Development of EIA for detection of Chlamydia trachomatis in genital specimens.

A double antibody sandwich enzyme immunoassay (EIA) for chlamydial antigen detection was developed using a monoclonal antibody against lipopolysaccharide (LPS) of Chlamydia trachomatis as a coating antibody. Polyclonal rabbit antiserum against partially purified antigen from elementary body (EB) antibody and horse-radish peroxidase conjugated goat anti-rabbit antibody were used as the primary and secondary antibody respectively. The developed EIA could detect protein of partially purified EB at the lowest concentration of 250 ng/ml. The assay was evaluated against the cell culture (CC), DNA hybridization assay (PACE2 system: Gen-Probe, San Diego, CA, USA) and a commercial enzyme immunoassay (kEIA) (Bioquest, NSW, Australia). The sensitivity, specificity, positive and negative predictive values of the developed EIA (dEIA) were 87, 96.2, 80, 97.7 for the specimens from females and 90.9, 90.7, 71.4, 97.5 for the specimens from males repectively. Cross reaction was not found with Escherichia coli, Acinetobacter anitratus, beta-Streptococcus group A, Enterobacter spp, Enterococcus, Lactobacillus spp, Neisseria spp, but it was found with Candida albicans and herpes simplex virus type 1. The developed EIA can be applied successfully for both genders, particularly males. The cost per test is less than those for CC, kEIA and PACE2.

An assessment and evaluation of methods for diagnosis of chlamydial and gonococcal infections.

Chlamydia trachomatis and Neisseria gonorrhoeae were studied in 350 females and 140 males attending the sexually transmitted disease clinic and AIDS Center, Khon Kaen zone 6 and the Division of Obstetrics and Gynecology, Khon Kaen Hospital. Chlamydia trachomatis infection was diagnosed by cell culture (CC), enzyme immunoassay (EIA) (Bioquest, NSW, Australia) and nucleic acid hybridization (PACE2 system: Gen-Probe, San Diego, Calif). It was found that the sensitivity, specificity and positive and negative predictive values in females were 95.7, 100.0, 100.0, 99.7% by the cell culture; 91.3, 99.1, 87.5, 99.4% by the EIA; and 78.3, 99.7, 94.7, 98.5% by the PACE2 respectively. Values of the same parameters in males were 83.3, 100.0, 100.0, 98.5% by the cell culture; 75.0, 99.2, 90.0, 97.7% by the EIA and 91.7, 100.0, 100.0, 99.2% by PACE2 respectively. The methods for detection of Neisseria gonorrhoeae infection were conventional culture, PACE2 test and the direct examination (Gram's stain). In females, the sensitivity, specificity and positive and negative predictive values of the conventional culture were 85.7, 100.0, 100.0, 99.7% and those of the PACE2 were 85.7, 99.1, 66.7, 99.7% respectively. In males, the values of the same parameters were 81.8, 100.0, 100.0, 100.0% by the conventional culture, 95.5, 100.0, 100.0 and 99.2% by the PACE2. The prevalence of chlamydial infection in females was 6.6% (23/350) and that in males was 8.6% (12/140). The prevalence of gonococcal infection in females was 2.0% (7/350) and in males was 15.7% (22/140). The co-infection of Chlamydia trachomatis and Neisseria gonorrhoeae in females was 0.9% (3/350) and no co-infection was found in males. It is concluded that cell culture is an appropriate method for detection of Chlamydia trachomatis in both genders, particularly in females. PACE 2 test is the best method for such detection in symptomatic males while EIA is a good method in females, particularly in symptomatic females. For gonococcal detection, PACE2 test is a sensitive, specific and alternative method to the conventional culture. It can be appropriately applied for the diagnosis of gonococcal infection, particularly in males.