (PPIs) could predispose individuals to small intestinal bacterial overgrowth (SIBO) by altering the intraluminal environment and bacterial flora. There is controversy regarding the risk of SIBO among PPI users because of conflicting results from prior studies. A systematic review and meta-analysis were performed to evaluate the association between PPI use and SIBO, using objective clinical outcome measures.

METHODS

Clinical studies comparing SIBO risk among adult users of PPIs vs nonusers were identified in MEDLINE/PubMed, EMBASE, the Cochrane Central Register of Controlled Trials, and the National Institutes of Health Clinical Trials databases through July 2012. Two reviewers independently extracted data on study characteristics and outcomes. The primary metameter was the odds ratio (OR) of SIBO among PPI users vs nonusers. Subgroup analyses were performed to examine the influence of study characteristics, such as SIBO diagnostic modality, on study outcome.

RESULTS

Eleven studies (n = 3134) met inclusion criteria. The pooled OR of SIBO in PPI users vs nonusers was 2.282 (95% confidence interval [CI], 1.238-4.205). No significant single large study or temporal effect was seen. Subgroup analysis revealed an association between SIBO and PPI use in studies that used duodenal or jejunal aspirate cultures to diagnose SIBO (OR, 7.587; 95% CI, 1.805-31.894), but no relationship was found between SIBO and PPI use in studies that used the glucose hydrogen breath test (OR, 1.93; 95% CI, 0.69-5.42). Funnel plot analysis identified 4 outlying studies, indicating the possible presence of publication bias.

CONCLUSIONS

PPI use statistically was associated with SIBO risk, but only when the diagnosis was made by a highly accurate test (duodenal or jejunal aspirate culture). Differences in study results could arise from the use of different tests to diagnose SIBO.

Antibiotics for irritable bowel syndrome: rationale and current evidence

Irritable bowel syndrome (IBS) is the most common gastrointestinal condition effecting adults in developed countries worldwide. Over the last decade, evidence has emerged suggesting that gut bacteria play a role in the pathophysiology of IBS. While difficult to identify using noninvasive means, one of the most common attributable bacterial concepts in IBS is the small intestinal bacterial overgrowth hypothesis (SIBO). In this article, we review the different mechanisms by which gut flora and, specifically, SIBO may contribute to IBS and the evidence supporting the use of various antibiotic therapies in treating IBS.

Pathological bacterial translocation in cirrhosis: pathophysiology, diagnosis and clinical implications

Bacterial translocation (BT) is defined by the passage of viable indigenous bacteria from the intestinal lumen to mesenteric lymph nodes (MLNs) and other territories, and its diagnostic criteria rely on the isolation of viable bacteria in MLNs. Small intestinal overgrowth, increased intestinal permeability and immunological alterations are the main factors involved in its pathogenesis. BT is obviously difficult to identify in patients with cirrhosis, and alternative methods have been proposed instead. Bacterial DNA detection and species identification in serum or ascitic fluid has been proposed as a reliable marker of BT. Bacterial products, such as endotoxin, or bacterial DNA can translocate to extra-intestinal sites and promote an immunological response similar to that produced by viable bacteria. Therefore, pathological BT plays an important role in the pathogenesis of the complications of cirrhosis, not only in infections, but by exerting a profound inflammatory state and exacerbating the haemodynamic derangement. This may promote in turn the development of hepatorenal syndrome, hepatic encephalopathy and other portal hypertension-related complications. Therapeutic approaches for the prevention of BT in experimental and human cirrhosis are summarized. Finally, new investigations are needed to better understand the pathogenesis and consequences of translocation by viable bacteria (able to grow in culture), or non-viable BT (detection of bacterial fragments with negative culture) and open new therapeutic avenues in patients with cirrhosis.

Gut microbiota and gastrointestinal health: current concepts and future directions

BACKGROUND

The microbial community of the human gut - the enteric microbiota - plays a critical role in functions that sustain health and is a positive asset in host defenses. In recent years, our understanding of this so-called human 'super organism' has advanced, following characterization of fecal metagenomes which identified three core bacterial enterotypes, and based on basic and clinical research into the impact and consequences of microbiota biodiversity and change on gastrointestinal disorders and diseases.

PURPOSE

This article considers current knowledge and future perspectives on the make-up and function of human gut microbiota, with a particular focus on altered microbiota and gastrointestinal disorders, nutritional influences on the gut microbiota, and the consequences for gastrointestinal health, as well as improved understanding of gut-microbiota-brain communication.

