Detection of Chlamydia trachomatis in culture and urogenital smears by in situ DNA hybridization using a biotinylated DNA probe.

The detection of Chlamydia trachomatis by in situ DNA hybridization in urogenital smears was investigated using a commercially available biotinylated DNA probe. Intracellular staining of inclusion bodies was used as the criterion for positivity. Of 35 patients with a culture proven chlamydial infection 19 had smears in which C. trachomatis was detected by in situ DNA hybridization, indicating a sensitivity of 54%. Of 57 patients with a negative culture, two had positive smears by in situ DNA hybridization. To compare whether the criterion for positivity had influenced the sensitivity obtained with in situ DNA hybridization, 14 duplicate smears from culture positive patients were analysed with in situ DNA hybridization and immunofluorescence. Both methods detected intracellular inclusion bodies in seven of these smears, suggesting that the presence of infected cells mainly determines the sensitivity. The DNA probe did not cross-react with micro-organisms commonly found in the urogenital tract.