Efficacy of commercial disinfectants Virkon®S and Microchem Plus against poliovirus

Introduction

The WHO Global Action Plan for Poliovirus Containment, 4th edition (GAPIV) describes the necessary conditions for the containment of poliovirus material in poliovirus-essential facilities (PEFs). PEF status is achieved by successfully undergoing the process of certification by the Global Commission for the Certification of the Eradication of Poliomyelitis in compliance with GAPIV requirements. The GAPIV guidelines cover many topics, including waste management, decontamination, disinfection and sterilization. This element of GAPIV requires PEFs to demonstrate in-house validation of decontamination methods with supporting data.

Methods

The method used for validation of chemical products for poliovirus decontamination in this study was based on processes outlined in European Standard EN14476, as recommended by the WHO GAPIV guidelines. In this study, the disinfectants 5 % Microchem Plus and 1 % Virkon®S were evaluated for efficacy against high titre poliovirus in solutions with and without high organic load using an endpoint dilution assay. A poliovirus Sabin 1 strain was used as the reference virus with the titre 8.33 log₁₀ CCID₅₀ (50 % cell culture infectious dose) in 0.1 ml.

Results

The poliovirus titre after Microchem Plus treatment was calculated as 5.5 (representing a 2.8 CCID₅₀ titre reduction), indicating only partial inactivation. In contrast, poliovirus in solutions with and without high organic load achieved >4 log₁₀ CCID₅₀ titre reduction (≥6.8 and ≥5.8 reduction respectively), after Virkon®S treatment. The Virkon®S treatment results were at the limit of detection of the endpoint dilution assay, indicating complete inactivation, or as near complete that can be demonstrated with the assay. The virus culture results were confirmed by a molecular assay for the detection of enterovirus RNA.

Conclusion

Microchem Plus only partially inactivated poliovirus and cannot be relied upon as the sole decontaminant. In contrast, Virkon®S performed well for both high titre poliovirus in solutions with and without high organic load, achieving >4 log₁₀ titre reduction for both, making Virkon®S a suitable disinfectant for poliovirus.