AIM:It has been noticed that gastroenteritis or dysenteryplays a role in pathogenesis of irritable bowel syndrome(IBS),and antibiotics can increase functional abdominalsymptoms,both of which may be partly due to intestinalflora disorders.This study was to determine the changeof gut flora of IBS,a cluster of abdominal symptoms.Because of the chronic course and frequent occurrenceof the disease,IBS patients suffered much from it.So thequality of life(Qol)of IBS patients was also evaluated inthis study.METHODS:Twenty-five Rome Ⅱ criteria-positive IBSpatients were recruited,and 25 age and gender-matchedhealthy volunteers were accepted as control.The fecalflora,including Lactobacillus,Bifidobacterium,Bacteroides,C.perfringens Enterobacteriacea and Enterococus,wereanalyzed quantitatively and qualitatively.We also calculatedthe ratio of Bifidobacterium to Enterobacteriaceae(B/E ratio)in both IBS patients and controls.In both groups,the datawere further analyzed based on age difference,andcomparisons were made between the younger and eldersubgroups.We also evaluated the quality of life(QoL)ofIBS patients and the control group using the Chinese versionof SF-36 health questionnaire.RESULTS:In IBS patients,the number of fecal Bifidobacteriumwas significantly decreased and that of Enterobacteriaceaewas significantly increased compared with that in healthycontrols(both P<0.05).The mean microbial colonizationresistance(CR)of the bowel in IBS patients was smallerthan 1,making a significant difference compared with thatin control which was more than 1(P<0.01).There was nosignificant difference in gut flora between two subgroups.While in control,the elder subgroup presented moreEnterobacteriacea than the younger one(P<0.05).Comparedwith the control group,IBS patients had significantly lowerscores on all SF-36 scales,with the exception of physicalfunctioning.However,there was no significant correlationbetween quality of life and enteric symptoms in IBS patients.CONCLUSION:There are intestinal flora disorders in IBSpatients,which may be involved in triggering the IBS-likesymptoms.IBS patients experience significant impairment in QoL,however,the impairment is not caused directly byenteric symptoms. AIM: It has been noticed that gastroenteritis or dysenteryplays a role in pathogenesis of irritable bowel syndrome (IBS), and antibiotics can increase functional abdominalsymptoms, both of which may be partly due to intestinal flora ..This study was to determine the change of gut flora of IBS, a cluster of abdominal symptoms. Cause of the chronic course and frequent occurrence of the disease, IBS patients liked much from it. So the quality of life (Qol) of IBS patients was also evaluated in study. METHODS: Twenty-five Rome II criteria -positive IBSpatients were recruited, and 25 age and gender-matchedhealthy volunteers were accepted as control.The fecalflora, including Lactobacillus, Bifidobacterium, Bacteroides, C.perfringens Enterobacteriacea and Enterococus, wereanalyzed quantitatively and qualitatively. We also calculated the ratio of Bifidobacterium to Enterobacteriaceae B / E ratio) in both IBS patients and controls. In both groups, the datawere further analyzed based on age difference, andco We also evaluate the quality of life (QoL) of IBS patients and the control group using the Chinese version of SF-36 health questionnaire .RESULTS: In IBS patients, the number of fecal Bifidobacterium was significantly decreased and that of Enterobacteriaceae was greatly increased compared with that in healthy controls (both P <0.05). The mean microbial colonization resistance (CR) of the bowel in IBS patients was smallerthan 1, making a significant difference compared with that in control which was more than 1 (P <0.01 There was nosignificant difference in gut flora between two subgroups. Whilst in elder subgroup presented moreEnterobacteriacea than the younger one (P <0.05) .Comparedwith the control group, IBS patients had significantly lowerscores on all SF-36 scales, with the exception of physicalfunctioning. However, there was no significant correlation between quality of life and enteric symptoms in IBS patients. CONCLUSION: There areintestinal flora disorders in IBS patients, which may be involved in triggering the IBS-likesymptoms. IBS patients experience significant impairment in QoL, however, the impairment is not caused directly by enteric symptoms.