the postinfectious irritable bowel syndrome is characterized by the sudden onset of symptoms mentioned in the diagnostic criteria for irritable bowel syndrome ( with rome iv criteria being the most recently defined ) . they appear following an episode of acute infectious gastroenteritis characterized by two or more of the following symptoms and findings : diarrhea , vomiting , fever and a positive stool culture result . the human gastrointestinal ( gi ) microbiota is a rich and dynamic community inhabited by approximately 1014 bacteria , most of which uncultivated yet in the laboratory ( zoetendal et al , 2006 ) . multiple theories linking irritable bowel syndrome etiology with the intestinal microbiota have been proposed , which , together with the discovered irritable bowel syndrome - associated gi microbiota alterations , imply that bacteria could play a part in irritable bowel syndrome etiology . the overall microbial community from fecal samples of irritable bowel syndrome subjects has been analyzed applying denaturing gradient gel electrophoresis ( dgge ) , microarray ( hitcip and phylochip ) , and sequencing ( conventional sanger sequencing and 2nd generation 454 pyrosequencing ) . these methods are capable of detecting the unculturable species in the microbiota , although they have restrictions due to primer and probe dependency and technical biases . the possibility to gain a non - restricted overview with sequencing , to design targeted primers and probes for applications based on pcr or hybridization is the main advantage . the differences in the intestinal microbiota between irritable bowel syndrome patients and healthy controls ( hcs ) have mostly been studied using fecal material , known as the most accessible source of the gi microbiota . developed a study regarding the alteration in composition and diversity of the intestinal microbiota in patients with diarrhea - predominant irritable bowel syndrome . therefore , fecal dna was isolated from 23 d - irritable bowel syndrome patients and 23 healthy controls ( hc ) . variable regions v1v3 and v6 of the 16s rrna gene were amplified from all samples . pcr products were sequenced using 454 high throughput sequencing . using quantitative insights into microbial ecology pipeline the composition , richness and diversity of microbial communities were determined and compared between d - irritable bowel syndrome and hc . the results were the fact that the contribution of bacterial groups to the composition of the intestinal microbiota differed between d - irritable bowel syndrome and hc . d - irritable bowel syndrome patients had significantly higher levels of enterobacteriaceae ( p=0.003 ) and lower levels of faecalibacterium genera ( p=0.04 ) compared to hc . beta - diversity values demonstrated significantly lower levels of unifrac distances in hc compared to d - irritable bowel syndrome patients . the richness of 16s rrna sequences was significantly decreased in d - irritable bowel syndrome patients ( p<0.04 ) . their 16s rrna sequence data demonstrated that a community - level intestinal microbiota in d - irritable bowel syndrome is associated with significant increase , which is detrimental and decreases beneficial bacterial groups , and a reduction in microbial richness . suggest that altered intestinal microbiota contributes to the symptoms of irritable bowel syndrome through increased levels of organic acids . in fecal samples , irritable bowel syndrome patients had significantly higher numbers of veillonella and lactobacillus than healthy controls . furthermore , in irritable bowel syndrome patients with high acetic acid or propionic acid levels the symptoms were more severe , they presented negative emotions and an impaired quality of life . the results are in accordance with the concept that the gut microbiota interacts with higher brain centers that influence the sensory , motor and immune system of the gut . the bacterial overgrowth in the small intestinal observed in a subset of irritable bowel syndrome patients shows quantitative changes in the small bowel microbiota . data are lacking on qualitative changes in the gut microbiota in irritable bowel syndrome patients . the concepts identified here may lead to the development of novel therapeutic strategies for irritable bowel syndrome using manipulation of the intestinal microbiota . dysbiosis of the intestinal microbiota in irritable bowel syndrome has been detected on several levels : the overall community appears to be less diverse with more variation between individuals and overtime . these phenomena may reduce the resilience of the microbiota to external stressors , and both trigger and sustain functional aberrations in the gut . in addition to overall dysbiosis , specific bacterial groups are either elevated ( lactobacillus , veillonella , ruminococcus , enterobacteriaceae , aerobes group , s. aureus ) or reduced ( bifidobactrium , b.catenulatum , bacteroides ) in irritable bowel syndrome , with the exception of bifidobacteria . treatment is frequently symptom directed rather than curative and includes agents prescribed for the treatment of irritable bowel syndrome- d . it follows therefore that reducing fiber intake might be beneficial in d - irritable bowel syndrome . opiates : codeine or loperamide inhibit rapid transit whatever the cause and also inhibit secretions . although loperamide is effective in improving stool consistency it is less effective in controlling pain in irritable bowel syndrome . antispasmodics , such as the anticholinergic agent hyoscyamine , reduce intestinal the activity of smooth muscle . tricyclic antidepressants : these have multiple actions with anti - histaminic , anti - muscarinic as well as serotonin reuptake inhibition . tricyclics have been shown in large clinical trials to reduce pain , nausea and diarrhea in irritable bowel syndrome . 