The Efficacy of Commercial Surface Sanitizers against Norovirus on Formica Surfaces with and without Inclusion of a Wiping Step

Abstract

Commonly used surface sanitizers often lack activity against human noroviruses (hNoVs). The impact of inactivation versus removal when these products are applied via wiping is poorly characterized. The purpose of this work was to assess the anti-hNoV efficacy of various surface sanitizer chemistries, as applied to a laminate material commonly used for restaurant tabletops, using standard surface assays (ASTM E1053-11) and a newly developed wiping protocol. Four commercially available products with different active ingredient(s) (i.e., ethanol [EtOH], acid + anionic surfactant [AAS], quaternary ammonium compound [QAC], and sodium hypochlorite [NaOCl]) and a water control were evaluated against hNoV GII.4 Sydney, hNoV GI.6, and the cultivable surrogate Tulane virus (TuV). Virus concentration was evaluated using RNase-reverse transcriptase (RT)-quantitative PCR (qPCR) (hNoV) and infectivity assay (TuV). Only the EtOH-based product significantly reduced virus concentration (>3.5 log₁₀ reduction [LR]) by surface assay, with all other products producing ≤0.5 LR. The inclusion of a wiping step enhanced the efficacy of all products, producing complete virus elimination for the EtOH-based product and 1.6 to 3.8 LR for the other chemistries. For hNoVs, no detectable residual virus could be recovered from paper towels used to wipe the EtOH-based product, while high concentrations of virus could be recovered from the used paper towel and the wiped coupon (1.5 to 2.5 log₁₀ lower genome equivalent copies [GEC] compared to control) for the QAC- and AAS-based products and for water. These results illustrate the variability in anti-hNoV activity of representative surface sanitizers and highlights the value of wiping, the efficacy of which appears to be driven by a combination of virus inactivation and removal. IMPORTANCE Human noroviruses (hNoVs) are the leading cause of acute gastroenteritis and food-borne disease worldwide. Noroviruses are difficult to inactivate, being recalcitrant to sanitizers and disinfectants commonly used by the retail food sector. This comparative study demonstrates the variability in anti-hNoV activity of representative surface sanitizers, even those allowed to make label claims based on the cultivable surrogate, feline calicivirus (FCV). It also highlights the importance of wiping in the process of sanitization, which significantly improves product efficacy through the action of physical removal of surface microbes. There is a need for more and better product formulations with demonstrated efficacy against hNoVs, which will likely necessitate the use of alternative cultivable surrogates, such as Tulane virus (TuV). These findings help food safety professionals make informed decisions on sanitizing product selection and application methods in order to reduce the risk of hNoV contamination and transmission in their facilities.

Keywords: Tulane virus; disinfect; human norovirus; sanitize; wiping.

FIG 1

Log₁₀ reduction of GII.4 human norovirus (hNoV) genome equivalent copies (GECs) by various sanitizing products and contact times (30 and 60 s) on Formica coupons without (a, b) and with (c, d) a wiping step with paper towel. The dotted line for each panel represents the limit of detection of the assay. Different letters within a panel represent significant statistical differences (P < 0.05) in the log₁₀ reduction of GII.4 hNoV GEC when comparing products within that panel. Asterisks used in the margin above panels c and d indicate situations in which a statistically significant (P < 0.05) increase in log₁₀ reduction of GII.4 hNoV GEC occurred as a result of incorporating a wiping step into the process. Error bars represent the standard deviation. EtOH, ethanol; AAS, acid + anionic surfactant; NaOCl, sodium hypochlorite; QAC, quaternary ammonium compound.

FIG 2

Log₁₀ reduction of GI.6 hNoV GEC by various sanitizing products and contact times (30 and 60 s) on Formica coupons without (a, b) and with (c, d) a wiping step with paper towel. The dotted line for each panel represents the limit of detection of the assay. Different letters within a panel represent significant statistical differences (P < 0.05) in the log₁₀ reduction of GI.6 hNoV GEC when comparing products within that panel. Asterisks used in the margin above panels c and d indicate situations in which a statistically significant (P < 0.05) increase in log₁₀ reduction of GI.6 hNoV GEC occurred as a result of incorporating a wiping step into the process. Error bars represent the standard deviation. EtOH, ethanol; AAS, acid + anionic surfactant; NaOCl, sodium hypochlorite; QAC, quaternary ammonium compound.

FIG 3

Log₁₀ reduction of Tulane virus (TuV) PFU by various sanitizing products and contact times (30 and 60 s) on Formica coupons without (a, b) and with (c, d) a wiping step with paper towel. The dotted line for each panel represents the limit of detection of the assay. Different letters within a panel represent significant statistical differences (P < 0.05) in the log₁₀ reduction of TuV PFU when comparing products within that panel. Asterisks used in the margin above panels c and d indicate situations where a statistically significant (P < 0.05) increase in log₁₀ reduction of TuV PFU occurred as a result of incorporating a wiping step into the process. Error bars represent the standard deviation. EtOH, ethanol; AAS, acid + anionic surfactant; NaOCl, sodium hypochlorite; QAC, quaternary ammonium compound.

FIG 4

Log₁₀ recoveries of GII.4 hNoV GEC (a), GI.6 hNoV GEC (b), and TuV PFU (c) from paper towels following treatment of virus-inoculated Formica surfaces with various surface sanitizers applied with a paper towel wiping step. Controls represent the viral titer of dried inocula on untreated coupons. The dotted line represents the limit of detection of the assay. Different letters within a column of panels represent significant statistical differences (P < 0.05) in the log₁₀ recovery of virus when comparing sanitizing products, with lowercase letters being used for 30 s and uppercase letters being used for 60 s. EtOH, ethanol; AAS, acid + anionic surfactant; NaOCl, sodium hypochlorite; QAC, quaternary ammonium compound.