High-resolution multilocus sequence typing of urogenital Chlamydia trachomatis among STD clinic outpatients in Guangxi Zhuang Autonomous Region

Abstract

Objective To investigate the type distribution of urogenital Chlamydia trachomatis (Ct) among STD clinic outpatients in Guangxi Zhuang Autonomous Region, and to estimate the prevalence of Ct infection among the patients during posttreatment follow-up. Methods Urethral and cervical swabs were collected from male and female outpatients with confirmed urogenital Ct infection, respectively, in Institute of Dermatology of Guangxi Zhuang Autonomous Region. The patients with positive results in preliminary screening tests were followed up after treatment, and specimens were collected at follow-up visits. General and clinical information was also obtained from these patients. DNA was extracted from these samples by using the QIAxtractor instrument. Nested PCR was performed to amplify the major outer membrane protein A (ompA) gene for ompA typing, and to amplify CT046 (hctB), CT058, CT144, CT172 and CT682 (pbpB) genes for high-resolution multilocus sequence typing (hr-MLST). Then, PCR products were sequenced, and ompA and MLST types of Ct were determined by sequence alignment and MLST analysis, respectively. The obtained MLST sequence types (STs) were compared with those from an Italian population by using the BioNumerics7 software, and a minimum spanning tree (MST) was generated. Results Totally, 44 and 6 Ct-positive specimens were collected at first visits and follow-up visits respectively. Among the 50 specimens, 42 underwent successful ompA typing and hr-MLST, and 7 ompA genotypes and 15 hr-MLST STs were identified, including 3 first reported STs. The distribution of STs of Ct isolates from Guangxi Zhuang Autonomous Region was significantly different from that from the Italian population. Among the 6 followed patients with posttreatment Ct infection, 3 were confirmed to be reinfected with Ct, and the other 3 failed to be diagnosed because of unsuccessful genotyping. Conclusion The genotypes of Ct strains isolated from STD clinic outpatients in Guangxi Autonomous Region were characteristic, and Ct reinfection occurred in some patients during follow-up. Key words: Chlamydia trachomatis; Multilocus sequence typing; Follow-up studies; Cluster analysis