Spiked stool samples, clinical stool samples, and swabs were extracted with the QIAamp Stool DNA Mini kit (Qiagen, Valencia, CA), after a bead beating step and 95°C incubation. For stool specimens, 200 mg of raw stool was first lysed with QIAamp ASL buffer, beaten for 2 min with 212 to 300-μm glass beads (Sigma, St. Louis, MO), and incubated at 95°C for 5 min. The samples were centrifuged at full speed for 1 min to pellet stool particles, then 400 μl of ASL lysate were extracted and eluted in 200 μl of elution buffer following the manufacturer’s instructions. For swabs, the dry swab was mixed with the lysis buffer and glass beads, then subjected to bead beating directly and extracted following the same procedure as that for stool. Two extrinsic controls, Phocine Herpesvirus (PhHV) and bacteriophage MS2, were spiked into lysis buffer to monitor extraction and amplification efficiency. For comparison of extraction methods, one aliquot of each sample was extracted with QIAamp Stool DNA Mini kit and another aliquot was extracted with the QIAamp Viral RNA mini kit (Qiagen) or QuickGene RNA Tissue kit (FujiFilm, Tokyo, Japan). During all extractions an extraction blank was incorporated to monitor for lab contamination.
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