Rapid detection of Chlamydia trachomatis

Absence of Chlamydia in trachomatous lacrimal sacs

We performed lacrimal sac biopsies in 35 patients who underwent dacryocystohinostomies in Saudi Arabia. The nasolacrimal duct obstructions were presumably secondary to trachoma in 22 cases and unknown in the remaining 13 cases. Lacrimal sac specimens were submitted for routine histopathologic examination and the direct-smear fluorescent antibody test. All specimens were negative for chlamydia. Possible reasons for the low detection rate of chlamydia in the trachomatous group were the frequent finding of clinically inactive disease, common canalicular obstruction, and loss of the epithelial lining in the lacrimal sac.

Comparison of a fluorescent monoclonal antibody assay and a tissue culture assay for routine detection of infections caused by Chlamydia trachomatis

The applicability of a commercial direct immunofluorescent monoclonal antibody assay for detection of Chlamydia trachomatis elementary bodies was studied on endocervical smears from 506 women attending a venereal disease clinic. The aim of this prospective examination was to simulate a daily routine. The results were compared to those of a well-functioning tissue culture assay. The overall positivity was 22.7%. Based on a positivity criterion of greater than or equal to 1 elementary body in the fluorescent antibody assay, the two assays agreed in 84.8% of the cases. In 50 specimens the antibody assay was positive and the culture assay negative, whereas in 23 the culture assay was positive and the antibody assay negative. The positive predictive value was 63.8%. Most of the discrepancies were found in specimens containing few elementary bodies or inclusions. Based on a criterion of greater than or equal to 10 elementary bodies, the positive predictive value was 70.9%, but the sensitivity fell to 67.5%.

Comparison of direct immunofluorescence and cell culture for detecting Chlamydia trachomatis

Conventional cell culture methods were compared with a direct immunofluorescence test (MicroTrak, Syva UK, Maidenhead, Berkshire) to detect Chlamydia trachomatis in 137 patients (126 women, 11 men) attending a sexually transmitted diseases (STD) clinic. Results obtained by the two tests agreed in 87.6% of cases. Of 34 positive specimens, 17 were detected by culture and fluorescence, 15 by fluorescence only, and two by culture only. The excess of specimens that were negative on culture but positive on fluorescence might be accounted for by delays in culture (up to 18 hours). The MicroTrak test appears to be of value in peripheral hospitals that have to rely on transporting specimens to larger centres for culture.