Comprehensive description of blood microbiome from healthy donors assessed by 16S targeted metagenomic sequencing

Transfusion. 2016 May;56(5):1138-47. doi: 10.1111/trf.13477. Epub 2016 Feb 10.


Background: Recent studies have revealed that the blood of healthy humans is not as sterile as previously supposed. The objective of this study was to provide a comprehensive description of the microbiome present in different fractions of the blood of healthy individuals.

Study design and methods: The study was conducted in 30 healthy blood donors to the French national blood collection center (Établissement Français du Sang). We have set up a 16S rDNA quantitative polymerase chain reaction assay as well as a 16S targeted metagenomics sequencing pipeline specifically designed to analyze the blood microbiome, which we have used on whole blood as well as on different blood fractions (buffy coat [BC], red blood cells [RBCs], and plasma).

Results: Most of the blood bacterial DNA is located in the BC (93.74%), and RBCs contain more bacterial DNA (6.23%) than the plasma (0.03%). The distribution of 16S DNA is different for each fraction and spreads over a relatively broad range among donors. At the phylum level, blood fractions contain bacterial DNA mostly from the Proteobacteria phylum (more than 80%) but also from Actinobacteria, Firmicutes, and Bacteroidetes. At deeper taxonomic levels, there are striking differences between the bacterial profiles of the different blood fractions.

Conclusion: We demonstrate that a diversified microbiome exists in healthy blood. This microbiome has most likely an important physiologic role and could be implicated in certain transfusion-transmitted bacterial infections. In this regard, the amount of 16S bacterial DNA or the microbiome profile could be monitored to improve the safety of the blood supply.

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Blood / microbiology*
  • Blood Donors
  • Blood Safety
  • DNA, Bacterial / blood
  • DNA, Bacterial / isolation & purification*
  • DNA, Ribosomal
  • France
  • Healthy Volunteers
  • Humans
  • Metagenomics / methods*
  • Microbiota*
  • Middle Aged
  • Phylogeny
  • Public Health Surveillance / methods
  • Young Adult


  • DNA, Bacterial
  • DNA, Ribosomal