5ht3-antagonists : alosetron slows colonic transit and improves stool consistency and frequency in d - irritable bowel syndrome . side effects include constipation which can be severe , and rarely ischemic colitis which caused a temporary suspension of the drug . in an outbreak of waterborne giardiasis where 1300 subjects were diagnosed , with g. lamblia 139 patients continued to have abdominal symptoms of whom two of three had negative stool microscopy and culture . investigated visceral hypersensitivity in patients with persisting abdominal symptoms after g. lamblia infection ; they also assessed the effect of 5ht(3)-antagonist ondansetron . patients with g. lamblia  induced gastrointestinal symptoms developed both functional dyspepsia and irritable bowel syndrome . ondansetron ( 5-ht(3 ) antagonist ) , did not improve gastric emptying , drinking capacity , or symptoms except nausea . 5ht4 agonists : tegaserod is the only one agent marketed in this class , and it stimulates colonic transit in both healthy volunteers and patients with constipated irritable bowel syndrome . it is successful in improving global symptoms , it softens the stool consistency , increases the frequency of bowel movement , and reduces the symptoms of bloating ( nnt = 1012 ) . cholestyramine is useful in diarrhea due to bile salt malabsorption   which may develop following acute gastroenteritis . several studies have documented that postinfectious irritable bowel syndrome can respond to cholestyramine   which is nevertheless rather poorly tolerated owing to its unpleasant taste in its current formulation . antibiotics : the diagnostic criteria for irritable bowel syndrome include symptoms ( bloating , abdominal pain and altered bowel habits ) are similar to those experienced by subjects with small intestinal bacterial overgrowth ( sibo ) . studies have demonstrated an association between sibo and irritable bowel syndrome using breath testing techniques . when galatola et al .   performed 14c - xylose breath tests on subjects with a number of gastrointestinal disorders , the prevalence of abnormal breath tests demonstrating sibo was 56% and 29% in diarrhea and constipation predominant irritable bowel syndrome , respectively . . however , nayak et al .   demonstrated that irritable bowel syndrome subjects treated with metronidazole were significantly better than placebo - treated patients . this suggested that bacteria could play a part in the symptomatology of the irritable bowel syndrome . pimentel et al .   showed that eradication of sibo improves the gastrointestinal symptoms of irritable bowel syndrome . the antibiotics used in the treatment of sibo in the 47 subjects were neomycin , ciprofloxacin , flagyl and doxycycline , 710 days . although efficacy data for antibiotic prophylaxis in the prevention of acute bacterial diarrhea are limited , antibiotics have demonstrated efficacy for treating bacterial diarrheal illnesses and reducing the duration of illness by 12 days compared with placebo or no intervention . even though fluoroquinolones have become standard therapy for the treatment of travelers diarrhea , in double - blind , placebo - controlled , randomized , and comparative studies rifaximin 6001,800 mg / day for 35 days has also been shown to be effective treatment . the efficacy of antibiotics for the treatment of postinfectious irritable bowel syndrome has not been specifically evaluated , but research suggests that antibiotics may be effective in treating a subset of patients with irritable bowel syndrome . prophylaxis aimed at preventing or early treatment of acute bacterial diarrhea may reduce the risk of postinfectious irritable bowel syndrome development by reducing the occurrence , duration , and severity of the chronic inflammation and mucosal alterations believed to play a role in disease persistence . several agents , including bismuth subsalicylate and antibiotics ( e.g. , fluoroquinolones and rifaximin ) , have been evaluated for the prevention of travelers diarrhea . bismuth subsalicylate is not as effective as antibiotics in preventing diarrheal illness , and concerns about bacterial resistance may limit the use of fluoroquinolones prophylactic . probiotics can restore the intestinal microbiota in patients with irritable bowel syndrome and result in an improvement of postinfectious irritable bowel syndrome in animal models . fecal microbiota transplantation ( fmt )  can be probably more beneficial , as donated feces , in a sense , are the ultimate human probiotic . in a case series of 55 patients with irritable bowel syndrome and ibd treated with fmt , cure