The second question to be addressed is “What are the key environmental determinants of intestinal microbiota composition?” said Dr. Peled.
“Peri-HCT exposure to broad-spectrum antibiotics is associated with lower intestinal microbial diversity,” he said. For 5,936 samples taken from 976 patients receiving allogeneic HCT, the most significant difference in diversity between those with and without broad-spectrum antibiotic exposure was seen at day 15 post transplant (P = .008).
Higher calorie intake was also associated with greater diversity (P less than .001). Higher dietary fiber intake was associated with higher abundance of Blautia, a genus considered to be a healthy commensal microorganism, Dr. Peled said.
“Conditioning intensity is associated with the magnitude of diversity loss, and with distinct microbiome configurations,” said Dr. Peled. Using 4,311 samples from 908 patients, a myeloablative conditioning regimen (n = 508) was associated with significantly less diversity when compared with reduced intensity (n = 316) and nonmyeloablative regimens (n = 84; P =.002 and P less than .001, respectively).