Urobiome composition after renal transplantation: an exploratory study

The urobiome of renal transplant recipients is poorly defined. The purpose of this study was to investigate whether there are characteristic changes in the urobiome between pre- to post-transplant states, at varying degrees of post-transplant allograft function, and between those with acute T-cell mediated rejection (TCMR) versus a non-rejector cohort.

41 patients who consented to have urine stored in our transplant biobank were included in this study: 1) Rejectors (n = 10 pts: 6 borderline, 1 Banff IA, 3 Banff IIA TCMR, mean age: 47.4 ± 12.4 yrs); 2) Women (n = 16 pts; mean age: 49.3 ± 17.3 yrs); 3) Men (n = 15 pts, mean age: 47.5 ± 17.2 yrs). Urine was collected via mid-stream clean-catch technique prior to transplant (n = 21), at the time of TCMR (n = 9; within 1 month of transplant), 1-month (n = 15), and 3-months post-transplant (n = 38). Samples were processed and stored at -80 [Formula: see text] until 16S rRNA sequencing. Alpha diversity, beta diversity, and differential abundance analysis was performed.

The urobiome was altered post-transplant, with rejectors gaining Corynebacterium and Pseudomonas at time of rejection, and non-rejectors gaining Lactobacillus among other taxa. Within individuals, post-transplant urobiome composition was ~ 75% dissimilar from pre-transplant (p < 0.001). Urobiome composition differed by sex (p = 0.002), but not by age. Differential abundance analysis based on 3-month post-transplant eGFR revealed consistent loss of Lactobacillus with decreased renal function.

Our results suggest that renal transplantation has a strong impact on individual urobiome composition, but not diversity, and microbial imbalance may be associated with acute rejection and post-transplant renal function. Our findings indicate a need for further research into the urobiome during renal transplantation to elucidate its potential as a biomarker of and/or contributor to post-transplant allograft health.