Choosing the Best Antibiotic to Protect Friendly Gut Bacteria During the Course of Stem Cell Transplant

The purpose of this study is to see how different antibiotics affect the community of friendly bacteria existing in the intestinal tract (gut). Under normal circumstances, these friendly bacteria are not harmful and they help with normal bodily functions such as digestion. When these bacteria are absent, several complications may occur, such as infections with harmful bacteria or other inflammatory reactions, that can complicate the stem cell transplant course. Treatment with antibiotics or chemotherapy is known to kill off these friendly bacteria. In this study we compare the effects of different antibiotics on the community of friendly bacteria in the gut. For microbiota-related biomarker analysis, optional urine samples (MSKCC patients only) will be collected at baseline, 7 +/-2 days after initiation of antibiotic therapy, and on post-transplant days +28, +56 and +100 (+/- 7days).