Early preclinical studies suggested that intestinal microflora contribute to aGVHD and may be relapse. There is increasing evidence that use of antibiotics may have a detrimental impact on intestinal microbiota composition and, consequently, the outcome of SCT.However, effect on different antibiotic prophylaxis regimens and broad-spectrum antibiotics used during transplant and the intestinal microbiota composition and hence adverse outcomes are not known. Stool samples will be collected from patients who are undergoing SCT at:
1. preconditioning
2. at day 0 (stem cell infusion)
3. once in the period of day + 7-10 post SCT
4. once first day or second day of BMT OPD clinic visit
5. once if they develop \>=grade I GVHD
6. once at time of recovery from GVHD
