page_title: Urinary tract infection
section_title: Cause
hierarchical_section_title: Urinary tract infection / Cause
caption_attribution_description: English: Uropathogenic Escherichia coli (UPEC) cells adhered to bladder epithelial cell (BEC). Cells stained with methylene blue and fuchsine.
context_page_description: A urinary tract infection is an infection that affects part of the urinary tract. When it affects the lower urinary tract it is known as a bladder infection and when it affects the upper urinary tract it is known as a kidney infection. Symptoms from a lower urinary tract infection include pain with urination, frequent urination, and feeling the need to urinate despite having an empty bladder. Symptoms of a kidney infection include fever and flank pain usually in addition to the symptoms of a lower UTI. Rarely the urine may appear bloody. In the very old and the very young, symptoms may be vague or non-specific.
  The most common cause of infection is Escherichia coli, though other bacteria or fungi may sometimes be the cause. Risk factors include female anatomy, sexual intercourse, diabetes, obesity, and family history. Although sexual intercourse is a risk factor, UTIs are not classified as sexually transmitted infections. Kidney infection, if it occurs, usually follows a bladder infection but may also result from a blood-borne infection. Diagnosis in young healthy women can be based on symptoms alone.
context_section_description: Uropathogenic E. coli from the gut is the cause of 80–85% of community-acquired urinary tract infections, with Staphylococcus saprophyticus being the cause in 5–10%. Rarely they may be due to viral or fungal infections. Healthcare-associated urinary tract infections (mostly related to urinary catheterization) involve a much broader range of pathogens including: E. coli (27%), Klebsiella (11%), Pseudomonas (11%), the fungal pathogen Candida albicans (9%), and Enterococcus (7%) among others. Urinary tract infections due to Staphylococcus aureus typically occur secondary to blood-borne infections. Chlamydia trachomatis and Mycoplasma genitalium can infect the urethra but not the bladder. These infections are usually classified as a urethritis rather than urinary tract infection.
caption: Uropathogenic Escherichia coli (UPEC) cells adhered to bladder epithelial cell.
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