Inclusion Criteria:  Provision of signed written informed consent, Aged between 21-65 years of age, Chinese, Malay or Indian ancestry through three generations, Body Weight ≥ 50kg, Body Mass Index (BMI) of 18.5 to 29.9 kg/m2, inclusive, Clinical laboratory assessment results within normal limits, unless the deviation is considered not clinically significant by the investigator, Regular stool every 1-2 days, Satisfactory medical assessment as assessed by physical examination, medical history, and normal laboratory values or minor variations that are not clinically significant, Ability to communicate with the investigator and to understand and comply with all requirements of study participation. Both male and female participants (with child-bearing potential) and their partners have to practise contraception throughout the duration of the study.  Exclusion Criteria:  Any acute illness within 14 days of first dosing, unless otherwise approved by the PI, History or evidence of clinically significant hepatic, renal, cardiovascular, respiratory, gastrointestinal, immunosuppressive or metabolic disorders, any cancer types, Declare themselves positive for HIV or viral hepatitis (Hepatitis A, B, C), Treatment within the previous 3 months with antibiotics (subjects are to inform study staff should they be prescribed antibiotics during the course of the study) Treatment with any prescription or over-the-counter medications, complementary health products, or herbal supplements within 28 days of first dosing, Consumption of probiotics or lactobacillus-containing products e.g. Yakult, Vitagen or Yogurt within 4 weeks of first dosing unless approved by the PI, Abnormal biochemistry indicators, unless certified as not clinically significant, Poor peripheral venous access, Irregular bowel habits or complains of constipation problem, Pregnancy or lactation, Known allergic reactions to rifaximin, PEG or VSL#3, History of drug/alcohol abuse, Involvement in the planning or conduct of this study.