Antimicrobial Susceptibility And Resistant Mechanism Of Chlamydia Trachomatis Clinical Isolates

OBJECTIVE To investigate the antimicrobial susceptibility in vitro and study on resistant mechanism of clinical isolates of Chlamydia trachomatis.METHOD 237 patients were diagnosed with genital infections with Chlamydia trachomatis.After culture in McCoy cells,clinical strains took the susceptibility test of 10 kinds of antimicrobials(erythromycin,clarithromycin,azithromycin,tetracycline,doxycycline,minocycline,levofloxacin,moxifloxacin,sparfloxacin,rifampin).Amplified the 23S rRNA,tetM,gyrA and rpoB genes.The PCR product were subsequently sequenced or analyzed with restriction fragment length polymorphism,single-strand conformation polymorphism.Additionally gene type were studied.RESULT 82 strains were cultured successfully.52 strains of them had the susceptibility test.13 erythromycin-resistant strains were isolated.23S rRNA of 8 resistant strains were sequenced and all had the mutations A2131T,3 of them had the mutations T2611C.59 of 69 strains had tetM gene.After Tsp509 I digestion,Ser83→Ile mutations were not found in gyrA gene of 71 strains.After single-strand conformation polymorphism analysis,no mutations were found in rpoB gene of 58 strains.53 clinical isolates were Type E,2 isolates were Type G,1 isolate was Type J.CONCLUSION The antimicrobials are getting less effective than before.25% clinical strains are resistant to erythromycin.Some of them have the mutation T2611C,the new mutations A2131T(not reported)maybe are related to resistance. The induced resistant mutations of gyrA and rpoB gene are not common in clinical strains.Other mechanisms involving drug permeation and drug efflux modifications may contribute to the clinical resistance to various antimicrobials in clinical strains. The antimicrobials susceptibility test in vitro are need to be improved or replaced with molecular biological method.Type E is still the main gene type.