The Protective Immune Response to Attenuated Enterotoxigenic Escherichia Coli Infection

Inclusion Criteria: In order to be eligible to participate in this study, a subject must meet all of the following criteria: 1. Male 2. Age between 18 and 55 years. 3. BMI ≥18.5 and ≤30.0 kg/m2. 4. Healthy as assessed by the NIZO health questionnaire. 5. Ability to follow Dutch verbal and written instructions. 6. Availability of internet connection. 7. Signed informed consent. 8. Willing to accept disclosure of the financial benefit of participation in the study to the authorities concerned. 9. Willing to accept use of all encoded data, including publication, and the confidential use and storage of all data for at least 15 years. 10. Willing to comply with study procedures, including collection of stool and blood samples. 11. Willingness to abstain from high calcium containing products. 12. Willingness to abstain from alcoholic beverages three days before, during and for 4 days after diarrheagenic E. coli challenge. 13. Willingness to abstain from medications that contain acetaminophen, aspirin, ibuprofen, and other non-steroidal anti-inflammatory drugs, (OTC) antacids and antimotility agents (eg, loperamide) on the three days before, during and for 4 days after diarrheagenic E. coli challenge. 14. Willingness to abstain from probiotics and prebiotic/fibers starting from runin and during the whole study. 15. Willingness to give up blood donation starting at run-in and during the entire study. Exclusion Criteria: A potential subject who meets any of the following criteria will be excluded from participation in this study: 1. Acute gastroenteritis in the 2 months prior to inclusion 2. Any confirmed or suspected immunosuppressive or immunodeficient condition including human immunodeficiency virus infection (HIV). 3. Disease of the GI tract, liver, gall bladder, kidney, thyroid gland (self-reported), except for appendicitis. 4. History of microbiologically confirmed ETEC or cholera infection within 3 years prior to inclusion. 5. Symptoms consistent with Travelers' Diarrhea concurrent with travel to countries where ETEC infection is endemic (most of the developing world) within 3 years prior to inclusion, OR planned travel to endemic countries during the length of the study. 6. Vaccination for, or ingestion of cholera within 3 years prior to inclusion, including studies at NIZO. 7. Occupation involving handling of ETEC or Vibrio cholerae currently, or within 3 years prior to inclusion. 8. Vaccination for, or ingestion of ETEC or E coli heat labile toxin, including E. coli challenge studies at NIZO. 9. Evidence of current excessive alcohol consumption (\>4 consumptions/day or \>20 consumptions/week) or drug (ab)use, and not willing/able to stop this during the study. 10. Known allergy to the following antibiotics: ciprofloxacin, trimethoprim, sulfamethoxazole, and penicillins. 11. Reported average stool frequency of \>3 per day or \<1 per 2 days. 12. Use of antibiotics, (during 6 months prior to inclusion), norit, laxatives, cholestyramine, antacids H2 receptor antagonists or proton pump inhibitors (during 3 months prior to inclusion). 13. Use of immunosuppressive drugs (e.g. cyclosporine, azathioprine, systemic corticosteroids, antibodies). 14. Vegans. 15. Mental status that is incompatible with the proper conduct of the study. 16. Not having a general practitioner, not allowing disclosure of participation to the general practitioner or not allowing to inform the general practitioner about abnormal results. 17. Participation in any clinical trial including blood sampling and/or administration of substances starting 1 month prior to study start and during the entire study. 18. Personnel that is part of the study team at NIZO, their partner and their first and second degree relatives.