What is the primary causative agent of nongonococcal urethritis in men?

The primary causative agent of nongonococcal urethritis (NGU) in men is Chlamydia trachomatis. This organism is commonly responsible for a significant proportion of cases of urethritis that are not caused by gonorrhea. Chlamydia infections are often asymptomatic, which means that men may be infected without displaying any noticeable symptoms, but the infection can still cause inflammation of the urethra.

In addition to being the most prevalent cause of NGU, Chlamydia can lead to other complications if left untreated, such as epididymitis and potential infertility. The diagnosis of NGU often involves testing for Chlamydia, especially when gonococcal infections have been ruled out.

While Escherichia coli can occasionally contribute to urethritis, it is not the primary causative agent for NGU in men. Gonorrhea, on the other hand, is specifically associated with gonococcal urethritis, and Mycoplasma species, while also implicated in some cases, are less common causes compared to Chlamydia. Thus, Chlamydia remains the leading pathogen associated with nongonococcal urethritis in the male population.