The bladder is not sterile: History and current discoveries on the urinary microbiome

In the human body, there are 10 bacterial cells for every one human cell. This fact highlights the importance of the National Institutes of Health’s initiative to map the human microbiome. The Human Microbiome Project was the first large-scale mapping of the human microbiome of five body sites: GI tract, mouth, vagina, skin, and nasal cavity using culture-independent methods. The bladder was not originally tested because it was considered to be sterile and there were complexities regarding sample collection. Over the last couple years, our team along with other investigators has shown that a urinary microbiome exists and for most individuals, it plays a protective role.