MICROBIOTA IN ORGAN TRANSPLANTATION: THERAPEUTIC PERSPECTIVES AND MECHANISTIC INSIGHTS: Edited by Jerzy W. Kupiec-WeglinskiNew insights into the microbiome in kidney transplantationKim, Joshua S.a; Sze, Christinab; Barbar, Tarekc; Lee, John R.c,d Author Information aWeill Cornell Medicine bDepartment of Urology cDivision of Nephrology and Hypertension, Department of Medicine, Weill Cornell Medicine dDepartment of Transplantation Medicine, New York Presbyterian Hospital–Weill Cornell Medical Center, New York, New York, USA Correspondence to Dr John R. Lee, MD, Division of Nephrology and Hypertension, 525 E. 68th Street Box #3, New York, NY 10065, USA. Tel: +1 212 746 4430; e-mail: [email protected] Current Opinion in Organ Transplantation: December 2021 - Volume 26 - Issue 6 - p 582-586 doi: 10.1097/MOT.0000000000000921 Buy Metrics Abstract Purpose of review Research in the past decade has revealed important implications for the microbiome in human health. Studies have defined a distinct gut microbiota in kidney transplant recipients and have recently linked the microbiota to infectious complications, similar to the allogeneic stem cell transplant population. Recent findings In this review, we focus on the metabolism of immunosuppressive medications by the gut microbiota and on the urinary microbiome in the setting of infectious and immunological complications. We highlight seminal studies showing the role of specific gut microbiota in the direct metabolism of tacrolimus into a lesser effective immunosuppressant as well as the role of the gut microbiota in the metabolism of mycophenolic acid (MPA) glucuronide. We describe distinct urinary microbiota patterns in kidney transplant recipients with interstitial fibrosis tubular atrophy, chronic allograft nephropathy, tolerance, and bacterial and viral complications. Summary The microbiota has important implications for immunosuppressive medications and immunological outcomes in kidney transplant recipients. Further research is needed to better delineate the impact of the metabolism of tacrolimus and MPA by gut bacteria and the role of the urine microbiota in the development of immunological and infectious complications. Copyright © 2021 Wolters Kluwer Health, Inc. All rights reserved.