Introduction: Infections are an important cause of morbidity-mortality in leukemia patients, and GI translocation is one of the most significant mechanisms. The complex microbial groups in the human microbiome are mainly understudied. Advances in sequencing strategies in the Center for Metagenomics and Microbiome Research (CMMR) are allowing the possibility of the comprehensive identification of the human GI microbiota. Hypothesis: • GI microbiota will be different between leukemia patients and healthy household controls on each study sit • GI microbiota will be different between leukemia patients from different countries. • GI microbiota will be significantly affected by chemotherapy and antimicrobial prophylaxis.