Isolation of active Pseudomonas aeruginosa bacteriophages and of their host from human breast milk

Human breast milk (HBM) contains diverse bacterial and viral communities that impact early-life microbiome development. Metagenomic studies reported the presence of bacteriophage DNA in HBM samples, but not yet of bacteriophage particles. Here, six Pseudomonas aeruginosa –infecting bacteriophages and a co-occurring P. aeruginosa strain were isolated directly from HBM of a lactating woman. Genomic characterization revealed four lytic phages (among which three showing highly similar host ranges and comparable plaque morphologies) and two temperate phages, spanning multiple genera. Host-range profiling indicated a broad activity, including against the co-occurring P. aeruginosa strain. Synergistic interactions were observed between lytic phages or between lytic phages and one temperate phage. These findings elicit questions towards phage–host dynamics in HBM and highlight implications towards neonatal microbial colonization and immune modulation.