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Symptoms and Causes
Escherichia coli (E. coli) causes about 80% of UTIs in adults. These bacteria are normally present in the colon and may enter the urethral opening from the skin around the anus and genitals. Other bacteria that cause urinary tract infections include Staphylococcus saprophyticus (5 to 15% of cases), Chlamydia trachomatis, and Mycoplasma hominis. Men and women infected with chlamydia trachomatis or mycoplasma hominis can transmit the bacteria to their partner during sexual intercourse, causing UTI.
Urinary catheterization (small tube inserted into the bladder through the urethra to drain urine) can also cause UTI by introducing bacteria into the urinary tract. The risk for developing a UTI increases when long-term catheterization is required.
In infants, bacteria from soiled diapers can enter the urethra and cause UTI. E. coli may also enter the urethral opening when young girls do not wipe from front to back after a bowel movement.
Other risk factors include the following:
• Bladder outlet obstructions (e.g., kidney stones, BPH);
• Conditions that cause incomplete bladder emptying (e.g., spinal cord injury);
• Congenital (present at birth) abnormalities of the urinary tract (e.g., vasicoureteral reflux);
• Suppressed immune system;
• Being uncircumcised.
Certain blood types enable bacteria to attach more easily to cells that line the urinary tract, causing recurrent UTIs.
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