Stool Sample Collection and Analysis

The stool sample collection followed our previous protocol^{32 (link)}. Subjects were instructed to collect stool samples by trained research nurses. Subjectswere instructed to collect stool samples at home, and labeled postage-paid envelopes were provided to ship the samples to the authors’ institute. The subjectswere guided to drop the sealed envelopes at the nearby USPS drop box at their earliest convenience after sample collection. Anonymous tracking barcodes were also affixed on the envelopes to track the delivery. The stool samples were aliquoted into small screw cap vials and stored in a −80 °C freezer once arriving at the applicant’s institution. The fecal DNA was extracted, and the 16S rRNA V4 tags were amplified and sequenced by Illumina MiSeq. 2000 at the University of Connecticut Microbial Analysis, Resources, and Services following our previous protocol^{33 (link)}.