Using propidium monoazide to distinguish between viable and nonviable bacteria, MS2 and murine norovirus

AIMS: The ability to distinguish between viable and/or infectious micro-organisms and inactivated cells is extremely important for correctly performing microbial risk assessments. In this study, we evaluated whether propidium monoazide (PMA)-qPCR could distinguish between viable and nonviable bacteria and viruses. METHODS AND RESULTS: A PMA-qPCR combined assay was applied to viable and inactivated bacteria (Escherichia coli and Bacillus subtilis) and viruses (MS2 and murine norovirus [MNV]). PMA, a DNA-intercalating agent, in combination with PCR was better able to distinguish between viable and nonviable bacteria and viruses than conventional PCR. CONCLUSIONS: These results suggest that a combined PMA-qPCR assay can be used to measure the viability of bacterial cells and bacteriophage MS2, but not MNV. SIGNIFICANCE AND IMPACT OF THE STUDY: PMA-qPCR could potentially be used to measure the viability of some micro-organisms, including virus. However, a thorough evaluation should be performed prior to measuring the viability of micro-organisms by PMA-qPCR in a quantitative way.