Fluorescent, DNA-binding dyes for rapid detection of Chlamydia trachomatis.

The newer DNA-binding fluorochromes DAPI (4',6-diamidino-2-phenylindole) and fluorochrome 33258 H (Hoechst) (2-[2-(4-hydroxy-phenyl)-6-benzimidazolyl]-6-(1-methyl-4-piperazyl)-benzimidazole . 3 HCl) proved useful in identifying genital strains of Chlamydia trachomatis in McCoy cells. For practical purposes, e.g. to analyse patient specimens, we recommend this technique using the fluorochromes at pH 2.0 in a final concentration of 3 micrograms/ml and non-replicative McCoy cells after fixation with alcohol-acetic acid. The application of the fluorochrome technique in demonstrating Chlamydia trachomatis-infections is recommendable because it is a) simple to perform, b) a rapid procedure, c) it corresponded well with the Giemsa staining in identifying mature inclusions, and d) it facilitates the detection of the RNA-rich early stages of chlamydial growth. For this reasons the fluorochrome technique with DAPI or 33258 H at pH 2.0 can be considered a highly specific and sensitive method for identifying Chlamydia trachomatis.