***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
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    Input: Context Few trials have evaluated the effects of antibiotics on symptoms of the irritable bowel syndrome ( IBS ) .  Contribution In this double-blind trial , 87 patients with IBS were r and omly assigned to either rifaximin ( 400 mg 3 times daily ) or placebo for 10 days . Over a 10-week follow-up period , the rifaximin recipients reported global improvements in overall symptoms and less bloating more frequently than the placebo recipients . No major differences in abdominal pain , diarrhea , or constipation were observed between the groups . Caution s The duration of therapy and follow-up was short . Implication s Rifaximin may improve some symptoms in some patients with IBS . The Editors The irritable bowel syndrome ( IBS ) is one of the most common chronic medical conditions ( 16 ) , yet its cause is unknown . Among other contributors , alterations in gut flora have been identified as potentially important . Results of recent studies indicate that up to 84 % of patients with IBS have an abnormal lactulose breath test result , suggesting small-intestinal bacterial overgrowth ( 7 , 8) . On the basis of this concept , the antibiotic neomycin can statistically significantly improve the symptoms of IBS ( 7 , 8) . In addition , the effect of neomycin correlates with the elimination of bacterial overgrowth , as indicated by the normalization of the lactulose breath test result ( 7 , 8) . Although neomycin seems to improve symptoms , it effectively eliminates bacterial overgrowth in only about 25 % of patients with IBS ( 8) . Furthermore , side effects limit the use of neomycin . Low efficacy also applies to other antibiotics ( for example , doxycycline and amoxicillinclavulanate ) that have been previously investigated for treating bacterial overgrowth ( 9 ) . An ideal antibiotic for IBS is , arguably , one with negligible systemic absorption , minimal side effects , and high efficacy for bacterial overgrowth . Rifaximin is a gut-selective antibiotic with negligible systemic absorption ( 0.4 % ) and broad-spectrum activity in vitro against gram-positive and gram-negative aerobes and anaerobes ( 10 ) . On the basis of this broad spectrum , eradication rates with rifaximin  in bacterial overgrowth are as high as 70 % ( 11 ) . Furthermore , rifaximin has a similar tolerability profile to that of placebo and has known activity against Clostridium difficile ( 12 ) . These properties make it a good c and i date for treating a condition that is as common as IBS . Our study aim ed to determine whether the nonabsorbed antibiotic rifaximin is more effective than placebo in reducing symptoms in adults with IBS . Methods Setting and Participants Our study was conducted at the Cedars-Sinai Medical Center , Los Angeles , California , and the University of Chicago , Chicago , Illinois . We recruited patients with IBS through advertising in local media ( radio and news publications ) . We did not recruit patients from the IBS clinics of the Cedars-Sinai Gastrointestinal Motility Program to avoid enrollment of tertiary care patients . The institutional review board of both centers approved the study , and all patients provided written informed consent . Patients between 18 and 65 years of age who met Rome I criteria ( 13 ) were eligible . Exclusion criteria were the presence of underlying conditions that are known to predispose to bacterial overgrowth , including diabetes ; narcotic use ; previous bowel resection ; inflammatory bowel disease ; cirrhosis ; known bowel adhesions ; or any known chronic gastroenterological disease , such as celiac disease . We excluded patients who were taking tegaserod and antidepressants  unless these treatments were discontinued before study entry . We also excluded participants who reported taking an oral antibiotic within the previous 3 months . After participant inclusion and exclusion , we recruited 84 participants from the Cedars-Sinai Medical Center and 3 participants from the University of Chicago . We followed participants in special research clinics at both centers . R and omization and Interventions Eligible patients completed a 7-day stool diary that was based on the Bristol stool form scale ( 14 ) . Patients returned to the clinic after a 12-hour fast and completed a symptom question naire about the preceding 7 days of symptoms . We then r and omly assigned patients to double-blind treatment with 400 mg of rifaximin 3 times daily for 10 days or a matching placebo . We chose this dosage on the basis of a previous study that demonstrated the efficacy of rifaximin in bacterial overgrowth ( 11 ) . The r and omization of rifaximin versus placebo was conducted outside of Cedars-Sinai Medical Center in a 1:1 ratio into blocks of 4 patients . The allocation sequence was determined and coded at Salix Pharmaceuticals , Morrisville , North Carolina . Since this was an investigator-initiated study , the rifaximin and placebo were distributed to the Cedars-Sinai Medical Center , and nonstratified medicine and placebo were sent to the University of Chicago in groups of 4 as enrollment progressed . The medicine and placebo were prepackaged to conceal content at all times . Research personnel who were involved in product distribution were also blinded to package content . Assessment s and Follow-up After completing the 10-day course of study medication , patients immediately began another stool diary for 7 days then returned to complete a follow-up question naire and to return their pill container for a pill count to determine adherence . Patients then entered the follow-up phase , during which they completed a weekly self-administered symptom question naire at home that documented their symptoms for an additional 9 weeks ( for a total of 10 weeks of post-treatment follow-up ) . During this time , we asked participants to fax their responses to the research office . When a fax was not received on the appropriate day , research assistants called patients to ensure adherence . During this phase of study , no physician interaction occurred . During the last week of follow-up , patients completed a daily stool diary . At the end of the follow-up period , patients returned to the clinic for a final visit , which included another symptom question naire . For the initial symptom question naire , patients were asked to indicate the severity of each of 9 symptoms ( abdominal pain , diarrhea , constipation , bloating , urgency , incomplete evacuation , mucus , sense of incomplete evacuation , and gas ) on a visual analogue scale ( VAS ) ranging from 0 mm to 100 mm , with 100 mm being extreme . We used all 9 symptoms to verify IBS criteria in patients , but we assigned only diarrhea , constipation , abdominal pain , and bloating a priori as treatment end points . We asked patients to rate the severity of their symptoms on the VAS again 7 days after the completion of rifaximin treatment or placebo . Furthermore , we asked patients to provide a percentage of global improvement in their overall IBS symptoms from 0 % to 100 % . We chose global improvement since the Rome Consensus Group considers it to be the preferred end point measure in IBS treatment studies ( 15 ) . Patients then rated the severity of their symptoms on the VAS and rated global improvement again each week for 8 weeks of follow-up and at the final visit to provide a total of 10 weeks of follow-up data . Table 1 depicts the number of patients with outcomes at various time points during the study . Table 1 . Study Recruitment and Enrollment Summary At the first follow-up visit , physicians evaluated adverse events by asking patients , in an open-ended manner , whether they had experienced adverse events while receiving therapy and to elaborate on any that occurred . Although breath testing and breath methane level determinations were performed , we do not report them in our paper . Statistical Analysis We determined the number of patients for the study on the basis of the neomycin effect in a recent double-blind study for IBS on global improvement ( 8) . To detect a difference of 35 % ( SD , 50 % ) with a power of 90 % , we needed to assign 44 participants per group . Assuming a dropout rate of 10 % , we calculated that approximately 96 patients would need to be recruited . The primary end point was global improvement in IBS symptoms during follow-up . As seen in Figure 1 , data were not available for all 10 weeks of follow-up . Figure 1 . Study flow chart . We assessed the primary end point ( percentage of global improvement ) across the 10 weeks of follow-up by using an approach analogous to a repeated measures analysis of variance . Specifically , we used a mixed model with visit week ( at 10 levels ) , treatment group ( rifaximin or placebo ) , and group-by-week interaction as the fixed factors and patient as the r and om factor . The interaction and group factors were the main factors of interest in the analyses . We estimated mixed models by using the restricted maximum likelihood method . Because the global improvement