Microbiome alterations following solid-organ transplantation: consequences, solutions, and prevention

Gut microbiota profiles and fecal beta-glucuronidase activity in kidney transplant recipients with and without post-transplant diarrhea

Post-transplant diarrhea is a common complication after solid organ transplantation and is frequently attributed to the widely prescribed immunosuppressant mycophenolate mofetil (MMF). Given recent work identifying the relationship between MMF toxicity and gut bacterial β-glucuronidase activity, we evaluated the relationship between gut microbiota composition, fecal β-glucuronidase activity, and post-transplant diarrhea. We recruited 97 kidney transplant recipients and profiled the gut microbiota in 273 fecal specimens using 16S rRNA gene sequencing. We further characterized fecal β-glucuronidase activity in a subset of this cohort. Kidney transplant recipients with post-transplant diarrhea had decreased gut microbial diversity and decreased relative gut abundances of 12 genera when compared to those without post-transplant diarrhea (adjusted p value < .15, Wilcoxon rank sum test). Among the kidney transplant recipients with post-transplant diarrhea, those with higher fecal β-glucuronidase activity had a more prolonged course of diarrhea (≥7 days) compared to patients with lower fecal β-glucuronidase activity (91% vs 40%, p = .02, Fisher's exact test). Our data reveal post-transplant diarrhea as a complex phenomenon with decreased gut microbial diversity and commensal gut organisms. This study further links commensal bacterial metabolism with an important clinical outcome measure, suggesting fecal β-glucuronidase activity could be a novel biomarker for gastrointestinal-related MMF toxicity.

Enteric dysbiosis in liver and kidney transplant recipients: a systematic review

Several factors mediate intestinal microbiome (IM) alterations in transplant recipients, including immunosuppressive (IS) and antimicrobial drugs. Studies on the structure and function of the IM in the post-transplant scenario and its role in the development of metabolic abnormalities, infection, and cancer are limited. We conducted a systematic review to study the taxonomic changes in liver (LT) and kidney (KT) transplantation, and their potential contribution to post-transplant complications. The review also includes pre-transplant taxa, which may play a critical role in microbial alterations post-transplant. Two reviewers independently screened articles, and assessed risk of bias. The review identified 13 clinical studies, which focused on adult kidney and liver transplant recipients. Patient characteristics and methodologies varied widely between studies. Ten studies reported increased an abundance of opportunistic pathogens (Enterobacteriaceae, Enterococcaceae, Fusobacteriaceae, and Streptococcaceae) followed by butyrate-producing bacteria (Lachnospiraceae and Ruminococcaceae) in nine studies in post-transplant conditions. The current evidence is mostly based on observational data and studies with no proof of causality. Therefore, further studies exploring the bacterial gene functions rather than taxonomic changes alone are in demand to better understand the potential contribution of the IM in post-transplant complications.