***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 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: BACKGROUND Evidence suggests that gut flora may play an important role in the pathophysiology of the irritable bowel syndrome ( IBS ) . We evaluated rifaximin , a minimally absorbed antibiotic , as treatment for IBS . METHODS In two identically design ed , phase 3 , double-blind , placebo-controlled trials ( TARGET 1 and TARGET 2 ) , patients who had IBS without constipation were r and omly assigned to either rifaximin at a dose of 550 mg or placebo , three times daily for 2 weeks , and were followed for an additional 10 weeks . The primary end point , the proportion of patients who had adequate relief of global IBS symptoms , and the key secondary end point , the proportion of patients who had adequate relief of IBS-related bloating , were assessed weekly . Adequate relief was defined as self-reported relief of symptoms for at least 2 of the first 4 weeks after treatment . Other secondary end points included the percentage of patients who had a response to treatment as assessed by daily self-ratings of global IBS symptoms and individual symptoms of bloating , abdominal pain , and stool consistency during the 4 weeks after treatment and during the entire 3 months of the study . RESULTS Significantly more patients in the rifaximin group than in the placebo group had adequate relief of global IBS symptoms during the first 4 weeks after treatment ( 40.8 % vs. 31.2 % , P=0.01 , in TARGET 1 ; 40.6 % vs. 32.2 % , P=0.03 , in TARGET 2 ; 40.7 % vs. 31.7 % , P<0.001 , in the two studies combined ) . Similarly , more patients in the rifaximin group than in the placebo group had adequate relief of bloating ( 39.5 % vs. 28.7 % , P=0.005 , in TARGET 1 ; 41.0 % vs. 31.9 % , P=0.02 , in TARGET 2 ; 40.2 % vs. 30.3 % , P<0.001 , in the two studies combined ) . In addition , significantly more patients in the rifaximin group had a response to treatment as assessed by daily ratings of IBS symptoms , bloating , abdominal pain , and stool consistency . The incidence of adverse events was similar in the two groups . CONCLUSIONS Among patients who had IBS without constipation , treatment with rifaximin for 2 weeks provided significant relief of IBS symptoms , bloating , abdominal pain , and loose or watery stools . ( Funded by Salix Pharmaceuticals ; Clinical Trials.gov numbers , NCT00731679 and NCT00724126 . ) BACKGROUND Traveler 's diarrhea in Thail and is frequently caused by Campylobacter jejuni . Rates of fluoroquinolone ( FQ ) resistance in Campylobacter organisms have exceeded 85 % in recent years , and reduced fluoroquinolone efficacy has been observed . METHODS Azithromycin regimens were evaluated in a r and omized , double-blind trial of azithromycin , given as a single 1-g dose or a 3-day regimen ( 500 mg daily ) , versus a 3-day regimen of levofloxacin ( 500 mg daily ) in military field clinics in Thail and . Outcomes included clinical end points ( time to the last unformed stool [ TLUS ] and cure rates ) and microbiological end points ( pathogen eradication ) . RESULTS A total of 156 patients with acute diarrhea were enrolled in the trial . Campylobacter organisms predominated ( in 64 % of patients ) , with levofloxacin resistance noted in 50 % of Campylobacter organisms and with no azithromycin resistance noted . The cure rate at 72 h after treatment initiation was highest ( 96 % ) with single-dose azithromycin , compared with the cure rates of 85 % noted with 3-day azithromycin and 71 % noted with levofloxacin ( P=.002 ) . Single-dose azithromycin was also associated with the shortest median TLUS ( 35 h ; P=.03 , by log-rank test ) .  