This is a pilot study designed to investigate the alterations in the gut microbiome that occur during the course of kidney transplantation, liver transplantation, allogeneic hematopoietic stem cells and mesenchymal stem cells transplantation in association with the clinical outcomes.

This is a pilot study designed to investigate the dynamic changes in the intestinal microbiome that occur during the course of kidney transplantation, liver transplantation, allogeneic HSCs and mesenchymal stem cells transplantation. Four patient cohorts will be followed. Cohort A: patients receiving kidney transplantation. Cohort B: patients receiving hematopoietic stem cells transplantation. Cohort C: patients receiving mesenchymal stem cells transplantation. Cohort D: patients receiving liver transplantation. Included participants are defined as patients with at least three analyzable stool samples including a baseline sample before the transplantation.

Inclusion Criteria:

• Participants enrolled into kidney transplantation or HSCs transplantation or MSCs transplantation or liver transplantation programs with fecal samples collected over the course of their initial transplant hospitalization.
• Be willing and able to provide written informed consent for the study.

Exclusion Criteria:

• Patients were excluded from the study if their first sample was not collected prior to the start of transplantation procedure.
• Samples were excluded from the analysis if they were not aliquoted and stored frozen within 24 hours of collection.

Recruitment will include both patients with planned transplantations as well as recipients in urgent need of transplantation. The study coordinator may identify potential participants via direct referral from a treating physician, review of transplant lists and schedules.