• antimicrobial susceptibility;
  • infection;
  • Mycoplasma genitalium;
  • treatment;
  • urethritis


Male urethritis is a common disease for urologists, with the most common pathogens being, Chlamydia trachomatis and Neisseria gonorrhoeae. When the tests fail to detect these pathogens, the presented urethritis is called non-chlamydial non-gonococcal urethritis. Mycoplasma genitalium is one of the pathogens for non-chlamydial non-gonococcal urethritis. The test for detecting M. genitalium, which is commercially available in Japan, is not accepted by the Japanese insurance system now. The detection rate of M. genitalium from patients with non-gonococcal urethritis is 10–20% in Japan. Antimicrobial susceptibility testing for M. genitalium showed that macrolide has the strongest activity and the minimum inhibitory concentrations of tetracyclines were not substantially lower. Some kinds of fluoroquinolones, such as sitafloxacin and moxifloxacin, have stronger activities against M. genitalium. For non-gonococcal urethritis, macrolides and tetracycline are recommended in some guidelines. In clinical studies, tetracyclines are less effective against M. genitalium than azithromycin, and azithromycin regimens including 1 g stat or 2 g stat are now recommended for urethritis with M. genitalium. However, macrolide-resistant M. genitalium strains have recently emerged and are spreading worldwide. This macrolide-resistance is closely related to mutations on the 23S rRNA gene. Sitafloxacin and moxifloxacin have shown good efficacies for M. genitalium in some clinical studies. If the azithromycin regimens fail, we must consider the use of fluoroquinolones, such as sitafloxacin, in Japan. The most important issues include the acceptance of M. genitalium examinations by the national insurance system and the individual treatment of C. trachomatis and M. genitalium in the not-too-distant future.