Efficacy and Mechanisms of Murine Norovirus Inhibition by Pulsed-Light Technology

Pulsed light is a nonthermal processing technology recognized by the FDA for killing microorganisms on food surfaces, with cumulative fluences up to 12 J cm(-2). In this study, we investigated its efficacy for inactivating murine norovirus 1 (MNV-1) as a human norovirus surrogate in phosphate-buffered saline, hard water, mineral water, turbid water, and sewage treatment effluent and on food contact surfaces, including high-density polyethylene, polyvinyl chloride, and stainless steel, free or in an alginate matrix. The pulsed-light device emitted a broadband spectrum (200 to 1,000 nm) at a fluence of 0.67 J cm(-2) per pulse, with 2% UV at 8 cmbeneath the lamp. Reductions in viral infectivity exceeded 3 log(10) in less than 3 s (5 pulses; 3.45 J cm(-2)) in clear suspensions and on clean surfaces, even in the presence of alginate, and in 6 s (11 pulses; 7.60 J cm(-2)) on fouled surfaces except for stainless steel (2.6 log(10)). The presence of protein or bentonite interfered with viral inactivation. Analysis of the morphology, the viral proteins, and the RNA integrity of treated MNV-1 allowed us to elucidate the mechanisms involved in the antiviral activity of pulsed light. Pulsed light appeared to disrupt MNV-1 structure and degrade viral protein and RNA. The results suggest that pulsed-light technology could provide an effective alternative means of inactivating noroviruses in wastewaters, in clear beverages, in drinking water, or on food-handling surfaces in the presence or absence of biofilms.