Rifaximin treatment for the irritable bowel syndrome with a positive lactulose hydrogen breath test improves symptoms for at least 3 months

BACKGROUND

While rifaximin was able to improve symptoms in patients with irritable bowel syndrome (IBS) in phase III trials, these results are yet to be repeated in phase IV studies.

AIM

To evaluate the treatment response to rifaximin in IBS patients in a phase IV trial.

METHODS

IBS patients underwent lactulose hydrogen breath testing (LHBT). LHBT-positive patients were treated with rifaximin for 14 days. Prior to treatment as well as at week 4 and 14 following the start of rifaximin treatment, patients completed a questionnaire assessing symptom severity on a Likert scale from 0 to 10.

RESULTS

One hundred and six of 150 IBS patients (71%) were LHBT-positive and treated with rifaximin. As assessed at week 4 following commencement of the therapy, rifaximin provided significant improvement of the following IBS-associated symptoms: bloating (5.5 ± 2.6 before the start of the treatment vs. 3.6 ± 2.7 at week 4, P<0.001), flatulence (5.0 ± 2.7 vs. 4.0 ± 2.7, P=0.015), diarrhoea (2.9 ± 2.4 vs. 2.0 ± 2.4, P=0.005) and abdominal pain (4.8 ± 2.7 vs. 3.3 ± 2.5, P<0.001). Overall well-being also significantly improved (3.9 ± 2.4 vs. 2.7 ± 2.3, P < 0.001). Similar improvements in IBS symptoms were obtained at week 14. Eighty-six per cent of patients undergoing repetitive LHBT (55/64) tested negative at week 4.

CONCLUSIONS

We found a high percentage of LHBT-positive IBS patients. IBS-associated symptoms (bloating, flatulence, diarrhoea, pain) were improved for a period of 3 months following 2 weeks of treatment with rifaximin. We conclude that rifaximin treatment alleviates symptoms in LHBT-positive IBS patients.

Contributions of the microbial hydrogen economy to colonic homeostasis

Colonic gases are among the most tangible features of digestion, yet physicians are typically unable to offer long-term relief from clinical complaints of excessive gas. Studies characterizing colonic gases have linked changes in volume or composition with bowel disorders and shown hydrogen gas (H(2)), methane, hydrogen sulphide, and carbon dioxide to be by-products of the interplay between H(2)-producing fermentative bacteria and H(2) consumers (reductive acetogens, methanogenic archaea and sulphate-reducing bacteria [SRB]). Clinically, H(2) and methane measured in breath can indicate lactose and glucose intolerance, small intestinal bacterial overgrowth and IBS. Methane levels are increased in patients with constipation or IBS. Hydrogen sulphide is a by-product of H(2) metabolism by SRB, which are ubiquitous in the colonic mucosa. Although higher hydrogen sulphide and SRB levels have been detected in patients with IBD, and to a lesser extent in colorectal cancer, this colonic gas might have beneficial effects. Moreover, H(2) has been shown to have antioxidant properties and, in the healthy colon, physiological H(2) concentrations might protect the mucosa from oxidative insults, whereas an impaired H(2) economy might facilitate inflammation or carcinogenesis. Therefore, standardized breath gas measurements combined with ever-improving molecular methodologies could provide novel strategies to prevent, diagnose or manage numerous colonic disorders.

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.

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.

The intestinal microbiota and chronic disorders of the gut

Mucosal surfaces of the gut are colonized by large numbers of heterogeneous bacteria that contribute to intestinal health and disease. In genetically susceptible individuals, a 'pathogenic community' may arise, whereby abnormal gut flora contributes to alterations in the mucosa and local immune system leading to gastrointestinal disease. These diseases include enteric infections, such as Clostridium difficile infection, small intestinal bacterial overgrowth, functional gastrointestinal disorders (including IBS), IBD and colorectal cancer. Prebiotics, probiotics and synbiotics (a combination of prebiotics and probiotics) have the capacity to reverse pathologic changes in gut flora and local immunity. Intestinal health and disease need to be thoroughly characterized to understand the interplay between the indigenous microbiota, the immune system and genetic host factors. This Review provides a broad overview of the importance of the intestinal microbiota in chronic disorders of the gut.

