BACKGROUND: The human microbiota comprises all microbes associated with the human body and could play an important role for transplant recipient health. It may serve as a reservoir for infectious pathogens, but also exert a protective role by preventing pathogen colonization. We tested the hypothesis that the microbiota changes in the course of renal transplantation and during associated antibiotic and immunosuppressive therapy with consequences for graft outcome.

METHODS: Urine (UR), oral (OS) and rectal (RS) swabs were collected from 60 patients receiving renal transplants: at the day of transplant and 1 and 6 months after transplant. Sample microbiota were characterized by 16S rRNA gene amplicon pyrosequencing, taxonomic assignment of sequences, and identification of statistical associations between microbiota composition and health states or time points, using standard analysis tools (CloVR-16S).

RESULTS: OS contain a diverse microbiota, mostly dominated by streptococci; RS show diverse, mostly patient-specific compositions. UR also harbor a diverse microbiota, although mostly dominated by just one, often patient-specific member (e.g., lactobacilli, enterococci, staphylococci). UR samples suggest microbiota colonization of the urinary tract independent of infection, as patient-reported infectious complications were not associated with changes in UR microbiota profiles. Post-transplant samples (at 1 month) show increases in Enterococcus (UR) and reductions in genera that include commensal and pathogenic organisms, e.g. Porphyromonas (all), Neisseria (OS), Haemophilus (OS). Patients have individual microbiota profiles before transplantation and respond differently to post-transplant medication.

CONCLUSIONS: The initial results from this ongoing study suggest a massive and systemic impact of post-transplant immunosuppressive and antimicrobial therapy on the human microbiota, including reductions in Firmicutes-Lactobacillales previously also reported in bone marrow transplant recipients. Our results suggest the need for personal microbiota profiling in order to predict transplant status and develop personalized therapeutic strategies.

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