Levofloxacin 's efficacy was inferior to azithromycin 's efficacy , except in patients with no pathogen identified during the first 24 h of treatment or in patients with levofloxacin-susceptible Campylobacter isolates , in whom it appeared to be equal to azithromycin . The rate of microbiological eradication was significantly better with azithromycin-based regimens ( 96%-100 % ) , compared with levofloxacin ( 38 % ) ( P=.001 ) ; however , this finding was poorly correlated with clinical outcome . A higher rate of posttreatment nausea in the 30 min after receipt of the first dose ( 14 % vs. < 6 % ; P=.06 ) was observed as a mild , self-limited complaint associated with single-dose azithromycin . CONCLUSIONS Single-dose azithromycin is recommended for empirical therapy of traveler 's diarrhea acquired in Thail and and is a reasonable first-line option for empirical management in general Context Using absorbed antibiotics to prevent travelers ' diarrhea is costly , has side effects , and promotes resistant organisms . Rifaximin is a nonabsorbed antibiotic approved for treating travelers ' diarrhea . Its effectiveness in preventing the condition is unknown . Contribution In this r and omized trial , 210 adults who were newly arrived in Guadalajara , Mexico , took 1 of 3 dosages of rifaximin or placebo for 2 weeks . The  rate of travelers ' diarrhea was 53.70 % in the placebo group and 14.74 % in the treated groups . Treatment caused minimal changes in fecal flora . Caution s It is uncertain whether these findings are generalizable to geographic areas where Escherichia coli is not the major pathogen . The Editors More than 50 million persons travel annually from industrialized countries to warm climates . Of these , 40 % experience diarrhea ( 1 ) , which results in an average incapacitation of 24 to 30 hours per affected person ( 2 ) . However , chronic post-travel symptoms may prove to have even greater clinical and public health importance than the temporary disability . It has been reported that 2 % to 10 % of travelers who develop diarrhea have persistent cases ( 3 , 4 ) , and more recent studies have shown that bacterial diarrhea , including that in travelers , leads to postinfectious irritable bowel syndrome in 4 % to 31 % of patients ( 5 - 10 ) . Prophylaxis with absorbed antibacterial drugs is a costeffective way to prevent travelers ' diarrhea ( 11 ) . However , this approach has not been recommended because of side effects , possible development of resistance to drugs with other important extraintestinal uses , and availability of effective therapy ( 1 , 12 ) . Rifaximin exerts antibacterial activity by inhibiting bacterial synthesis of RNA ( 13 ) . The drug has been available in Europe , Asia , and Latin America for treatment of acute bacterial diarrhea ( 14 ) and chronic intestinal conditions , including bacterial overgrowth and hepatic encephalopathy ( 15 , 16 ) , and was recently licensed in the United States for therapy for uncomplicated travelers ' diarrhea .  Rifaximin has been shown to be safe and effective for treatment of travelers ' diarrhea in Mexico , Jamaica , Guatemala , and Kenya ( 17 - 19 ) . The availability of an effective drug with less than 0.4 % absorption offered an opportunity to reexamine the use of antibacterial drugs in the prevention of travelers ' diarrhea . Methods This r and omized , double-blind , placebo-controlled study was investigator-initiated and was filed with the U.S. Food and Drug Administration . We used the CONSORT ( Consoli date d St and ards of Reporting Trials ) approach ( 20 ) to report our results . The Committees for the Protection of Human Subjects at the University of TexasHouston Health Science Center and the University of San Diego approved the study protocol . Participants Students from the United States who were at least 18 years of age and were attending classes in Guadalajara , Mexico , during July and August 2003 were eligible for enrollment within 72 hours of arrival in Mexico . During the students ' orientation period , the principal investigator of the study informed them of ways to avoid diarrhea , including safe food selection . Students lived in local homes with local families , where most meals were consumed ; expected diarrhea rates were equivalent to those for meals consumed in public restaurants ( 21 , 22 ) . Participants were young students who were free of unstable medical problems , such as type 1 diabetes mellitus , asthma requiring variable medication dosing , or active seizure disorder . Interventions Eligible participants who came to the clinic with diarrhea were r and omly assigned to the next available study number , which indicated 1 of 4 groups : rifaximin , 200 mg/d ; rifaximin , 200 mg twice daily ; rifaximin , 200 mg 3 times per day ; or a placebo tablet 3 times per