Commercially available fluorescein-conjugated monoclonal antibody for determining the in vitro activity of antimicrobial agents against Chlamydia trachomatis.

A simple, reproducible method for determining the antibiotic susceptibility of chlamydial isolates is described. Minimum inhibitory and lethal concentrations (MICs and MLCs) were determined for tetracycline and erythromycin titrated against a recent clinical isolate of Chlamydia trachomatis in McCoy cell cultures. A fluorescent antibody stain was found to be more sensitive than giemsa staining, generally giving two-fold higher values for both MICs and MLCs.