Need for a comprehensive medical approach to the neuro-immuno-gastroenterology of irritable bowel syndrome

Irritable bowel syndrome (IBS) is defined by the Rome III criteria as symptoms of recurrent abdominal pain or discomfort with the onset of a marked change in bowel habits with no evidence of an inflammatory, anatomic, metabolic, or neoplastic process. As such, many clinicians regard IBS as a central nervous system problem of altered pain perception. Here, we review the recent literature and discuss the evidence that supports an organic based model, which views IBS as a complex, heterogeneous, inter-dependent, and multi-variable inflammatory process along the neuronal-gut axis. We delineate the organic pathophysiology of IBS, demonstrate the role of inflammation in IBS, review the possible differences between adult and pediatric IBS, discuss the merits of a comprehensive treatment model as taught by the Institute of Functional Medicine, and describe the potential for future research for this syndrome.

Questioning the bacterial overgrowth hypothesis of irritable bowel syndrome: an epidemiologic and evolutionary perspective

Although studies indicate that small intestinal bacterial overgrowth (SIBO) is prevalent in irritable bowel syndrome (IBS), it remains unclear whether SIBO causes IBS. This review presents an epidemiologic and evolutionary inquiry that questions the bacterial overgrowth hypothesis of IBS, as follows. (1) Although the hypothesis may be biologically plausible, there is also a strong rationale for competing hypotheses; it is unlikely that SIBO is the predominant cause of IBS in all comers, because competing explanations are sensible and defensible. Moreover, data indicate that the test used to promulgate the SIBO hypothesis - the lactulose hydrogen breath test - may not have measured SIBO in the first place. (2) We do not have evidence of SIBO being absent before IBS symptoms, and present after IBS emerges. (3) There is not a dose-response relationship between small intestinal microbiota and IBS symptoms. (4) The relationship between SIBO and IBS is highly inconsistent among studies. (5) Many effective IBS therapies do not address SIBO at all, yet have a more favorable "number needed to treat" than antibiotics. (6) IBS does not behave like a traditional infectious disease, suggesting that microbes may not principally cause the syndrome. (7) Other factors may confound the relationship between SIBO and IBS, including proton pump inhibitors. (8) Whereas the brain-gut hypothesis is evolutionary sensible, the bacterial hypothesis is harder to defend from an evolutionary perspective. The article concludes that bacteria may contribute to some IBS symptoms, but that bacteria cannot be the only explanation, and a causal link between SIBO and IBS is not secure.

When to reconsider the diagnosis of irritable bowel syndrome

Irritable bowel syndrome (IBS) is a highly prevalent disorder characterized by nonspecific symptoms that can mimic other common medical conditions. A careful history and physical examination may reveal clues that suggest a coexisting or alternative diagnosis, such as small intestinal bacterial overgrowth or celiac disease (CD). Testing for bacterial overgrowth has limitations, but emerging data suggest that antibiotics may be of some benefit in patients with IBS with diarrhea and bloating. CD seems to have a higher prevalence in patients with IBS. Some patients with IBS may have symptomatic improvement on gluten-restricted diets, without histologic or serologic evidence of CD.

Restless legs syndrome is associated with irritable bowel syndrome and small intestinal bacterial overgrowth

BACKGROUND

Restless legs syndrome (RLS) is linked to gastrointestinal disorders. The prevalence of irritable bowel syndrome (IBS) and small intestinal bacterial overgrowth (SIBO) in RLS patients was determined.

METHODS

RLS subjects were recruited from unbiased ads that did not mention gastrointestinal symptoms. RLS diagnosis was confirmed by a neurologist and utilized the International RLS Study Group criteria. General population controls (GPC) were spouses of gastrointestinal clinic patients and were excluded for RLS. Completely healthy controls (CHC) were excluded for RLS and gastrointestinal symptoms. IBS was diagnosed by Rome II criteria. SIBO was diagnosed by the lactulose breath test (LBT).

RESULTS

There were 32 RLS subjects (23F/9M; 57 yo), 25 GPC (13F/12M; 58 yo) and 30 CHC (19F/11M; 44 yo). Twenty-nine had RLS unassociated with other GI diseases, one had celiac disease, and two had gastric resections. IBS was diagnosed in 28% of RLS subjects compared to 4% GPC (p=0.0317). SIBO was diagnosed in 69% of RLS subjects compared to 28% of GPC (p=0.0033) and 10% of CHC. Using a false positive rate of 10%, 59% of positive LBT results are associated with RLS.

CONCLUSIONS

IBS and SIBO are common in RLS. Three hypotheses developed are (a) RLS patients are selectively immunocompromised or genetically predisposed and thus more subject to SIBO; (b) SIBO leads to autoimmune changes, and subsequent auto-antibodies attack brain and/or peripheral nerves and (c) SIBO inflammation leads to increased hepcidin and CNS iron deficiency which, in turn, leads to RLS. These hypotheses bear further investigation.

