DNA extraction from stool samples
DNA was extracted directly from all fresh stool samples using PSP spin kit (STRATEC Inc., Berlin, Germany), following manufacturer’s instructions. Briefly, the stool samples were lysed with lysis buffer under high temperatures (95˚C) and the InviAdsorb matrix was used for eliminating undissolved particles (including PCR inhibitors) in the stool samples, followed by proteinase K enzyme to destroy some proteins and increase the purity of DNA. DNA samples were stored at -20˚C until use