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


METHODS
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.
Laboratoire de Prévention des Maladies Transmissibles Sexuellement, Faculté de Médecine Purpan, Toulouse, France.
J C
JC
Lefèvre
J P
JP
Lépargneur
D002692:Chlamydia trachomatis / Q000187:drug effects* / Q000302:isolation & purification; D005260:Female; D005602:France; D006801:Humans; D008297:Male; D008826:Microbial Sensitivity Tests; D013753:Tetracycline Resistance