Effects of Pre-, Pro- & Anti-biotics on Gut Microbiota

Inclusion Criteria: * Age 18 to 39 years (male or female) * Good general health * Able to comply with study requirements and to provide informed consent * For women of childbearing potential * A negative urine pregnancy test immediately prior to starting the study treatment * Agreement to comply with approved methods of contraception during the period of active study treatment (not required during follow-up) Exclusion Criteria: * Any diagnosed autoimmune disease * History of organ transplantation * Known chronic or recurrent systemic disorder associated with immunocompromise * A history of allergy or hypersensitivity to mushroom or mushroom extract, brewer's or baker's yeast or to penicillins or cephalosporins (including amoxicillin). * History of severe allergic reaction (requiring hospital admission and/or the administration of parenteral medication or associated with dyspnoea, wheezing, hypotension, loss of consciousness). * Systemic antibacterial therapy during the 3 months prior to study enrollment * New prescription medications during the 4 weeks prior to study enrollment * Prescription or OTC medications or supplements that are known to alter gut function or microflora (i.e. acid antisecretory drugs, probiotics) during the 4 weeks prior to study enrollment * Active gastrointestinal or metabolic disease * Prior gastrointestinal surgery (apart from appendectomy or cholecystectomy) * History of chronic constipation with passage of fewer than 3 spontaneous bowel movements per week on average or chronic or recurrent diarrhea with spontaneous bowel movements more often than 3 times daily * Any condition or personal circumstance that, in the opinion of the investigator, renders the subject unlikely or unable to comply with the full study protocol.