Clinical Microbiology and Antimicrobial Chemotherapy. 2004; 6(1):54-64
Susceptibility of 25 clinical isolates of Chlamydia trachomatis to the most commonly used antimicrobials for the treatment of chlamydial infections was studied. Of 25 isolates, 10 were determined as in vitro resistant to doxycycline, 10 – to azithromycin, 11 – to josamycin, 11 – spiramycin, and 11 – to ofloxacin. Multiple drug resistance was observed in 12 isolates; 6 of them were resistant to all tested antimicrobials. Chlamydia tested were found to express heterotypic resistance – only a small proportion of cells (<1%) demonstrated survival after exposure to high levels of antimicrobials. A comparison of the results of follow-up microbiological tests with the in vitro antimicrobial susceptibility of the isolated strains of C. trachomatis was made. No correlation between clinical efficacy and heterotypic resistance of isolated strains was found. Of 25 included patients, 9 received antimicrobials, to which chlamydia isolated before treatment were in vitro resistant, but no chlamydia were isolated from these patients after treatment. Conversely, the only strain that was isolated from the patient after treatment was susceptible to antichlamydial agent used. Therefore, antimicrobial susceptibility testing of chlamydia is an unreasonable method to guide the choice of appropriate agents for the treatment of chlamydial infection.