title: Differences in 23S ribosomal RNA mutations between wild-type and mutant macrolide-resistantChlamydia trachomatisisolates.
abstract: The aim of the present study was to determine thein vitrosusceptibility of wild-type and mutant clinical isolates ofChlamydia (C.) trachomatisstrains to erythromycin, azithromycin and josamycin, and to identify the resistance-conferring 23S ribosomal (r)RNA mutations in the isolates. The wild-type resistant isolates were defined as those with minimum inhibitory concentration values above the tissue concentration of the antibiotic in the urogenital system. Furthermore, all resistantC. trachomatisisolates were exposed to sub-inhibitory concentrations of macrolides, and 13 resistant mutants were selected following serial passages. Among the 8 wild-type isolates that were resistant to erythromycin, 3 isolates had a mutation at T2611C in the 23S rRNA gene while the others did not show any 23S rRNA mutations. The selected mutant isolates showed a 4- to 16-fold reduction inin vitrosensitivities. With regard to the mutant strains, the T2611C mutation was found in 10 isolates, A2057G mutation in 6 isolates, and A2059G mutation in 1 isolate. Thus, the macrolide-resistant isolates of the wild-type strain had different mutations from those selected by exposure to sub-inhibitory concentrations of macrolides. Also, since 23S rRNA mutations were not identified in certain isolates, it was considered that other molecular mechanisms may also be responsible for the macrolide resistance ofC. trachomatis.
authors.affiliation: Department of Dermatology, The Second Hospital of Tianjin Medical University, Heping, Tianjin 300052, P.R. China.
authors.forename: Yong
authors.initials: Y
authors.lastname: Jiang
authors.affiliation: Department of Dermatology, The Second Hospital of Tianjin Medical University, Heping, Tianjin 300052, P.R. China.
authors.forename: Hui
authors.initials: H
authors.lastname: Zhu
authors.affiliation: Department of Dermatology, The Second Hospital of Tianjin Medical University, Heping, Tianjin 300052, P.R. China.
authors.forename: Li-Na
authors.initials: LN
authors.lastname: Yang
authors.affiliation: Department of Dermatology, General Hospital of Tianjin Medical University, Heping, Tianjin 300052, P.R. China.
authors.forename: Yuan-Jun
authors.initials: YJ
authors.lastname: Liu
authors.affiliation: Department of Dermatology, General Hospital of Tianjin Medical University, Heping, Tianjin 300052, P.R. China.
authors.forename: Shu-Ping
authors.initials: SP
authors.lastname: Hou
authors.affiliation: Department of Dermatology, General Hospital of Tianjin Medical University, Heping, Tianjin 300052, P.R. China.
authors.forename: Man-Li
authors.initials: ML
authors.lastname: Qi
authors.affiliation: Department of Dermatology, General Hospital of Tianjin Medical University, Heping, Tianjin 300052, P.R. China.
authors.forename: Quan-Zhong
authors.initials: QZ
authors.lastname: Liu
keywords: 23S rRNA; Chlamydia trachomatis; macrolide; point mutation