Urinary tract infections (UTIs) are caused primarily by bacteria entering the urinary tract through the urethra and infecting the bladder, and sometimes the kidneys. The most common bacteria responsible for UTIs is Escherichia coli (E. coli), which normally live in the bowel and around the anus. Other bacteria like Staphylococcus saprophyticus and, in rare cases, bacteria from the bloodstream such as Salmonella or Staphylococcus aureus can also cause UTIs. Several factors increase the likelihood of bacteria entering and infecting the urinary tract:
- Female anatomy: Women have a shorter urethra and its proximity to the anus makes it easier for bacteria to reach the bladder.
- Sexual activity: In young women, frequent sexual activity is a common cause of bladder infections.
- Certain birth control methods: Using spermicide or a diaphragm may increase risk.
- Problems with bladder emptying: Conditions like an enlarged prostate in men or urinary incontinence can cause urine to remain in the bladder longer, allowing bacteria to multiply.
- Urinary catheters: Use of catheters can introduce bacteria.
- Other risk factors: Pregnancy, obesity, a personal or family history of UTIs, kidney stones, chronic health problems like diabetes, weakened immune system, and being uncircumcised in infant boys.
Bacteria typically come from the bowel and are transmitted to the urinary tract through routes such as sexual intercourse or improper hygiene (e.g., wiping back to front after bowel movements). Once in the bladder, bacteria like E. coli attach to the bladder wall and can form protective biofilms, resisting the immune response and causing infection. UTIs can infect different parts of the urinary tract including the urethra, bladder, ureters, and kidneys. Treatment usually involves antibiotics to eliminate the bacteria causing the infection. Prevention focuses on hygiene, staying hydrated, and managing risk factors. In summary, UTIs are caused by bacterial invasion of the urinary tract, most commonly E. coli from the bowel, facilitated by anatomical, behavioral, and medical factors that allow bacterial colonization and infection of the bladder or kidneys.
