In vitro susceptibility to 6 antimicrobial agents and genotyping of clinical isolates of Chlamydia trachomatis.

Abstract

Objective To assess the vitro susceptibility to 6 antimicrobial agents and genotypes ofclinical isolates of Chlamydia trachomatis (Ct) from Guangzhou region. Methods Ct was isolated from clinicalspecimens by using McCoy cell culture and subjected to propagation. The minimum inhibitory concentration(MIC) and minimal bactericidal concentration (MBC) of 6 antimicrobial agents (clarithromycin, roxithromycin,azithromycin, doxycycline, tetracycline, ofloxacin) against Ct isolates were determined in McCoy cell culture.Nested PCR was performed to amplify the outer membrane protein 1 (omp1) VS1-2 gene followed by sequencing.Results Seventy-six Ct strains were isolated from 346 urogenital specimens, and 40 strains met the requirements for susceptibility testing after serial propagation. The MIC50/MIC90 of clarithromycin, azithromycin, roxithromycin, doxycycline, tetracycline and ofloxacin were as follows: 0.008/0.032, 0.080/0.160, 0.125/0.500,0.032/0.064, 0.250/0.500 and 0.500/1.000 mg/L. Seven genotypes were observed. The most prevalent genotypes in decreasing order were E (14, 35%), J (10, 25%)and F (6, 15%). The MIC50 was consistent forazithromycin among the 7 genotypes, but varied by 1 - 4 folds for doxycycline, ofloxacin and roxithromycin.Conclusions Clarithromycin, doxycycline and azithromycin exhibit an excellent activity against Ct, and theactivity of azithromycin is consistent among the 7 genotypes of Ct. Key words: Chlamydia trachomatis; Genotype; Microbial sensitivity tests