Abstract
Abstract Background Chlamydia trachomatis (CT), Neisseria gonorrhoeae (NG), and Trichomonas vaginalis (TV) cause the three most prevalent sexually transmitted infectious diseases in developed countries, contributing to approximately 300 million new infections worldwide, annually. Due to the challenges of culturing and using immunoassays to detect these pathogens, DNA-based molecular tests have been instrumental, and current trends in molecular testing for CT/NG/TV have moved toward point-of-care tests. Lyophilization provides benefits required for point-of-care tests, such as ambient storage, extended shelf life, simplified downstream workflow, and variable formats. A lyophilized-bead format enables an assay to be placed in sealed consumables and stored at room temperature for up to two years. An additional consideration is the need for endogenous and exogenous controls. Exogenous in-process controls can be used to validate the performance of workflows culminating in a qPCR reaction and provide flexibility to test developers. An ideal exogenous in-process control is nonhomologous to human or human pathogen genome sequences and does not align with primers or probes designed for pathogen detection. The objective of the current study was to develop a lyophilized-bead-format assay containing an ideal exogenous control and establish whether it is a valid option for the accurate detection of CT, NG, and TV. Methods A synthetic DNA control containing targets for CT/NG/TV/RNase P (RP)/exogenous control was used to establish an analytical LOD by qPCR. The 5-plex assay, lyophilized in beads, was hydrated and tested for linearity over an 8-log range of the synthetic DNA control. Further, the qPCR lyophilized bead with assay was tested with a proficiency sample by extracting DNA from ZeptoMetrix NATtrol CT/NG/TV Positive Control and spiking-in the exogenous DNA control. qPCR was performed on the extracted DNA and human cDNA. Results The analytical LOD for the control DNA was determined to be 5 copies/reaction. Additionally, linearity was observed by qPCR over an 8-log range of the synthetic DNA control for all five targets in multiplex with good efficiencies and R2 values. Finally, all targets were amplified and detected by qPCR using DNA extracted from ZeptoMetrix NATtrol CT/NG/TV Positive Control with spiked-in exogenous DNA control. The detection of the exogenous sequence in the qPCR multiplex reaction indicated the extraction was successful. Conclusions We have developed a multiplex qPCR assay in lyophilized-bead format that can identify infectious agents, such as CT/NG/TV, in a single reaction. We have included RP as a human host control, plus an exogenous in-process control, for a total of 5-plex in separate fluorescent channels. We have shown that our lyophilized beads with assay produce a positive qPCR result when combined with a proficiency sample.
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