Serial Blood Microbiome Profiles in Kidney Transplant Recipients Reveal Evidence of Circulating Gut and Non‐Gut Derived Microbial DNA

ABSTRACT Background In this study, we sought to investigate the utility of 16S rRNA gene sequencing of whole blood in kidney transplant recipients and to assess a link between the gut microbiota and the blood microbiota. Methods We recruited 63 kidney transplant recipients who provided 163 whole blood specimens over the first 140 days after transplantation. We profiled the blood microbiome using 16S rRNA gene sequencing of the V4‐V5 hypervariable region. We additionally evaluated the gut microbiota via metagenomic sequencing in a subset of kidney transplant recipients who had matched blood specimens. Results We generated a median of 19 959 sequences per blood specimen. We discovered that most whole blood microbiome profiles consisted of mitochondrial DNA (mean relative blood abundance greater than 99%) with minimal microbial DNA detected. Out of the 163 blood specimens, 83 (51%) had detectable microbial 16S rRNA sequences and there were 92 distinct taxa detected at the genus level. Among the 51 kidney transplant recipients, blood microbial 16S sequences were persistently detected in 10 kidney transplant recipients over time, intermittently detected in 29 kidney transplant recipients over time, and not detected in 12 kidney transplant recipients over time. Among 76 matched blood–fecal specimens, 9 blood specimens had detectable gut microbial 16S sequences, which were also detected in 3 of the 9 fecal specimens. Conclusion Our study finds minimal detection of bacterial DNA in the blood microbiome in kidney transplant recipients and evidence of gut bacterial DNA in the bloodstream of kidney transplant recipients. image