Effects of prebiotics, probiotics, and antibiotics on the microbiota in stem cell transplant patients. Diet and antibiotics interact with host factors including the patient’s underlying malignancy, prior chemotherapy, and conditioning regimens to affect the composition of the microbiota. Antibiotics in this model can lead to a decrease in microbiota diversity and result in the development of dysbiosis, diarrhea, GVHD, and infection. The microbiota can be returned to a more symbiotic state representative of a prior healthier state of homeostasis with the use of prebiotics and probiotics that improve microbiota diversity