Inclusion Criteria:

• Age =18 or =80, males and females.
• Diagnosed with IBS by Rome II criteria , also called "bloating"
• Normal colonic anatomy in the past 5 years as evidenced by a colonoscopy, flex sigmoidoscopy, Barium enema, Sonography, or other exam deemed acceptable by the study physician
• Normal thyroid function tests (or compensated on thyroid replacement) and negative antibody screening test for celiac disease.
• Normal blood chemistries and CBC for age, sex measured within 6 months of starting study.

Exclusion Criteria:

• Pregnant, breast-feeding, or not using approved methods of contraception (if of childbearing potential)
• Unstable medical disorder or other GI disorder (per discretion of screening physician), especially Crohn's disease, history of carcinomas of the bowel, malabsorption syndrome, intolerance to certain food types (such as lactose), functional diarrhea, and functional constipation
• Patient has undergone MAJOR abdominal surgery in the past (note: an appendectomy, for example, is not included in this definition.
• Patient has had E. coli strain M17 administered in the past six months
• History of major psychiatric disorder or substance abuse within the previous 2 years, including psychiatric illnesses requiring medication that may cause doubt in the validity of the signed Informed Consent form --
• Existing illness or medical condition that will prevent the patient from participating in the study (such as severe heart disease, insulin dependent diabetes, hyperactive thyroid gland, HIV positive, anemia, etc.)
• Participation in another clinical study during the past four weeks.
• Candidate will not be available for the next 18 weeks (2 weeks run-in, 12 weeks study, 4 weeks follow-up)
• Recent abnormal values in any routine lab tests prior to beginning the trial product, with values deviating from normal in either direction by a factor of 2.5, unless follow up test has been shown to be normal. Elevated liver function tests: aspartate aminotransferase or alanine aminotransferase >2.5 times upper limit of normal. Elevated renal function test: serum creatinine > 152.4 mmol/L (or appropriate upper cutoff per lab. Abnormal CBC indicating anemia by age and sex standards. Abnormal urinalysis (evidence of infection or albumin). Hyperthyroidism or hypothyroidism: T4 or TSH greater than or less than normal range. If previously diagnosed, disease must be managed and stable.
• Positive antibody test for celiac disease.
• Non-skin malignancy in previous 5 years
• Any use of an investigational drug within 30 days of screening period
• Any use of a probiotic supplement within 30 days of the screening period (with the exception of standard food yogurt products)
• Any use of antibiotics within 42 days of the screening period (however, candidate may wait to initiate screening exam until 42 days have lapsed since antibiotic course was completed)
• Current use of any drugs or treatments which the study physician believes has caused gastrointestinal symptoms that may be confused with or add to the symptoms of IBS.