What is the cause of urinary tract infection?

Urinary tract infection refers to the infection caused by pathogenic microorganisms invading the urinary tract. Most of the pathogenic bacteria are Escherichia coli. The infection route is upward or direct infection. It can be divided into upper urinary tract infection, mainly pyelonephritis, lower urinary tract infection, mainly cystitis. The main symptoms of urinary system are urinary pain, urgency, frequent urination, pubic discomfort or falling feeling. Urine routine examination visible pus cells or leukocytes cast, urine bacteria culture in the middle positive.