American Scientist

For decades, medical students have typically been—and still are—taught that the bladder is sterile, but research over the past 15 years has confirmed what some of us have long suspected: The bladder has a microbiome, a resident community of microbes. This simple fact has profound implications for the most common infection treated in clinics around the world: the urinary tract infection (UTI). More than 400 million people globally are diagnosed with UTIs every year, making up 25 percent of all infections treated. UTIs are most common in people assigned female sex at birth, especially as they get older.