Korean Journal of
Veterinary Service

In virucidal efficacy testing, the chemical inactivation cannot be determined for all viruses due to the difficulties or the inability to culture sufficiently or the risk of exposure to the viruses. Therefore, disinfectants against these viruses could be evaluated by different methods and surrogate viruses are used as alternative. In this study we developed a method for efficacy testing of veterinary disinfectants using one of the candidate surrogate viruses, bacteriophage MS2, as part of the research on the selection of surrogate viruses for efficiency of efficacy testing of veterinary disinfectants. This method is based on the Animal and Plant Quarantine Agency (APQA) guidelines for efficacy testing of veterinary disinfectants. Bacteriophage and disinfectant are reacted in suspension in accordance with the APQA guidelines and then a newly established double agar layer method is applied for the efficacy test. The double agar layer method is summarized as follows: 1) The bottom agar with 1.5% agar is boiled and cooled before poured into petri dishes at volume of 20 mL, and dried under biological safety cabinet. 2) The top agar with 0.7% agar is boiled and kept at 50℃ before E. coli culture was seeded. 3) The serially diluted bacteriophage MS2-disinfectant mixtures 0.05 mL and E. coli host 0.01 mL (OD₆₀₀ 0.2~0.3) are mixed with 5 mL of top agar and incubate them at 50℃ for 5 min for reaction. 4) The resulting mixture is poured over top of a bottom agar plate and rocked sufficiently to ensure that the top agar covers the entire surface of the bottom agar. 5) The double agar layer is then placed under biological safety cabinet to allow the agar layer to solidify and subsequently incubated at 37℃ for 24 hr. 6) Following incubation, the plates may be inspected for plaques and record results.

Keywords Bacteriophage MS2, Disinfectant, Double agar layer method, Virucidal efficacy

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