This is a continuation of previous intervention studies exploring the impacts of a bacteriophage formulation, PreforPro, on gastrointestinal health. The purpose of this study is to determine if the PreforPro product acts synergistically with a spore-based probiotic to influence bowel habits, perceptions of gastrointestinal symptoms, microbiota composition and inflammatory and immune parameters. The proposed study will also explore a longer intervention duration than the previous studies. A secondary outcome will include measuring plasma lipids, as the proposed probiotics (B. subtilis DE111) was shown to improve total and LDL cholesterol levels in our previous study. Bacteriophages may directly influence the microbiota and intestinal environment by selectively infecting host species- in this case E. coli. Additionally, they may have indirect effects as infection of target species can open up ecological niches and/or result in assimilation of released nutrients by other commensal organisms. These phages are generally regarded as safe for human consumption and specifically infecting several strains of E. coli, including enterohemorrhagic strains and Shiga-toxin producing strains. The removal of these E. coli alters the gut environment to allow growth of more favorable bacteria. We have previously shown that PreforPro is both safe and tolerable in a human population and does not broadly disrupt the gut microbiota as would be seen with antibiotic treatment. It did not improve the survival of Bifidobacterium lactis probiotic, but did appear to amplify some of its impacts on perceived functional gastrointestinal health.

A phone screening will be conducted of all interested individuals to evaluate their eligibility. Those meeting the initial eligibility criteria will be scheduled for a clinic visit to obtain informed consent and to confirm eligibility. Consent will be obtained at the Colorado State University Food and Nutrition Clinical Research Lab (FNCRL) by a screening questionnaire and interview/assessment by the clinical coordinator. After securing consent, eligibility will be confirmed by taking anthropometric measures and participants falling within the BMI range will randomly be assigned to 1 of 3 treatment groups: (1) PreforPro+B. subtilis DE111 probiotic, (2) B. subtilis DE111 alone, or (3) maltodextrin placebo.

Visit 1 (baseline): Eligible individuals will be asked to visit the clinic at visit 1 (baseline) to provide consent and confirm eligibility, undergo sample collections (blood and stool) and analysis procedures (weight/height, hip:waist ratio, gastrointestinal symptoms/ quality of life questionnaires) and receive their stool collection container, a stool log and 3-day diet log. Participants will be schedule for their drop off visit, in which they will return to the clinic 7 days after their first visit (Visit 2, Day 0) to return their stool sample, stool log and 3-day diet record. In return, they will be provided with another stool collection kit, their treatment capsules, another stool log and 3-day diet log. At the end of the 45-day treatment period (Visit 3-Final), final blood and stool samples will be collected as well as additional analyses (such as GI questionnaires, stool logs and 3-day diet record). This means that participants will undergo screening (by phone) and make a total of three (3) visits to the clinic during the study (baseline, Day 0, Final). All blood samples will be collected at Colorado State University by trained personnel. Fecal sample collection will be performed by the study participant with collection materials provided by Colorado State University.