Is small-bowel bacterial overgrowth an underdiagnosed disorder in children with gastrointestinal symptoms?

Small-bowel bacterial overgrowth (SBBO) has been implicated in chronic abdominal pain and irritable bowel syndrome in children. This was a retrospective study that aimed to assess the occurrence of SBBO by the lactulose breath hydrogen test in children referred primarily for investigation of carbohydrate malabsorption (n = 287). There were profiles indicative of SBBO in 16% (39/250) of hydrogen-producing children. This indicated that SBBO may be more common in children with gastrointestinal symptoms and apparent carbohydrate malabsorption than previously recognised.

Clinical predictors of small intestinal bacterial overgrowth by duodenal aspirate culture

BACKGROUND

There has been increasing interest in small intestinal bacterial overgrowth (SIBO) after reports of a link with irritable bowel syndrome (IBS), yet our understanding of this entity is limited.

AIM

Our aim was to estimate the yield of patients undergoing duodenal aspirate culture, and to identify symptoms and features that predict SIBO.

METHODS

A medical chart review of patients who had undergone duodenal aspirate culture at an academic medical centre in 2003 was performed to record clinical characteristics and culture results. The associations between aspirate results and symptoms, medical diagnoses and medication use were assessed using logistic regression.

RESULTS

A total of 675 patients had available aspirate results. Mean age of the sample was 53 (s.d. 17) and 443 (66%) were female patients. Overall, 8% of aspirates were positive for SIBO; 2% of IBS patients had SIBO. Older age, steatorrhoea and narcotic use were associated with SIBO (P < 0.05). PPI use was not associated with SIBO, but was associated with bacterial growth not meeting criteria for SIBO (P < 0.05). Inflammatory bowel disease (IBD), small bowel diverticula and pancreatitis were positively associated with an abnormal duodenal aspirate (P < 0.05), but other conditions including IBS were not associated with SIBO.

CONCLUSION

Older age, steatorrhoea, narcotic use, IBD, small bowel diverticula and pancreatitis were associated with small intestinal bacterial overgrowth based on abnormal duodenal aspirate culture results. However, no clear associations of true small intestinal bacterial overgrowth with IBS or PPI use were detected, in contrast to recent speculation.

Small intestinal bacterial overgrowth (SIBO) in irritable bowel syndrome: frequency and predictors

OBJECTIVE AND BACKGROUND

Small intestinal bacterial overgrowth (SIBO) has been implicated in pathogenesis of IBS. We aimed to study frequency and predictors of SIBO in patients with IBS.

METHODOLOGY

We included 59 consecutive patients of IBS & 37 healthy controls (HC). Evaluation for SIBO was done by glucose breath test (GBT) using 100 gm of glucose after an overnight fast. Breath hydrogen & methane concentration were noted at baseline & every 15 min after administration of glucose for a total of 3 h. Persistent rise in breath hydrogen or methane > 12 ppm above basal was considered diagnostic of SIBO.

RESULTS

Of 59 patients, 27 were diarrhoea predominant (D-IBS), 11 were constipation predominant (C-IBS) and 21 were mixed type (M-IBS). Median age of patients (34 [18-47] years) were comparable to controls (35 [20-48] years) (P = 0.21). Patient group was similar to HC in gender distribution (male 41/59 [69.5%]vs 25/37 [67.6%], P = 0.36). SIBO was more frequent in patients with IBS than HC (14/59 [23.7%]vs 1/37 [2.7%], P = 0.008). Patients with D-IBS more often had SIBO as compared to non-D-IBS (10/27 [37%]vs 4/32 [12.5%], P = 0.02). C-IBS had lowest frequency of SIBO (1/11 [9%]) among all IBS subgroups. Patients with history of bloating more often had SIBO as compared to those without this symptom (11/23 [47.8%]vs 3/36 [8.3%], P = 0.002). Among IBS patients, females more often had SIBO as compared to males (8/18 [44.4%]vs 6/41 [14.6%], P = 0.01).

CONCLUSIONS

SIBO was more frequent in patients with IBS as compared to healthy controls. D-IBS subtype, female gender & bloating were predictors of SIBO in patients with IBS.

