Introduction For treatment of Mycoplasma genitalium (Mg) infection, azithromycin is first line initial treatment but persistent NGU caused by Mg may not respond to repeat azithromycin treatment; quinolones, in particular moxifloxcin, have been shown to be effective. The molecular epidemiology of mutations in macrolide- and quinolone-resistance determining regions (RDRs) of 23S rRNA, parC and gyrA genes remains unclear in China.

Methods From April 2011 to August 2015, male subjects with clinical and microscopic evidence of urethritis provided a first-voided urine specimen and the mgpA gene was partially amplified and sequenced to diagnose Mg infection. RDRs of the 23s rRNA, parC and gyrA genes were sequenced.

Results Among 1816 male-patients, the overall prevalence of M. genitalium was 19.7% (358/1816). N. gonorrhoeae prevalence was 46.6% (847/1816). Among 969 NGU-cases, prevalence of: C. trachomatis was 42.3% (409/968), M. genitalium 27.9% (271/969), U. urealyticum 21.3% (182/856), T. vaginalis1.8% (17/969) and M. hominis 0.7% (6/855). Based on data available from partial (5.4%) sequencing of the MgPa gene (mgpA) an evolutionary tree was constructed that divided the 358 Mg mgpA sequences into five major clusters. Among 358 Mg positive samples, successful sequencing was accomplished for: the 23s rRNA gene (341 specimens), the parC gene (344 specimens) and the gyrA gene (339 specimens). 88.9% (303/341) had mutations in 23s rRNA, 89.5% (308/344) had sense mutations in parC, and 12.4% (42/339) had sense mutations in gyrA.The most common single base pair mutation in the 23s rRNA gene was A2059G (211/303; 69.6%) followed by A2058G (60/303; 19.8%) and A2059T (30/303; 9.9%). The most common mutation in the parC gene was G248T (289/344; 84%) and in the gyrA gene G285A (22/339, 6.5%).

Conclusion The high mutation rate in 23s rRNA and parC in Mg strains in Nanjing are a harbinger of resistance to macrolides and quinolones that may follow. Molecular surveillance of indigenous strains of Mg is warranted to anticipate the development of antimicrobial resistance.