Discrimination of infectious bacteriophage T4 virus by propidium monoazide real-time PCR

The advent of quantitative PCR has improved the detection of human viral pathogens in the environment. However, a serious limitation of this method may arise from the inability to discriminate between viruses that are infectious and viruses that have been inactivated and do not represent a human health hazard. To assess whether propidium monoazide (PMA) pre-treatment is a good approach to inhibiting DNA amplification from non-infectious viruses, bacteriophage T4 survival was measured using cell culture titration and real-time PCR with and without PMA pre-treatment. Heat (85 °C) and proteolysis methods were carried out. After these inactivation treatments, the results indicated that the PMA pre-treatment approach is not appropriate for differentiating infectious viruses. However, when a heat treatment at 110 °C was undertaken, PMA pre-treatment did allow differentiation of non-infectious from infectious viruses. In this case, effective binding of PMA to bacteriophage T4 DNA could be taken to indicate capsid damage. Therefore, PMA pre-treatment may be appropriate for assessing effective disinfection treatments and for a more reliable understanding of the factors that contribute to viral inactivation through capsid damage monitoring. The PMA-PCR approach could be useful as a rapid and inexpensive analytical tool for screening and evaluation of the efficacy of disinfectants.