Which bacteria can colonize the urinary tract?

E. coli...: Urinary tract infections typically occur when bacteria enter the urinary tract through the urethra and begin to multiply in the bladder. The most common utis occur mainly in women and affect the bladder and urethra. Infection of the bladder (cystitis) can be caused by e. Coli, a type of bacteria commonly found in the gastrointestinal tract but can also be caused by many other types of bacteria.