Laboratory evaluation of a quaternary ammonium compound (QAC)-based antimicrobial coating used in public transport during the COVID-19 pandemic

Abstract

The virucidal activity of a quaternary ammonium compound (QAC)-based antimicrobial coating used by the UK rail industry during the COVID-19 pandemic was evaluated using the bacteriophage Φ6 as a surrogate for SARS-CoV-2. Immediately after application and in the absence of interfering substance, the product showed efficacy (>3 log10reduction) on some materials typically used in rail carriages (stainless steel, high pressure laminate and plastic), variable efficacy on glass and no efficacy (<3 log10reduction) on a train armrest made of Terluran 22. If, after application of the product, the surfaces remained undisturbed, the antimicrobial coating retained its efficacy for at least 28 days on all materials where it was effective immediately after application. However, regardless of the material coated or time since application, the presence of organic debris (fetal bovine serum) significantly reduced the viricidal activity of the coating. Wiping the surface with a wetted cloth after organic debris deposition was not sufficient to restore efficacy. We conclude that the product is likely to be of limited effectiveness in a busy multi-user environment such as public transport.