When does staph saprophyticus infection occur?

The Staph saprophyticus can cause a local spread on the outside and move to the UT to cause cystitis , acute cystitis is the inflammation of the bladder usually it happens in sexually active young females but it is not an STI it is just a UTI , when we talk about STI this means that the organism is mainly if not absolutely transmitted through sex like gonorrhea and chlamydia and heaemophilus ducreyi . Staph it is just a simple UTI