<Tr> <Th> Specialty </Th> <Td> Urology </Td> </Tr> <P> Nongonococcal urethritis (NGU) is an inflammation of the urethra that is not caused by gonorrheal infection . </P> <P> For treatment purposes, doctors usually classify infectious urethritis in two categories: gonococcal urethritis, caused by gonorrhea, and nongonococcal urethritis (NGU). </P> <P> The symptoms of urethritis can include pain or a burning sensation upon urination (dysuria), a white / cloudy discharge and a feeling that one needs to pass urine frequently . For men, the signs and symptoms are discharge from the penis, burning or pain when urinating, itching, irritation, or tenderness . In women, the signs and symptoms are discharge from vagina, burning or pain when urinating, anal or oral infections, abdominal pain, or abnormal vaginal bleeding, which may be an indication that the infection has progressed to Pelvic Inflammatory Disease . </P>

Which of the following is the most common cause of ngu (nongonococcal urethritis)