Indian Journal of Ophthalmology (Jan 1999)
Evaluation of PCR assay for common endogenous plasmid and major outer membrane protein gene of <i>C. trachomatis</i> in diagnosis of follicular conjunctivitis
Abstract
Purpose: To evaluate polymerase chain reaction (PCR) in diagnosis of Chlamydia trachomatis. Methods: In this study PCR assay was used to amplify the 517bp region of common endogenous plasmid in conjunctival specimens from 178 patients with follicular conjuntivitis, and to amplify the 1000bp region of major outer membrane protein (MOMP) gene of C.trachomatis from 71 of these 178 patients. The PCR-amplified products were visualised by agarose gel electrophoresis and ethidium bromide staining and Southern hybridisation with radio-labelled internal probes. The test was compared with a direct immunofluorescence assay using monoclonal antibody for Chlamydia antigen detection. Results: The plasmid PCR assay was positive in 95 (53.37%) of the 178 specimens processed whereas the Chlamydia antigen was detected in 69 (38.76%) of the 178 specimens by direct immunofluorescence assay (p= 0.005). In the 71 specimens processed for both the PCR assays, plasmid PCR was positive in 52 (73.23%) and MOMP PCR was positive in 43 (60.56%) of the specimens (p=0.10). Thirty seven of these 71 specimens which were positive in both PCR assays were also positive in direct immunofluorescence assay. Conclusion: The PCR assays could detect Chlamydia in a significantly larger number of specimens than conventional antigen detection assay, and being marginally more sensitive, the plasmid PCR assay has the potential for wider use in the diagnosis of trachoma.