was reported in 20 ( 36% ) , decreased symptoms in nine ( 16% ) and no response in 26 ( 47% ) patients . in another series , 45 patients with chronic constipation were treated with colonoscopic fmt and subsequent fecal enema infusions , 89% of whom ( 40 of 45 patients ) reported relief in abdominal pain , bloating and defecation , immediately after the procedure . normal defecation , without using laxatives , persisted in 18 of 30 patients ( 60% ) contacted 919 months later . treatment of recurrent clostridium difficile infection ( cdi ) with antibiotics leads to recurrences in up to 50% of patients . mattila e et al . investigated the efficacy of fecal transplantation in treatment of recurrent cdi . persistent or recurrent symptoms and signs were defined as clinical failure and a need for new therapy . symptoms resolved in all patients who did not have strain 027 cdi during the first 12 weeks after fecal transplantation . of 36 patients with 027 cdi , 32 ( 89% ) had a favorable response ; all 4 nonresponders had a pre - existing comorbidity or serious condition , caused by a long lasting diarrheal disease and subsequently died of colitis . during the first year after transplantation , 2 patietnts were treated successfully with another fecal transplantation and 2 with antibiotics for cdi ; 4 patients with an initial favorable response after receiving antibiotics for unrelated causes had a relapse . within 1 year after transplantation 10 patients died of unrelated illnesses . fecal transplantation through colonoscopy seems to be an effective treatment for recurrent cdi and also for recurrent cdi caused by the virulent clostridium difficile 027 strain . patients diagnosed with irritable bowel syndrome ( ibs ) have observed the association between specific foods with worsening of symptoms . because of limited data and guideline consensus and also because of the nuances of symptoms associated with ibs subtypes , clinical guidance for doctors and nurse practitioners can be challenging . by addressing the relevance of diet for symptom alleviation , doctors and nurse practitioners are able to better support patients and collaborate with dieticians to improve symptom management . there is no convincing evidence that gluten causes the new and debated diagnosis of non - coeliac gluten sensitivity ( ncgs ) , as well as there is no evidence that ibs patients suffer from food allergy or food intolerance . patients with ncgs appear to be ibs patients who are self - diagnosed and self - treated with a gluten - free diet . the consumption of the poorly absorbed fermentable oligo- , di- , monosaccharide and polyols ( fodmaps ) and insoluble fiber might be a trigger in ibs symptoms . fodmaps and insoluble fiber increase the osmotic pressure in the large - intestine lumen and provide a substrate for bacterial fermentation , on reaching the distal small intestine and colon . poor fodmaps and insoluble fibers diet reduces the symptom and improve the quality of life in ibs patients . low intake in fodmaps can change favorably the intestinal microbiota and restores the abnormalities in the gastrointestinal endocrine cells . five gastrointestinal endocrine cell types that produce hormones regulating appetite and food intake are abnormal in ibs patients . based on these hormonal abnormalities , it is expected that ibs patients might have increased food intake and body weight gain . the link between obesity and ibs is not fully studied . individual dietary guidance for intake of poor fodmaps and insoluble fibers diet in combination with probiotics intake and regular exercise is to be recommended for ibs patients . a diet with reduced content fosmaps has been reported to be effective in the treatment of patients with irritable bowel syndrome ( ibs ) . bhn et al . compared the effects of a diet low in fodmaps with traditional dietary advice in a randomized controlled trial of patients who met rome iii criteria for ibs and reached to the conclusion that a diet low in fodmaps reduces ibs symptoms as well as traditional ibs dietary advice . approximately 70% of ibs patients point at certain foods as triggers for their symptoms . to help identify potential trigger foods zia et al . evaluated the feasibility and usability of a novel food and symptom journal app , specifically designed for patients with ibs . the results were that the app appeared to be a feasible and usable tool for ibs patients . the findings were that most ibs patients have food triggers and that these vary by individual . future studies can explore whether individualized dietary changes guided by an app can result in ibs symptom improvement . rome iv recognize further the postinfectious ibs as a specific entity , according to the multidimensional clinical chronic mucosal inflammation triggered by enteric infection may underlie persistent bowel symptoms in patients who develop postinfectious irritable bowel syndrome . antimicrobials , such as rifaximin , have shown potential benefit in the prevention and treatment of acute bacterial illness in international travelers , as well as in the treatment of established irritable bowel syndrome . combining a diet low in fodmaps with traditional ibs dietary advice , might further reduce symptoms of ibs .