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Evaluation of a direct fluorescent antibody assay for detection of Chlamydia pneumoniae
N Miyashita1, A Matsumoto, R Soejima
1Department of Medicine, Kawasaki Medical School, Japan.
Abstract:
We examined the utility of the direct immunofluorescent antibody test kit, IMAGEN (DAKO Diagnostic Co., Ltd.). The stainability of inclusions and purified elementary bodies (EBs) of all the Chlamydia pneumoniae strains used in this study was highly specific. Immunoelectron microscopy and light microscopy of stained EBs revealed the target antigen of IMAGEN to be located on the surface of the EB outer membrane. In a clinical study, we tested oropharyngeal swab specimens obtained from 41 patients (45 specimens). The results were compared with those obtained by isolation in cell culture, the indirect immunofluorescent antibody (IFA) assay and serum antibody titration. C. pneumoniae was isolated from six specimens (13.3%), and the organisms were detected in 11 specimens (24.4%) with IMAGEN and nine specimens (20%) with IFA. A diagnosis of C. pneumoniae infection was made in six patients (13.3%) by the serological examination. Six specimens positive in isolation were positive in the IMAGEN but there were three cases which seemed to be false-positive by the IMAGEN. We conclude that the use of IMAGEN is an easy, rapid and sensitive method for detecting C. pneumoniae when there is a large amount of chlamydial antigen in the clinical specimen and when identification of the chlamydial species forming inclusions in cell cultures is required.
Insights
The IMAGEN direct immunofluorescent antibody test kit shows high specificity for detecting Chlamydia pneumoniae. It is a rapid and sensitive method for identifying chlamydial antigens in clinical specimens.
Area of Science:
- Microbiology
- Immunology
- Diagnostic Assays
Background:
- Chlamydia pneumoniae is a significant respiratory pathogen.
- Accurate and rapid diagnostic methods are crucial for managing C. pneumoniae infections.
Purpose of the Study:
- To evaluate the diagnostic utility of the IMAGEN direct immunofluorescent antibody test kit for Chlamydia pneumoniae detection.
- To assess the specificity and sensitivity of IMAGEN compared to traditional methods.
Main Methods:
- Direct immunofluorescent antibody test (IMAGEN) was used on oropharyngeal swab specimens.
- Results were compared with cell culture isolation, indirect immunofluorescent antibody (IFA) assay, and serum antibody titration.
- Immunoelectron microscopy and light microscopy were used to localize the target antigen.
Main Results:
- IMAGEN demonstrated high specificity for Chlamydia pneumoniae inclusions and elementary bodies (EBs).
- The target antigen was identified on the EB outer membrane surface.
- IMAGEN detected C. pneumoniae in 24.4% of specimens, compared to 13.3% by culture and 20% by IFA.
- Six culture-positive specimens were positive by IMAGEN, with three potential false-positive results.
Conclusions:
- IMAGEN is an easy, rapid, and sensitive method for detecting C. pneumoniae.
- The test is most effective when significant chlamydial antigen is present in specimens.
- IMAGEN aids in identifying the chlamydial species responsible for inclusions in cell cultures.