Small intestinal bacterial overgrowth

Despite the current increase in interest in the role of the microbiota in health and disease and the recognition, for over 50 years, that an excess of colonic-type flora in the small intestine could lead to a malabsorption syndrome, small intestinal overgrowth remains poorly defined. This lack of clarity owes much to the difficulties that arise in attempting to arrive at consensus with regard to the diagnosis of this condition: there is currently no gold standard and the commonly available methodologies (the culture of jejunal aspirates and a variety of breath tests) suffer from considerable variations in their performance and interpretation, leading to variations in the prevalence of overgrowth in a variety of clinical contexts. Treatment is similarly supported by a scant evidence base and the most commonly used antibiotic regimens owe more to custom than clinical trials.

[Usefulness of lactulose breath test for the prediction of small intestinal bacterial overgrowth in irritable bowel syndrome]

BACKGROUND/AIMS

Lactulose breath test (LBT) has been used as a presumptive surrogate marker for small intestinal bacterial overgrowth (SIBO). However, recent reports suggest that abnormal LBT cannot discriminate patients with irritable bowel syndrome (IBS) from the control. Thus, the aim of this study was to evaluate the usefulness of LBT in IBS.

METHODS

LBT from 76 IBS patients, 70 functional bowel disorders (FBD), and 40 controls were examined. LBT was considered positive if (1) baseline breath hydrogen (H₂) >20 parts per million (ppm) or rise of breath H₂ >20 ppm above the baseline in <90 mins, or (2) baseline breath methane (CH₄) >10 ppm or rise of breath CH₄ >10 ppm above the baseline in <90 mins. The subjects were categorized into predominant hydrogen producers (PHP), predominant methane producers (PMP), combined producer, and both negative group based on LBT.

RESULTS

The rate of abnormal LBT in the IBS, FBD, and control group were 44.7%, 41.4%, and 40.0% respectively without significant differences. The rate of PHP or PMP was not significantly different among the IBS, FBD, and control group. When clinical characteristics were analyzed in IBS and FBD according to LBT types, IBS subtypes and symptoms were not significantly different.

CONCLUSIONS

LBT was not useful to discriminate IBS/FBD patients from the control. The assessment of SIBO by LBT in IBS should be revalidated in the future.

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.

Abnormal breath testing in IBS: a meta-analysis

BACKGROUND

Recent evidence suggests a role for enteric bacteria in the development of symptoms in subjects with irritable bowel syndrome (IBS). The concept was initially based on the common finding of an abnormal lactulose breath test to suggest the presence of small intestinal bacterial overgrowth (SIBO). Despite successful antibiotic studies based on these findings, the premise of bacterial overgrowth was met with skepticism due to the perceived inaccuracies of breath testing in humans. In this study, we conduct a systematic review and meta-analysis of the studies using breath testing in IBS subjects with comparison to healthy controls.

METHODS

A literature search was conducted to identify studies in which breath testing was conducted in subjects with IBS. Once abstract titles were identified, studies that examined breath testing in a case-control fashion were identified for paper review. After exclusion criteria were applied, the remaining papers were examined using meta-analysis, among which the prevalence of an abnormal breath test in IBS subjects was compared. Further analysis was conducted among studies with appropriate age- and sex-matched controls.

RESULTS

Eleven studies met criteria for inclusion in the meta-analysis. Although heterogeneity was identified among studies on the basis of substrate used, lactulose was the most common substrate. In pooling the 11 studies, breath testing was more often abnormal among IBS subjects than health controls (OR=4.46, 95% CI=1.69-11.80). This was further evident in more appropriately designed age- and sex-matched studies (OR=9.64, 95% CI=4.26-21.82). The overall sensitivity and specificity for breath testing in separating IBS from healthy controls was 43.6 and 83.6%.

CONCLUSIONS

This study demonstrates that the breath test findings in IBS appear to be valid. While this meta-analysis does not suggest that the breath test findings imply SIBO, the abnormal fermentation timing and dynamics of the breath test findings support a role for abnormal intestinal bacterial distribution in IBS.

Proton pump inhibitor therapy does not affect hydrogen production on lactulose breath test in subjects with IBS

BACKGROUND

Evidence suggests a role for small intestinal bacterial overgrowth (SIBO) in IBS. Recently, the question has arisen whether the lactulose breath test (LBT) is abnormal in IBS subjects due to overlapping GERD and proton-pump inhibitor (PPI) usage.

AIM

The aim of this study was to compare the prevalence of an abnormal LBT in IBS patients either receiving or not receiving PPI therapy.

METHODS

Consecutive Rome I positive IBS patients referred for LBT completed a questionnaire regarding their symptoms and medication use. All subjects then underwent an LBT. The prevalence of abnormal breath test results and hydrogen production were compared based on PPI usage.

