Recent research published in 2018 has shown that bacteriophages are more abundant than bacteria themselves in the human bladder.

Loyola University, Chicago, and Loyola University Medical Center analysed the sequencing data from bacteria collected from the bladders of 181 female patients with and without urinary problems. The researchers identified more than 450 possible phage sequences within the majority of the nearly 200 bacterial genomes that they examined. More than half of these viral sequences were not found in any databases, suggesting that they could be phages unique to the urinary tract.

The authors found sequence similarities in phages from different women, which points to the possibility of a shared set of bladder phages. They also saw some variations in phage populations between the samples from women with and without urinary issues, including overactive bladder, incontinence, bladder pain, and urinary tract infection.

To determine whether the phage sequences they detected were intact and able to infect bacteria, the team isolated a new phage from an E. coli strain in the bladder. They captured electron micrographs of the purified phage and tested whether it could lyse bacteria in culture. Although the virus was originally integrated into the host’s genome, it was able to kill other bacteria, suggesting that it is indeed a functional bacteriophage.

They concluded “Our survey of lysogenic phages provides the first step in the process of unraveling the complex dynamics of phage-bacterium interactions within the urinary microbiota. Additional sequencing of the bacterial population within the bladder, coupled with further metagenomic sequencing of the urinary virome, is needed to both determine if a core “bladder phageome” exists and whether phages play a role in urinary health and disease.