Depletion of fecal microbiota is a key factor in the development of antibiotic-associated bone marrow suppression. (A) Granulocytes and (B) CD4:CD8 ratio were quantified by flow cytometry for controls (Ctrl), antibiotic-treated mice (Abx), and mice treated with antibiotics plus fecal microbiota transfer (Rescue). Results are compiled from 2 independent experiments (n = 5-17 per group). (C) Granulocytes and (D) CD4:CD8 ratio were quantified by flow cytometry for controls and antibiotic-treated SPF and germ-free (GF) mice. Results are representative of a single experiment (n = 3-5 per group per experiment). The graphs show mean + SEM, statistical significance was determined by Student t test. *P < .05, **P < .01, ***P < .001.