the bacteria that cause urinary tract infections usually go into the bladder from the uretha. it is believed these bacteria come from the bowel. females are at greater risk because they have a short urethra that is close to their anus). after entering the bladder, "e. coli" are able to stick to the bladder wall. they form a biofilm, which is a coating of microorganisms, that resists the body's immune response. however, infections can also come through the blood or lymph.