Classification of non-gonococcal urethritis: a review

Non-gonococcal urethritis (NGU) is the most common disease of the genital tract in men. Recent studies have recommended avoiding the empiric antibiotic administrations that constitute the classical treatment approach in NGU and to aim toward treatment of causative pathogens. However, the classification of NGU agents remains controversial. In addition, the relevance of the commensalism of Mycoplasma hominis, Ureaplasma urealyticum, Ureaplasma parvum, and Gardnerella vaginalis, which are among the opportunistic pathogens found in the urethral flora, has yet to be determined. Furthermore, there are certain pathogens on which sufficient studies have not been conducted, although they are known to be NGU pathogens, and their statuses should be updated. In this review, the classification of NGU pathogens is summarized in the light of the current literature.