Rifaximin versus other antibiotics in the primary treatment and retreatment of bacterial overgrowth in IBS.

PURPOSE: Previous studies demonstrate improvement in IBS after antibiotic therapy, with the greatest efficacy seen with the antibiotic, rifaximin. The purpose of this study was to compare the efficacy of rifaximin in both the treatment and retreatment of IBS. METHODS: A retrospective chart review was conducted on Rome I-positive IBS patients. Charts were reviewed to evaluate all antibiotic treatments (rifaximin, neomycin, doxycycline, amoxicillin/clavulanate, and ciprofloxacin), even those predating 1 July 2004. Data collection included symptoms, breath test results (pre- and post-treatment), antibiotics used, and clinical response to individual antibiotic treatments before and after rifaximin availability in the USA. RESULTS: Out of 98 eligible charts, 84 patients received one course of rifaximin. Fifty of these (60%) had a follow-up breath test. Among these, 31 (62%) were clinical responders and 19 (38%) were nonresponders. Of 31 responders, 25 (81%) had a normal follow-up breath test compared with only 3 of the 19 nonresponders (16%) (P < 0.001). Of participants given rifaximin, 69% (58 out of 84) had a clinical response compared with only 38% (9 out of 24) with neomycin (P < 0.01) and 44% (27 out of 61) with all non-rifaximin antibiotics (P < 0.01). Rifaximin was used as retreatment on 16 occasions, and all patients improved. CONCLUSIONS: Rifaximin is more effective than other antibiotics in the treatment and retreatment of IBS.

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

Irritable bowel syndrome (IBS) is a complex, yet common diagnosis in gastroenterology. Recent data suggest the increasing importance of bacteria in the pathophysiology of IBS. Some studies have shown that IBS can be precipitated by an acute case of gastroenteritis. These pathogenic organisms may contribute to long-term gut dysfunction. In another line of effort, a growing body of evidence links IBS to the presence of excessive bacteria in the small bowel, called bacterial overgrowth. Although the means by which this is determined have been indirect, studies demonstrating the benefit of unabsorbed antibiotics suggest that reduction in gut flora is important. Further work has also examined bacterial overgrowth in the context of the various symptoms of patients with IBS. These symptom complexes include constipation, diarrhea, and alternating forms of the condition. Although this idea seems initially counterintuitive, it has been demonstrated that the fermentation of methane in the gut is associated with and can result in the slowing of intestinal transit, resulting in constipation. In this review, these topics are discussed and outlined.

Methane, a gas produced by enteric bacteria, slows intestinal transit and augments small intestinal contractile activity.

The presence of methane on lactulose breath test among irritable bowel syndrome (IBS) subjects is highly associated with the constipation-predominant form. Therefore, we set out to determine whether methane gas can alter small intestinal motor function. In dogs, small intestinal fistulae were created to permit measurement of intestinal transit. Using a radiolabel, we evaluated transit during infusion of room air and subsequently methane. In this model, small intestinal infusion of methane produced a slowing of transit in all dogs by an average of 59%. In a second experiment, guinea pig ileum was pinned into an organ bath for the study of contractile activity in response to brush strokes applied to the mucosa. The force of contraction was measured both orad and aborad to the stimulus. The experiment was repeated while the bath was gassed with methane. Contractile activities orad and aborad to the stimulus were significantly augmented by methane compared with room air (P < 0.05). In a third experiment, humans with IBS who had undergone a small bowel motility study were compared such that subjects who produced methane on lactulose breath test were compared with those producing hydrogen. The motility index was significantly higher in methane-producing IBS patients (1,851 +/- 861) compared with hydrogen producers (1,199 +/- 301) (P < 0.05). Therefore, methane, a gaseous by-product of intestinal bacteria, slows small intestinal transit and appears to do so by augmenting small bowel contractile activity.