RESULTS

Of a total of 555 (429 female) subjects, 106 (19.1%) subjects reported current PPI use. Among those on PPI, 46.2% had a positive LBT. This was not different from the 56.3% positive LBT in non-PPI subjects (OR = 0.67, CI = 0.436-1.017, P = 0.06). No differences in hydrogen parameter were seen with PPI. The average amplitude of rise (first peak) in PPI users was 28.0 +/- 35.3 ppm from baseline; in non-PPI users it was 27.5 +/- 29.1 ppm (P = 0.89). The average rise in the second peak in PPI users was 48.5 +/- 43.8 ppm from baseline; in non-PPI users, it was 49.3 +/- 37.6 ppm (P = 0.87). The time to first peak in PPI users was 56.4 +/- 23.0 min; in non-PPI users, it was 58.2 +/- 26.1 min (P = 0.58). However, among subjects receiving PPI only 7.5% had methane detection on LBT, which is significantly different from the 15.4% of subjects not taking PPI.

CONCLUSION

PPI therapy does not effect hydrogen production on lactulose breath tests in IBS patients. However, there may be an effect on methane.

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.

Bacterial overgrowth and methane production in children with encopresis

OBJECTIVES

To assess the prevalence of small intestinal bacterial overgrowth (SIBO) and methane production in children with encopresis.

STUDY DESIGN

Radiographic fecal impaction (FI) scores were assessed in children with secondary, retentive encopresis and compared with the breath test results. Breath tests with hypoosmotic lactulose solution were performed in both the study patients (n = 50) and gastrointestinal control subjects (n = 39) groups.

RESULTS

The FI scores were significantly higher in the patients with encopresis who were methane producers (P < .01). SIBO was diagnosed in 21 of 50 (42%) patients with encopresis and 9 of 39 (23%) of control subjects (P = .06). Methane was produced in 56% of the patients with encopresis versus 23.1% of the control subjects in the gastrointestinal group (P < .01). Fasting methane level was elevated in 48% versus 10.3 %, respectively (P < .01).

CONCLUSIONS

Children with FI and encopresis had a higher prevalence of SIBO, elevated basal methane levels, and higher methane production. Methane production was associated with more severe colonic impaction. Further study is needed to determine whether methane production is a primary or secondary factor in the pathogenesis of SIBO and encopresis.

Evaluating a bacterial hypothesis in IBS using a modification of Koch's postulates: part 1

It has recently been suggested that irritable bowel syndrome (IBS) symptoms are due partly to small intestinal bacterial overgrowth (SIBO). This "SIBO hypothesis" has led to the use of antibiotics to treat IBS. Koch's postulates have long been used to establish bacteria as a cause of diseases such as tuberculosis. Because SIBO is not a single organism, we use modified Koch's postulates to argue for antibiotics and an SIBO hypothesis in the pathophysiology of IBS. We show that there is evidence for SIBO, that it is culturable, that antibiotic elimination of the bacteria improves subjects clinically, and that when the bacteria return, the symptoms return. On the basis of proof of a bacterial cause of IBS, antibiotics may be a good choice of therapy.

Evaluating breath methane as a diagnostic test for constipation-predominant IBS

Studies suggest that subjects with IBS have altered gut flora. Among these findings, methane production is more commonly associated with constipation-predominant symptoms. In this study, we prospectively evaluated the role of methane as a diagnostic test. Consecutive Rome I positive IBS patients referred for a lactulose breath test were eligible to participate. After exclusion criteria, subjects completed a symptom questionnaire grading bloating, diarrhea, and constipation on a VAS scale (0-100 mm). Once completed, a physician interviewed the subjects and rated the subject accordingly, and also determined whether the patient had C-IBS, D-IBS, or neither. Subjects and physicians were blinded to the results of the breath test. The presence of methane in the breath test was compared to the results of the scoring by subjects and physicians. A total of 56 Rome I positive IBS subjects were enrolled. During breath testing, 28 subjects produced methane. Good agreement between physician's evaluation and the patient's was seen (diarrhea = 0.69; constipation = 0.69; bloating = 0.62). The severity of constipation was noted to be greater in the methane group (49.3 +/- 28.7) than in the non-methane group (25.3 +/- 31.47) (P < 0.01). In contrast, diarrhea was less severe in the methane group (12.3 +/- 21.0) than the non-methane group (36.7 +/- 32.4) (P < 0.01). Out of the 56 patients, 23 C-IBS subjects were identified by the physician. When methane was used to predict the assignment of C-IBS compared to non-C-IBS, it had a sensitivity of 91.7% and a specificity of 81.3% (OR = 47.7, CI = 9.4-232, P < 0.00001). In conclusion, methane is a potential diagnostic test for the identification of C-IBS and may guide treatment.

