A new confirmatory Neisseria gonorrhoeae real-time PCR assay targeting the porA pseudogene
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The Roche Cobas Amplicor system is widely used for the detection of Neisseria gonorrhoeae but is known to cross react with some commensal Neisseria spp. Therefore, a confirmatory test is required. The most common target for confirmatory tests is the cppB gene of N. gonorrhoeae. However, the cppB gene is also present in other Neisseria spp. and is absent in some N. gonorrhoeae isolates. As a result, laboratories targeting this gene run the risk of obtaining both false-positive and false-negative results. In the study presented here, a newly developed N. gonorrhoeae LightCycler assay (NGpapLC) targeting the N. gonorrhoeae porA pseudogene was tested. The NGpapLC assay was used to test 282 clinical samples, and the results were compared to those obtained using a testing algorithm combining the Cobas Amplicor System (Roche Diagnostics, Sydney, Australia) and an in-house LightCycler assay targeting the cppB gene (cppB-LC). In addition, the specificity of the NGpapLC assay was investigated by testing a broad panel of bacteria including isolates of several Neisseria spp. The NGpapLC assay proved to have comparable clinical sensitivity to the cppB-LC assay. In addition, testing of the bacterial panel showed the NGpapLC assay to be highly specific for N. gonorrhoeae DNA. The results of this study show the NGpapLC assay is a suitable alternative to the cppB-LC assay for confirmation of N. gonorrhoeae-positive results obtained with Cobas Amplicor.
KeywordsPolymerase Chain Reaction Assay Neisseria Gonorrhoeae Throat Swab Polymerase Chain Reaction Detection Clinical Sensitivity
This study was supported by the Royal Children’s Hospital Foundation Grant No. 922-034, which is sponsored by the Woolworths Fresh Futures Campaign. We thank G. Lum and K. Freeman (Pathology Department, Royal Darwin Hospital, Northern Territory), P. Hallsworth (Microbiology Department Flinders Medical Centre, South Australia) and F. Francis (Queensland Health Pathology Service, Townsville General Hospital) for supplying bacterial isolates.
We thank the staff of the Molecular Diagnostic Unit, Microbiology Division, Queensland Health Pathology Service, Royal Brisbane Hospital campus, for supplying the clinical specimens and performing the Roche Cobas Amplicor assay.
This is Sir Albert Sakzewski Virus Research Centre manuscript number 214.
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