The healthy bladder is not sterile

Researchers at Loyola University Chicago collected bladder urine from 23 surgical patients, 12 without urinary symptoms, by catheter and by needle through the abdomen, then tested it for bacteria that routine lab cultures are not built to detect.

Alan Wolfe's team found bacteria, frequently Lactobacillus species, in urine from women who had no urinary symptoms at all. Standard clinical cultures, the kind ordered for a suspected infection, are built to grow a narrow set of known pathogens and routinely miss these other bacteria, which is why the bladder had been called sterile.

The finding helped launch sustained research into a urinary microbiome, now studied for its possible role in incontinence and recurrent infections. The original sample was small and limited to women, and later work using broader sequencing methods has kept expanding the list of bacteria that live in the bladder without causing any disease.

Sterile was the wrong word all along.