Background Mycoplasma genitalium is one of the pathogens of male urethritis. Macrolides as azithromycin can be the first line-treatment, but macrolides-resistant M genitalium strains were isolated. We tried to use some fluoroquinolones against M genitalium-related urethritis. In these studies, some patients could not treated by fluoroquinolone. In any bacteria, genetic mutations on gyrase genes were related to fluoroquinolone-resistance. In this study, quinolone-resistant determining regions (QRDR) on gyrase genes of M genitalium were analysed and the relationship between the efficacies of fluoroquinolone against M genitalium-related urethritis and genetic mutations on QRDR of M genitalium was examined.

Methods The QRDR on gyrA and parC genes of M genitalium were sequenced and analysed. DNA samples were purified from M genitalium-positive first-voided urine specimens before and after the treatment with fluoroquinolones as gatifloxacin or sitafloxacin. The QRDR of gyrA and parC genes of M genitalium were analysed by using primers according to Shimada's report (Int J Antimicrob Agent, 2010).

Results Twenty-two genomes of M genitalium before the treatment with fluoroquinolones and four genomes from patients with treatment-failure were analysed. Before the treatment, M genitalium genomes have no mutation on gyrA, but had four mutations on parC gene with amino-changes (Ala-69 to Thr, Pro-72 to Ser, Asp-87 to His and Ser-83 to Ile). After the treatment, M genitalium was found in four patients and all remained M genitalium were found mutations on gyrA or parC with amino-changes. M genitalium with mutation on parC (Pro-72 to Ser and Ser-83 to Ile) before treatment was remained. M genitalium with mutation on parC (Pro-72 to Se and Ser-83 to Ile) before treatment was remained and was found additional gyrA mutation (Asp-99 to Asn). In two patients, M genitalium without mutations before treatment remained after treatment. However, these genomes were found with newer mutations on gyrA (Asp-99 to Asn) or on parC (Ser-83 to Ile).

Conclusion From the urine specimens of patients with treatment-failure of fluoroquinolones, some mutations with amino-change were found on QRDR of gyrA or parC genes of M genitalium. It was suggested that these mutations are related with treatment-failure with fluoroquinolones.