We developed a TaqMan-based real-time PCR assay for quantifying Mycoplasma genitalium. This assay is able to specifically quantify concentrations of the M. genitalium 16S rRNA gene ranging from 10 7 to 10 copies/reaction. Using the TaqMan assay, we quantified the M. genitalium 16S rRNA gene in first-pass urine of men with urethritis and asymptomatic men who were positive for M. genitalium by PCR-and phylogenybased assay. Of 130 men with gonococcal urethritis (GU), five were positive for M. genitalium. The mycoplasma load for each specimen was <5 ؋ 10 copies/ml. Of 84 men with chlamydial non-GU (CNGU), seven were positive for M. genitalium. One man had an M. genitalium load of <5 ؋ 10 copies/ml, and six men had loads ranging from 1.1 ؋ 10 7 to 2.7 ؋ 10 2 copies/ml. Of 86 men with nonchlamydial NGU (NCNGU), 17 were positive for M. genitalium. The mycoplasma loads for these men ranged from 3.3 ؋ 10 6 to 2.3 ؋ 10 2 copies/ml. Of 76 asymptomatic men, only two were positive for M. genitalium. For these men, the loads were 2 ؋ 10 2 and <5 ؋ 10 copies/ml. The patients with NGU had significantly higher concentrations of M. genitalium in their first-pass urine than did men with GU (P < 0.01) or asymptomatic men (P < 0.05). In addition, M. genitalium loads were significantly higher in men with NCNGU than those in asymptomatic men (P < 0.05). The quantitative assessment of M. genitalium loads by the TaqMan assay will provide useful information for understanding the pathogenicity of this mycoplasma in the urogenital tract.Mycoplasma genitalium was isolated in urethral cultures from two men with nongonococcal urethritis (NGU) in 1981 (21). Although M. genitalium had been proposed as a cause of human NGU (22), the precise role of the mycoplasma in the etiology of NGU had not been established because of the immense difficulty in isolating it from clinical samples. Since PCR-based assays facilitated the detection of M. genitalium in clinical specimens (10, 17), a significant association between M. genitalium and NGU has been demonstrated (7,9,13,20). So far, however, any studies to investigate the potential association of M. genitalium loads with the pathogenicity of the mycoplasma in the urogenital tract have not been performed, because isolation of M. genitalium in culture is still difficult and because conventional PCR-based assays are lacking in quantitative assessment of the mycoplasma in clinical specimens. For this study, therefore, we developed a TaqMan-based real-time PCR assay for quantifying M. genitalium. Using this assay, we quantified M. genitalium DNA in first-pass urine of men with urethritis and asymptomatic men and assessed whether the bacterial load of M. genitalium might be associated with the pathogenicity of the mycoplasma in the urogenital tract.
MATERIALS AND METHODS
Bacterial strains. Strains of 15 species of human mycoplasmas and ureaplasmas, including Mycoplasma buccale, Mycoplasma faucium, Mycoplasma fermentans, M. genitalium, Mycoplasma hominis, Mycoplasma lipophilum, Mycoplasmaorale, Mycoplasma pene...