Viability of human milk microbiota

Numerous studies have characterised the human milk microbiome using DNA sequencing technologies, particularly 16S rRNA gene sequencing. However, such methods are not able to differentiate between DNA from viable and non-viable bacteria. It is therefore unclear the extent to which bacterial DNA detected in human milk represents living, biologically active cells. Here, we characterised both the viable bacterial content of fresh human milk (n=10), and the total bacterial DNA content (derived from viable and non-viable cells). In order to differentiate the living from the dead, a combination of propidium monoazide and full-length 16S rRNA gene sequencing was used.