Viricidal Efficacy of a 405‐nm Environmental Decontamination System for Inactivation of Bacteriophage Phi6: Surrogate for SARS‐CoV‐2

Abstract

AbstractThe highly transmittable nature of SARS‐CoV‐2 has increased the necessity for novel strategies to safely decontaminate public areas. This study investigates the efficacy of a low irradiance 405‐nm light environmental decontamination system for the inactivation of bacteriophage phi6 as a surrogate for SARS‐CoV‐2. Bacteriophage phi6 was exposed to increasing doses of low irradiance (~0.5 mW cm−2) 405‐nm light while suspended in SM buffer and artificial human saliva at low (~103–4 PFU mL−1) and high (~107–8 PFU mL−1) seeding densities, to determine system efficacy for SARS‐CoV‐2 inactivation and establish the influence of biologically relevant suspension media on viral susceptibility. Complete/near‐complete (≥99.4%) inactivation was demonstrated in all cases, with significantly enhanced reductions observed in biologically relevant media (P < 0.05). Doses of 43.2 and 172.8 J cm−2 were required to achieve ~3 log10 reductions at low density, and 97.2 and 259.2 J cm−2 achieved ~6 log10 reductions at high density, in saliva and SM buffer, respectively: 2.6–4 times less dose was required when suspended in saliva compared to SM buffer. Comparative exposure to higher irradiance (~50 mW cm−2) 405‐nm light indicated that, on a per unit dose basis, 0.5 mW cm−2 treatments were capable of achieving up to 5.8 greater log10 reductions with up to 28‐fold greater germicidal efficiency than that of 50 mW cm−2 treatments. These findings establish the efficacy of low irradiance 405‐nm light systems for inactivation of a SARS‐CoV‐2 surrogate and demonstrate the significant enhancement in susceptibility when suspended in saliva, which is a major vector in COVID‐19 transmission.