Use of the lactose-[13C]ureide breath test for diagnosis of small bowel bacterial overgrowth: comparison to the glucose hydrogen breath test

PURPOSE

The glucose hydrogen breath test (GHBT) is commonly used as a noninvasive test to diagnose small bowel bacterial overgrowth (SBBO) but its validity has been questioned. Our aim was to evaluate the lactose-[(13)C]ureide breath test (LUBT) to diagnose SBBO and to compare it with the GHBT, using cultures of intestinal aspirates as a gold standard.

METHODS

In 22 patients with suspected SBBO (14 male, age range 18-73 years) aspirates were taken from the region of the ligament of Treitz under sterile conditions and cultured for bacterial growth. More than 10(6) colony-forming units/mL fluid or the presence of colonic flora was defined as culture positive (c+). After oral intake of 50 g glucose and 2 g of lactose-[(13)C]ureide, end-expiratory breath samples were obtained up to 120 min. The (13)C/(12)C ratio in breath CO(2) was determined by isotope ratio-mass spectrometry and hydrogen concentration in breath was analyzed electrochemically.

RESULTS

After analyzing receiver operating characteristic curves of the LUBT results, total label recovery of >0.88% at 120 min was considered positive. The test had a sensitivity of 66.7% and a specificity of 100% to predict c+. In the GHBT, an increase of the signal of > or =12 ppm from baseline was considered positive. The sensitivity and specificity of the test were 41.7 and 44.4%, respectively.

CONCLUSIONS

The new stable isotope-labeled LUBT has excellent specificity but suboptimal sensitivity. In contrast, the standard GHBT lacks both high sensitivity and specificity. The LUBT is superior to the GHBT for detecting SBBO.

Rifaximin in the management of colonic diverticular disease

Rifaximin is a rifamycin derivative that acts by inhibiting bacterial RNA synthesis. Since it is virtually unabsorbed after oral administration, its bioavailability within the GI tract is high, with intraluminal and fecal drug concentrations largely exceeding the minimum inhibitory concentration values observed in vitro against a broad spectrum of bacteria, including Gram-positive and Gram-negative bacteria, both aerobes and anaerobes. The GI tract, therefore, represents the primary therapeutic target and the disorders in which intestinal bacteria have a pathogenic role represent the main indication. This is the case with colonic diverticular disease. As a consequence, the broad antibacterial activity of rifaximin appears to be of value in the treatment of this clinical condition. Clinical trials have provided evidence of the substantial benefit of rifaximin in diverticular disease. Indeed, available data show the efficacy of the drug in achieving symptomatic relief in patients with uncomplicated disease. A therapeutic gain of approximately 30%, compared with fiber supplementation only, can be expected after cyclic administration of rifaximin for 12 months. However, its value in the prevention of inflammatory complications of the disease needs to be further explored. Recent studies have shown some evidence of synergy between rifaximin and mesalazine and suggest that a combined treatment could be worthwhile in selected subsets of patients with diverticular disease.

Prevalence of small intestinal bacterial overgrowth in children with irritable bowel syndrome: a case-control study

OBJECTIVE

To assess the prevalence of small intestinal bacterial overgrowth (SIBO) in children affected by irritable bowel syndrome (IBS).

STUDY DESIGN

Consecutive children affected by IBS according to Rome II criteria (n = 43) were enrolled at the Gemelli Hospital, Catholic University of Rome. The control population (n = 56) consisted of healthy subjects without IBS symptoms, similar to patients for age, sex, and social background. All subjects underwent lactulose/methane breath test (LBT) to assess small intestinal bacterial overgrowth.

RESULTS

The prevalence of abnormal LBT result was significantly higher in patients with IBS (65%, 28/43) with respect to control subjects (7%, 4/56; OR 3.9, 95% CI 7.3-80.1, P < .00001). Patients with abnormal LBT showed a trend toward a worse visual analog scale score with respect to children with IBS without SIBO, but a significant statistical difference was observed only for bloating.

CONCLUSIONS

Results from this study suggest a significant epidemiologic association between SIBO and IBS in childhood. Placebo-controlled interventional studies with antibiotics used to treat bacterial overgrowth are warranted to clarify the real impact of the disease on IBS symptoms.

