In vitro inhibition of Chlamydia trachomatis growth by liposome-encapsulated cyclines.

The antichlamydial activity of tetracycline (Tet) and doxycycline (Dox) enc apsulated in cationic (CaL), anionic (AnL) and neutral (NtL) liposomes has been evaluated in vitro by adding serial dilutions of antibiotics (minimum inhibitory concentration, MlC: 0.12-0.007 mug/ml; MBC: 4 to 0.25 mug/mi) to HeLa 229 cell monolayers inoculated with Chlamydia trachomatis L-2/434/Bu (10(3) ufi/ml). Following 72 h incubation at 37 degrees C under a 5% CO2 at mosphere, the chlamydial inclusions were stained by the May-Giemsa method t o determine the MICs. After a second and third passage, the MBC1 and MBC2 w ere determined in antibiotic-free medium. The chlamydial inclusions were th en counted to assess the degree of growth inhibition at each antibiotic dil ution tested for MBC1 and MBC2 determinations. The MlC, MBG(1) and MBC2 of the various antichlamydial agents were as follows. Tet (0.12; 4; 4), AnL-Te t (0.01; 1; 1), NtL-Tet (0.03; 1; 2), Dox (0.06; 1; 2), CaL-Dox (0.03; 0.5; 2), AnL-Dox (0.01; 1; 2), and NtL-Dox (0.03; 0.5; 0.5). It was found that Tet and Dox liposome-encapsulated antibiotics were more active than their n on-encapsulated counterparts, and the inclusion count showed a higher inhib itory activity of the former antibiotics on chlamydial growth. The inhibiti on of chlamydial growth by AnL-Tet may be of bactericidal nature. In conclu sion, liposome-encapsulated drugs could be of value in the treatment of chl amydial infections (C) 2001 Editions scientifiques et medicales Elsevier SA S.