Abstract: CHEN Li-xin *, WANG Rui, YOU Cong, LIU Zhi-chao, WANG Jing, LI Zhuo-ran, LIU Yuan-jun, LIU Quan-zhong. *Department of Dermatology, General Hospital, Tianjin Medical University, Tianjin 300052, China Corresponding author: LIU Quan-zhong, Email: liuquanzhong@medmail.com.cn 【Abstract】 Objective To investigate the effect of orally administered antimicrobial agents on the cultivation and antimicrobial susceptibility of urogenital Chlamydia trachomatis （CT）. Methods Totally, 285 patients with urogenital CT infection diagnosed by direct immunofluorescence from 2010 to 2012 were recruited in this study. Of them, 61 patients were untreated, and 224 had received a course of regular antimicrobial treatment 5 weeks before the recruitment. Urethral or cervical swab specimens were collected from all of these patients and subjected to CT culture. The relationship of antimicrobial treatment with the culture-positive rate and the minimum number of passages required for the detection of CT inclusion bodies was assessed. In vitro susceptibility test was performed on the clinical CT isolates. Results Of the 285 clinical specimens, 39 were positive for CT by cell culture. The CT culture-positive rate was 27.87% （17/61） in untreated patients and 9.82% （22/224） in treated patients （χ2 = 13.22, P < 0.05）. Of the 17 positive specimens from untreated patients, 4 were identified as positive after 1 passage of culture, 5 after 2 passages, 5 after 3 passages, 2 after 4 passages, and 1 after 5 passages. Meanwhile, among the 22 positive specimens from treated patients, 2 were identified as positive after 2 passages, 3 after 3 passages, 9 after 4 passages, 6 after 5 passages, 2 after 6 passages. Rank sum test showed that the minimum number of passages required for the detection of CT inclusion bodies was statistically lower in the specimens from untreated patients than those from treated patients （P < 0.05）. The CT isolates from untreated patients showed a reduced antimicrobial sensitivity compared with those from treated patients. Conclusions Compared with the specimens taken from untreated patients, those from treated patients exhibit a lower CT culture-positive rate but an increased minimum number of passages required for the detection of CT inclusion bodies. 【Key words】 Chlamydia trachomatis ; Treatment outcomes; Culture techniques; Microbial sensitivity tests