percentage varied widely across week for most individuals , we considered week to be a categorical variable in the mixed model . Within-patient correlation across time was addressed by an autoregressive ( first-order ) model for the covariance structure . Missing data were mostly intermittent , and we assumed them to be missing at r and om . The normality assumption was rarely satisfied in either group at any week . However , at least 34 observations were recorded per group per week and the sample sizes were well-balanced , so we used the mixed-model analysis . We analyzed models with a single covariate ( baseline diarrhea , constipation , abdominal pain , or bloating severity score ) . The covariate models did not improve the fit nor did they change the substantive results . Hence , we presented the simpler ( no covariate ) model results . We used a similar mixed-model approach to assess the secondary end points of abdominal pain , bloating , diarrhea , and constipation . Within-patient correlation was modeled by an autoregressive covariance structure . The normality assumption was rarely satisfied for the diarrhea outcome , with a similar floor effect for the primary outcome Abstract The relationship between methanogenic flora and hydrogen ( H2 ) production is considered to be a possible confounding factor in the interpretation of hydrogen breath tests ( H2BT ) . Therefore , the present study was conducted prospect ively and included 154 IBS patients ( fulfilling Rome II criteria ) and 286 age- and -sex-matched apparently healthy controls . Each subject underwent H2BT after overnight fasting using 25 g lactose .  Methane and H2 were measured using an SC Microlyser from Quintron , USA , at baseline and every 30 min for a total of 4 h. Subjects with fasting methane concentration < 10 ppm were labeled as low methane producers ( LMP ) and > 10 ppm as predominant methane producers ( PMP ) . A rise > 20 ppm over base line in hydrogen concentration was taken as + ve hydrogen breath test . IBS and control groups included 66.78 % and 67.53 % males , respectively . Mean age in the two groups were 48.52 ± 30.54 years ( range 15–68 years ) and 45.67 ± 30.54 years ( range 15–78 years ) , respectively . Hydrogen breath test was + ve in 77/154 ( 50 % ) IBS patients and in 142/286 ( 49.65 % ) in controls ( P > 0.05 ) . It was also observed that the hydrogen breath test was −ve due to PMP in 5/77 ( 6.49 % ) of IBS patients and in 29/154 ( 20.14 % ) in controls . PMP affected lactose hydrogen breath tests in 6.49–20.14 % subjects . This effect is more apparent in apparently healthy subjects as compared to patients with IBS PURPOSE Small intestinal bacterial overgrowth ( SIBO ) may coexist with irritable bowel syndrome ( IBS ) and eradication therapy has been reported as effective in reducing IBS symptoms . Aims of this study were to : ( 1 ) Assess the clinical profiles of IBS patients , who underwent breath testing with a glucose substrate -- glucose breath test ( GBT )  ; ( 2 ) Evaluate hydrogen and methane parameters in various IBS groups ; ( 3 ) Assess the role of inhibition of gastric acid in contributing to SIBO ; ( 4 ) Investigate efficacy and safety of non-absorbable antibiotic rifamixin for eradication and symptom relief . METHODS 204 IBS patients met the ROME II criteria for IBS ( 170F & 34 M ; mean age 46.4 ; range 18 - 88 ) and underwent GBT .  8 of these patients with positive GBT were treated with rifaximin 200 mg , 4 times a day for 1 month and symptom assessment s and GBT were repeated . RESULTS 93 ( 46 % ) had a positive GBT . 68 ( 73 % ) of these 93 IBS-diarrhea dominant ( IBS-D ) , 12 ( 13 % ) were constipation dominant ( IBS-C ) and 13 ( 14 % ) IBS with alternating bowel pattern . 48 % of SIBO positive patients were receiving PPI therapy compared to 40 % of IBS patients with negative GBT . 61 ( 66 % ) produced only hydrogen , 27 ( 29 % ) methane only , and 5 ( 5 % ) both-hydrogen and methane . There were more methane producers in IBS-C then IBS-D group ( 58 % vs 28 % ) while IBS-D had more hydrogen formers ( 71 % vs 42 % ) . 8 patients with SIBO ( 7F & IM ; mean age 55 , range 31 - 85 ) received rifamixin 800 mg/day . Repeat GBT was normal in 6 ( 75 % ) 
    Output:
    
Conclusions We demonstrate that methane present on breath testing is significantly associated with constipation in both IBS and functional constipation .
These results suggest there may be merit in using breath testing in constipation .
Moreover , methane may be used to identify c and i date s for antibiotic treatment of constipation