In Vitro Susceptibility Of Various Antibiotics Alone And In Combination With Other Antibiotics Against Chlamydia Trachomatis

Chlamydia trachomatis is the most common pathogen of venereal disease internal and abroad. It also causes many complications and serious mental stress to the patients. In our country, the incidence of Ct infection is also found an increasing trend year by year, which becomes a pernicious public health problem.Currently, urogenital Ct infection incidence is closely related to its prevalence, so antibiotic therapy is an important strategy for secondary prevention of disease; the same time as Ct vaccine is still not available for clinical, so antibiotics for the treatment of Ct infection has become more important. However, Ct infection in patients with clinical manifestations are often nonspecific or concealed and difficult to pay attention, resulting in persistent disease, relapse or recurrent infection. Ct causes a variety of reduced susceptibility to antimicrobial agents and clinical treatment failure cases increase dramatically.Objective:To test the in vitro individual and combined activity of azithromycin,minocyline,moxifloxacin,doxycycline and rifampicin against urogenital standard strains and the clinic isolates of Ct. Moreover to explore diversity of the susceptibility of Ct and the relation between the clinic curative effects and the experimental results. To reserve the Ct positive clinical strains and it will lay a foundation for further research.Methods:Collecting urethral or cervix swabs from the patients who came to Tianjin Institute of sexually transmitted diseases from September 2005 through to June 2009. We undertook cell culture of clinical samples with McCoy cell on the foundation of Ct E standard strain. All the clinical strains had been blind-passage cultured. The positive strains of the fifth generation were kept on culturing. All the forty-one clinical isolates from patients were typed by detection of restriction fragment length polymorphism in the gene encoding the major outer membrance protein of Ct. Determination of the MICs and FICs was performed by inoculating Ct strains onto monolayers of the McCoy cell line. Finding clinical treatment failure isolates and studying them for possible mutations in 23S rRNA by RT-PCR. To test the most frequent mutations of gyrA QRDR associated with quinolone resistance by RFLP.Results:41 positive samples were detected by the culture technique in 238 cases and the positive rate was 17.23%. MIC of the 41 Ct clinical ranges were as follows (ug/ml):azithromycin 0.063～0.5, moxifloxacin 0.03～0.24, minocycline 0.008～0.064, doxycycline 0.063-0.5, rifampin 0.002～0.016。FICs were as follows: synergism and additivity effects were observed when azithromycin was combined with moxifloxacin, doxycycline and rifampin; neverless, antagonism effects were observed when minocyline was combined with azithromycin, moxifloxacin and rifampin. And we did not find resistance genes of clinical treatment failure isolates.Conclusions:1. Successful Ct culture establishes good foundation for further laboratory research of Ct including pathogenesis, immunologic mechanism, drug susceptibility test, resistance mechanism, and protective vaccine so on.2. Antibiotic sensitivity showed different degreees of declining. We found that there was difference between the clinic curative effect and the experiment result.3. We can assume some antimicrobials combinations may possibly represent a new treatment strategy.