Comparative in vitro susceptibility of a tetracycline-resistant Chlamydia trachomatis strain isolated in Toulouse (France)

Sex Transm Dis. 1998 Aug;25(7):350-2. doi: 10.1097/00007435-199808000-00005.


Background and objectives: We recently reported the first isolation of a tetracycline-resistant Chlamydia trachomatis strain in Toulouse from a woman treated with tetracycline. To characterize this isolate, its in vitro susceptibility was compared with those of 34 other C. trachomatis isolates recovered in Toulouse.

Study design: The susceptibilities of C. trachomatis strains were determined in terms of minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) using McCoy cells in 96-well microdilution plates, with an inoculum of 5.10(3) to 1.10(4) inclusion-forming units/ml. The antimicrobial agents tested were tetracycline, azithromycin, erythromycin, ofloxacin, and pristinamycin.

Results: No difference was observed between the MICs and MBCs except for the tetracycline. Tetracycline-resistant strain MIC and MBC were > 64 micrograms/ml, although < 1% of the bacterial population showed resistance. For the other isolates, the MIC of tetracycline was < or = 0.25 microgram/ml. The antibiotics other than tetracycline were active in vitro against all strains.

Conclusions: These results show that the tetracycline resistance observed in Toulouse differs from the "heterotypic resistance" described previously in the United States in multiresistant C. trachomatis isolates. They confirm that the resistance we observed may be a new phenomenon.

MeSH terms

  • Chlamydia trachomatis / drug effects*
  • Chlamydia trachomatis / isolation & purification
  • Female
  • France
  • Humans
  • Male
  • Microbial Sensitivity Tests
  • Tetracycline Resistance