Polymerase chain reaction for detection of Chlamydia trachomatis in conjunctival swabs
- aDivision of Virology, Department of Pathological Sciences, University of Manchester, bClinical Virology Laboratory, Manchester Royal Infirmary, Manchester, cRoyal Eye Hospital, Manchester
- Mr Elfath M Elnifro, Clinical Virology, 3rd Floor, Clinical Sciences Building, Manchester Royal Infirmary, Oxford Road, Manchester, M13 9WL.
- Accepted 3 March 1997
Abstract
AIMS/BACKGROUND Ocular Chlamydia trachomatis infection in the west occurs as ophthalmia neonatorum, acquired from the mother, or adult paratrachoma which is also associated with current genital tract infection. Accurate rapid laboratory diagnosis facilitates management, but the relative merits of antigen detection or DNA amplification tests are unresolved.
METHODS A polymerase chain reaction (PCR) test was developed which amplified part of the plasmid shared by all the serovars of C trachomatis. Conjunctival swabs were tested using an in house immune dot-blot test (IDBT) for chlamydial lipopolysaccharide antigen, a commercial direct fluorescent antibody (DFA) test for chlamydial elementary bodies, and the PCR (DNA extracted using guanidinium lysis buffer).
RESULTS The PCR achieved a detection limit of 100 plasmid copies (10 elementary bodies). In a combined retrospective and prospective clinical evaluation, the PCR and IDBT gave identical results with 21 positive and 57 negative eye swabs. However, interpretation of the DFA test required meticulous examination of the stained smear, sometimes by two microscopists.
CONCLUSIONS The PCR is likely to play an increasing role in the diagnosis of ocular C trachomatisinfection because of its excellent sensitivity and specificity.
