Recurrent urinary tract infections are a widespread problem, particularly in women.Most episodes are caused by uropathogenic Escherichia coli. Reservoirs of these bacteria may not only reside at distant anatomical sites such as the intestinal tract, rectum, perineum and vagina, but also intracellularly within the bladder epithelia. Antimicrobial therapies used to treat primary urinary tract infections or prevent recurrences disrupt other bacteria in the distal urethra and vagina, and negate their ability to fend off the pathogens and prevent infection.