In vitro antichlamydial activity of antimicrobials and quinolones using a rapid microtiter screening test system

The activities of twelve antimicrobials against Chlamydia trachomatis were compared when determined in a cell culture system by shell vial and by a rapid microtiter assay. The minimal inhibitory concentration of nine of the twelve were identical in both assays and ranged from 0.03 to > 512 μg/ml. The other three differed by one two-fold dilution from shell vial to microtiter assay and had MICs which ranged from 0.015 to 0.8 μg/ml. The activities of eleven quinolones against Chlamydia trachomatis were measured in vitro by microtiter assay. The minimum inhibitory concentrations of the eleven obtained by microtiter assay ranged from 0.5 to > 1024 μg/ml and were comparable to published shell vial values. The microtiter method, which is easier and less time consuming to carry out, gives comparable activities to the longer shell vial system.