Alteration of the intestinal microbiota by broad-spectrum antibiotic use correlates with the occurrence of intestinal graft-versus-host disease.

•Broad-spectrum antibiotic use correlates with intestinal graft-versus-host diseases.•Broad-spectrum antibiotic use reduces intestinal bacterial diversity.•Loss of bacterial diversity affects the occurrence of intestinal GVHD.•Broad-spectrum antibiotic use has effects on circulating immune cell recovery.