A versatile internal control for use as DNA in real-time PCR and as RNA in real-time reverse transcription PCR assays

Aims: To develop and evaluate a TaqMan-based internal amplification control (IAC) that can be used as DNA in real-time PCR (qPCR) or as RNA in reverse transcription real-time PCR (qRT-PCR) to identify the presence of assay inhibition and to evaluate its incorporation into existing qPCR and qRT-PCR methods for bacterial detection. Methods and Results: A DNA IAC was constructed by generating a 198-bp random sequence that was synthesized and inserted into a pZErO-2 vector and transformed into Escherichia coli. The RNA IAC was generated through in vitro transcription of the DNA IAC. Both IAC formats were tested individually in singleplex TaqMan reactions and also included in existing multiplex assays. The DNA IAC was incorporated in a Shigella spp. detection qPCR assay (targeting ipaH). The RNA IAC was successfully evaluated in a Salmonella spp. detection qRT-PCR (using invA mRNA as target). Conclusions: A highly versatile IAC that can be supplemented to qPCR and qRT-PCR pathogen detection methods was developed, greatly reducing the confounding effects of false negatives because of PCR inhibitors without affecting pathogen detection. Significance and Impact of the Study: The frequency of false negatives associated with qPCR analyses is prevalent in certain matrices, particularly those involving complex foods. Hence, the IAC presented here provides a solution to unforeseen false-negative reactions in PCR.