Patient description: The patient is a 60-year-old woman admitted to the stroke department with a recent history of a second course of intravenous antibiotics for aspiration pneumonia. She is febrile and complained of abdominal pain and diarrhea (bowel movements eight times in 3 hours, large volumes of greenish, liquid stool each time). The patient's abdomen is generally tender and distend with hyperactive bowel sounds. She is febrile (38.4°C), tachycardic (113/min) and hypotensive (80/40 mmHg). The stool samples must were positive for Clostridium difficile toxin.

Clinical trial eligibility criteria: eligible ages (years): 18.0-80.0,  Campylobacter Infections Irritable Bowel Syndrome Post Infectious IBS Cases 1. IBS by Rome III 2. No abdominal surgery (except hernia, C-section, hysterectomy, appendectomy and cholecystectomy) Post Infectious with no IBS Controls 1. No IBS by Rome III 2. No abdominal surgery (except hernia, C-section, hysterectomy, appendectomy and cholecystectomy) Post Infectious IBS Cases and Post Infectious with no IBS Controls  Prior history of IBS or inflammatory bowel disease (IBD) (Crohn's disease or ulcerative colitis), microscopic colitis or celiac disease 2. Ingestion of artificial sweeteners such as sucralose, aspartame, lactulose or mannitol 2 days before the study begins, e.g., foods to be avoided are sugarless gums or mints and diet soda 3. Ingestion of any prescription, over the counter, or herbal medications which can affect gastrointestinal transit 7 days before study begins 1. Any treatment specifically taken for IBS, including loperamide, cholestyramine, alosetron 2. Drugs with a known pharmacological activity at serotonin type 4 (5-HT4), serotonin receptor 2B (5-HT2b) or 5-HT3 receptors (e.g, tegaserod, ondansetron, tropisetron, granisetron, dolasetron, mirtazapine) 3. All narcotics (e.g, codeine, morphine, and propoxyphene, either alone or in combination) 4. Anti-cholinergic agents (e.g, dicyclomine, hyoscyamine, propantheline) 5. Ultram 6. GI preparations Anti-nausea agents (e.g, trimethobenzamide, promethazine, prochlorperazine, dimenhydrinate, hydroxyzine) Osmotic laxative agents (e.g, lactulose, sorbitol or polyethylene glycol (PEG) solutions as Miralax and Glycolax) Prokinetic agents (e.g, cisapride, metoclopramide, itopride, domperidone) 7. Antimuscarinics 8. Peppermint oil 9. Systemic antibiotics, rifaximin, metronidazole 4. Any females who are pregnant or trying to become pregnant (due to radiation exposure) 5. Bleeding disorders or medications that increase risk of bleeding from mucosal biopsies Healthy Control 1. No abdominal surgery (except hernia, C-section, hysterectomy, appendectomy and cholecystectomy) 2. No history of acute gastroenteritis, food-poisoning or travel related diarrhea within last 2 years. Healthy Control Prior history of IBS or IBD (Crohn's disease or ulcerative colitis), microscopic colitis or celiac disease 2. Ingestion of artificial sweeteners such as sucralose, aspartame, lactulose or mannitol 2 days before the study begins, e.g., foods to be avoided are sugarless gums or mints and diet soda 3. Ingestion of any prescription, over the counter, or herbal medications which can affect gastrointestinal transit 7 days before study begins 1. Any treatment specifically taken for IBS, including loperamide, cholestyramine, alosetron 2. Drugs with a known pharmacological activity at 5-HT4, 5-HT2b or 5-HT3 receptors (e.g, tegaserod, ondansetron, tropisetron, granisetron, dolasetron, mirtazapine) 3. All narcotics (e.g, codeine, morphine, and propoxyphene, either alone or in combination) 4. Anti-cholinergic agents (e.g, dicyclomine, hyoscyamine, propantheline) 5. Ultram 6. GI preparations Anti-nausea agents (e.g, trimethobenzamide, promethazine, prochlorperazine, dimenhydrinate, hydroxyzine) Osmotic laxative agents (e.g, lactulose, sorbitol or PEG solutions as Miralax and Glycolax) Prokinetic agents (e.g, cisapride, metoclopramide, itopride, domperidone) 7. Antimuscarinics 8. Peppermint oil 9. Systemic antibiotics, rifaximin, metronidazole 4. Any females who are pregnant or trying to become pregnant (due to radiation exposure) 5. Bleeding disorders or medications that increase risk of bleeding from mucosal biopsies