Macrolide and fluoroquinolone resistance is uncommon in clinical strains of Chlamydia trachomatis.

Abstract

We analyzed the 23S rRNA, gyrA and parC genes of Chlamydia trachomatis DNAs from men with urethritis and determined microbiological outcomes of an extended-release azithromycin (azithromycin-SR) regimen (2g once daily for 1 day) and a sitafloxacin regimen (100mg twice daily for 7 days) for chlamydial urethritis to clarify the macrolide and fluoroquinolone resistance status of clinical strains of C.trachomatis. We amplified the portions of 2 alleles of the 23S rRNA gene and the gyrA and parC genes from C.trachomatis DNAs in 284 first-voided urine specimens from men with chlamydial urethritis by PCR and sequenced their PCR products. We enrolled 369 men with chlamydial urethritis, comprising 314 and 55 treated with the azithromycin-SR regimen and the sitafloxacin regimen, respectively. Alleles 1 and/or 2 of the 23S rRNA gene were analyzed in 162 specimens. No mutations were found in the sequenced regions, including the central portion of domain V. The gyrA and parC genes were analyzed in 118 and 113 specimens, respectively. No amino acid changes were found within the quinolone resistance-determining region of the gyrA gene and in the sequenced region of the parC gene. The microbiological outcomes of the azithromycin-SR and sitafloxacin regimens were assessed in 176 and 30 men, respectively. The eradication rates were 96.0% (95% CI 93.1%-98.9%) for the azithromycin-SR regimen and 100% for the sitafloxacin regimen. Clinical strains of C.trachomatis with macrolide and/or fluoroquinolone resistance would be uncommon, and azithromycin or fluoroquinolone regimens could be recommended as treatments for chlamydial infections.