QUANTITATION OF CHLAMYDIA-TRACHOMATIS BY CULTURE, DIRECT IMMUNOFLUORESCENCE AND COMPETITIVE POLYMERASE CHAIN-REACTION

Objectives-Methods to quantitate Chlamydia trachomatis have never been compared although it would be relevant to periodically evaluate the s ensitivity of a detection system. We compared the sensitivity and repr oducibility of culture, direct immunofluorescence and the polymerase c hain reaction (PCR) to quantitate C trachomatis. Methods-A competitive semiquantitative PCR procedure was developed. The number of inclusion s in culture, particles by direct immunofluorescence and DNA copies by PCR were measured for 12 patient specimens. Variation was determined by measuring a sample 10 times for each method. Results-Patient C trac homatis major outer membrane protein gene DNA was measured semiquantit atively by amplifying together with reference DNA. DNA molecules, part icles and infectious units were quantitated in clinical samples with, on average, 595 DNA molecules and 87 immunofluorescent particles obser ved per inclusion-forming-unit. Similar coefficients of variation (47- 52%) were observed for the 3 procedures. Conclusion-Competitive PCR an d counting immunofluorescent particles provide reproducible and sensit ive methods of quantitating C trachomatis.