Virkon S beats Microchem Plus against poliovirus in lab test

A study in the Journal of Biosafety and Biosecurity found that 1% Virkon®S met international criteria for inactivating poliovirus, while 5% Microchem Plus fell short. The results matter for poliovirus-essential facilities that must validate decontamination methods under WHO containment rules.

Why it matters: - Poliovirus-essential facilities must prove their decontamination methods can neutralize a non-enveloped virus that resists many routine disinfectants. - The findings point to one commercial disinfectant that can support containment work and one that should not be used alone. - The study is tied to the WHO Global Action Plan for Poliovirus Containment, which sets expectations for facility-level validation.

What happened: - Researchers evaluated 5% Microchem Plus and 1% Virkon®S against high-titer Sabin 1 poliovirus. - The work used the European EN14476 framework, as recommended in WHO GAPIV guidance. - Testing was published in the Journal of Biosafety and Biosecurity. - The study used an initial virus titre of 8.33 log10 CCID50 per 0.1 mL. - The team tested virus in clean solution and in a faecal suspension designed to simulate high organic load.

The details: - Microchem Plus was tested with a 20-minute contact time. - Virkon®S was tested with a 10-minute contact time. - Microchem Plus only partially inactivated poliovirus. - After 20 minutes, residual virus titre remained at 5.5 log10 CCID50. - That translated to a 2.8 log10 reduction, below the 4 log10 reduction level needed for PEF disinfection. - Secondary cell passaging and RT-qPCR still detected viable viral material after Microchem Plus treatment. - Virkon®S reduced virus to 1.5 log10 CCID50 or lower in high-titer samples. - That amounted to at least a 6.8 log reduction in clean conditions. - Virkon®S still produced at least a 5.8 log reduction in the high-organic-load samples. - No cytopathic effect or amplifiable viral RNA was recovered after two rounds of cell culture following Virkon®S treatment. - The DOI for the paper is 10.1016/j.jobb.2025.08.002.

Between the lines: - The results reinforce a broader pattern: quaternary ammonium compounds often perform poorly against non-enveloped enteroviruses. - Virkon®S offers a stronger fit for biosafety settings because it remains active in organic matter and is less corrosive and toxic than bleach, formaldehyde or glutaraldehyde. - The data also suggest that disinfection choice has to match the use case, not just the pathogen. - Virkon®S has limits: the working solution expires within five days, and long exposure can mildly corrode metal. - That makes it better suited for bench surfaces, small labware and spill cleanup than for immersion tanks or chemical showers.

What's next: - Facilities that rely on immersion tanks or chemical showers may need combined disinfection workflows instead of a single-product approach. - The study gives containment labs a practical option for updating poliovirus decontamination protocols. - The findings may shape how PEFs document compliance with WHO containment requirements.

The bottom line: - Microchem Plus is not reliable as a standalone poliovirus decontaminant, while Virkon®S met the study's efficacy benchmark for both clean and high-organic-load conditions.