Small intestinal bacterial overgrowth in systemic sclerosis

OBJECTIVES

The aims of this study were to: (i) determine the prevalence of small intestinal bacterial overgrowth (SIBO) in unselected patients with SSc; (ii) assess both clinical presentation and outcome of SIBO; and (iii) make predictions about which SSc patients are at risk for SIBO.

METHODS

Fifty-one consecutive patients with SSc underwent glucose hydrogen and methane (H(2)/CH(4)) breath test. All SSc patients also completed a questionnaire for intestinal symptoms, and a global symptomatic score (GSS) was calculated. SSc patients with SIBO were given rotating courses of antibiotics (norfloxacin/metronidazole) for 3 months; glucose H(2)/CH(4) breath test was performed at 3-month follow-up.

RESULTS

The prevalence of SIBO was 43.1% in our SSc patients. After logistic regression, we identified the following risk factors for SIBO: presence of diarrhoea and constipation. Interestingly, we observed a marked correlation between values of GSS of digestive symptoms (> or =5) and the presence of SIBO (P = 10(-6)); indeed, both sensitivity and specificity of GSS > or =5 to predict SIBO were as high as 0.909 and 0.862, respectively. Finally, eradication of SIBO was obtained in 52.4% of the SSc patients with a significant improvement of intestinal symptoms.

CONCLUSION

Our study underscores that SIBO often occurs in SSc patients. We further suggest that GSS may be systematically performed in SSc patients; since we found a correlation between GSS of digestive symptoms > or =5 and SIBO, we suggest that glucose H(2)/CH(4) breath test may be performed in the subgroup of SSc patients exhibiting GSS > or =5.

Disorders of intestinal secretion and absorption

The gastrointestinal tract possesses a huge epithelial surface area and performs many different tasks. Amongst them are the digestive and absorptive functions. Disorders of intestinal absorption and secretion comprise a variety of different diseases, e.g. coeliac disease, lactase deficiency or Whipple's disease. In principle, impaired small intestinal function can occur with or without morphological alterations of the intestinal mucosa. Therefore, in the work up of a malabsorptive syndrome an early small intestinal biopsy is encouraged in conjunction with breath tests and stool analysis to guide further management. In addition, there is an array of functional tests, the clinical availability of which becomes more and more limited. In any case, early diagnosis of the underlying pathophysiology is most important, in order to initiate proper therapy. In this chapter, diagnostic procedure of malabsorption is discussed with special attention to specific disease like coeliac disease, Whipple's disease, giardiasis and short bowel syndrome. Furthermore, bacterial overgrowth, carbohydrate malabsorption and specific nutrient malabsorption (e.g. for iron or vitamins) and protein-losing enteropathy are presented with obligatory and optional tests as used in the clinical setting.

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.

Small intestinal bacterial overgrowth recurrence after antibiotic therapy

OBJECTIVES

Current treatment for small intestinal bacterial overgrowth (SIBO) is based on courses of broad-spectrum antibiotics. No data concerning SIBO recurrence are available. The aims of the present study were to investigate SIBO recurrence as assessed by glucose breath test (GBT) after antibiotic treatment and conditions associated to SIBO recurrence.

METHODS

Eighty consecutive patients affected by SIBO and decontaminated by rifaximin (1,200 mg per day for 1 wk) were enrolled. Diagnosis of SIBO was based on GBT. GBT was reassessed at 3, 6, and 9 months after evidence of GBT normalization. GBT positivity recurrence, predisposing conditions, and gastrointestinal symptoms were evaluated.

RESULTS

Ten (10/80, 12.6%), 22 (22/80, 27.5%), and 35 (35/80, 43.7%) patients showed positivity to GBT at 3, 6, and 9 months after successful antibiotic treatment, respectively. At multivariate analysis, older age (OR 1.09, 95% CI 1.02-1.16), history of appendectomy (OR 5.9, 95% CI 1.45-24.19), and chronic use of proton pump inhibitors (PPIs) (OR 3.52, 95% CI 1.07-11.64) were significantly associated to GBT positivity recurrence. All gastrointestinal symptoms significantly increased at 3, 6, and 9 months in patients with evidence of GBT positivity recurrence.

CONCLUSIONS

GBT positivity recurrence rate was high after antibiotic treatment. Older age, history of appendectomy, and chronic use of PPIs were associated with GBT positivity recurrence. Patients with evidence of GBT positivity recurrence showed gastrointestinal symptoms relapse thus suggesting SIBO recurrence.