design: Total DNA was extracted from stool samples following the manufacturers protocols using either the FastDNA Spin Kit (MP Biomedicals) or the Maxwell RSC PureFood GMO and Authentication Kit (Promega). The V3V4 regions of the 16S rRNA gene were amplified by polymerase chain reaction (PCR) using primers 341F (CCTACGGGNGGCWGCAG) and 805R (GACTACHVGGGTATCTAATCC). PCR amplification conditions included an initial denaturation at 95C for 3 minutes, followed by 25 cycles of denaturation at 95C for 30 seconds, primer annealing at 55C for 30 seconds, and extension at 72C for 30 seconds, with a final elongation at 72C for 5 minutes. PCR products were verified using 1% agarose gel electrophoresis and visualized on a Gel Doc system (Bio-Rad). Amplicons were purified, and short non-target fragments were removed with the ProNex Size-Selective Purification System (Promega). The quality and size of the PCR products were assessed using a Bioanalyzer 2100 (Agilent) with a DNA 7500 chip. The pooled amplicons were sequenced using an Illumina MiSeq system at CJ Bioscience, Inc., following the manufacturers instructions.