day for 2 weeks . We believed that 3 times daily would be the optimal dosing of this nonabsorbed luminal antimicrobial agent because it would ensure the presence of active drug in the small bowel at the time of mealtime challenge with pathogens . In previous studies , we demonstrated that bismuth subsalicylate prevented travelers ' diarrhea when given with 3 daily meals and at bedtime , but not when given twice daily ( 23 , 24 ) . Identical-appearing placebos were given to blind the study with respect to total dose and dosing frequency . The first dose , which was active for all rifaximin groups , was given in the clinic at enrollment , and subsequent tablets were taken after daily meals . Outcomes For 3 weeks , participants maintained a daily diary of symptoms and signs rated as mild , moderate , or severe . They also noted the form and timing of all stools passed and the timing of medication taken . They were seen daily at the school clinic Monday through Friday . At the time of diarrhea or mild diarrhea , participants collected stools that were su bmi tted to our laboratory in Guadalajara , where technicians confirmed form and looked for gross blood and pathogens ( 25 , 26 ) . Participants presenting to the clinic with active diarrhea received either levofloxacin or azithromycin , which have previously been shown to be effective for this illness ( 27 ) ; these participants were withdrawn from the efficacy study but were followed for safety . Neither mild diarrhea nor occurrence of symptoms in the absence of diarrhea led to premature removal . We calculated the overall protection rate for diarrhea as follows : ( attack rate for the placebo group attack rate for the rifaximin groups combined)/(attack rate for the placebo group 100 ) . The study 's primary end point was occurrence of diarrhea , defined as passage of at least 3 unformed stools within a 24-hour period plus 1 or more of the following signs or symptoms of enteric infection : abdominal pain or cramps , nausea , vomiting , fever ( temperature 37.8 C ) , fecal urgency , passage of gross blood or mucus in stool , tenesmus , or moderate to severe increase in intestinal gas . Secondary end points included comparison of the study groups for occurrence of mild diarrhea ( defined as passage of 1 to 2 unformed stools plus a symptom ) and number of days of occurrences of moderate to severe enteric symptoms per 100 person-days of observation . Five Escherichia coli colonies from each stool sample were transferred to peptone stabs and were transported to Houston , Texas . There , the sample s were evaluated for enterotoxigenic Escherichia coli and enteroaggregative Escherichia coli by DNA probe for detection of heat-labile toxin or heat-stable toxin ( 25 ) or by HEp-2 cell assay ( 26 ) , respectively . Participants were asked to provide stool sample s after 7 and 14 days of treatment . These sample s were tested for Enterococcus species by plating sample s onto Streptococcus faecalis medium ( Bacto SF Medium , Difco Laboratories , Detroit , Michigan ) and Bacto Bile Esculin Agar ( Difco Laboratories ) and incubating them at 45.5 C for 72 hours . For sample s from half of the participants ( the workload the laboratory could h and le ) , intestinal coliform flora were quantified by using methods described elsewhere ( 28 ) . In this subset of participants , colony counts of aerobic gram-negative coliform bacilli per gram of stool were determined after plating stool on Mueller Hinton agar ( Becton , Dickinson and Co. , Sparks , Maryl and ) with and without 64 g/mL of rifaximin , the upper level of the drug for inhibition of bacterial enteropathogens ( 29 ) . We determined the minimum inhibitory concentration ( MIC ) of isolated bacterial pathogens from diarrhea cases , along with single isolates of Enterococcus and coliforms per participant from stool sample s obtained on days 7 and 14 , by using published agar dilution methods ( 29 ) and following recommendations of the National Committee for Clinical Laboratory St and ards ( now the Clinical Laboratory St and ards Institute ) , Wayne , Pennsylvania . The concentrations required to inhibit the growth of 
    Output:
    
CONCLUSIONS Rifaximin can prevent TD caused by non-invasive enteric pathogens .