title: Molecular methods used to estimate thermal inactivation of a prototype human norovirus: more heat resistant than previously believed?
abstract: Two molecular-based methods for estimating capsid integrity as a proxy for virus infectivity were used to produce thermal inactivation profiles of Snow Mountain virus (SMV), a prototype human norovirus (HuNoV). Monodispersed virus suspensions were exposed to 77, 80, 82 and 85 °C for various times, pre-treated with either propidium monoazide (PMA) or RNase, and subjected to RNA isolation followed by RT-qPCR amplification. D-values were 25.6 ± 2.8, 3.1 ± 0.1, 0.7 ± 0.04 and 0.2 ± 0.07 min at 77, 80, 82 and 85 °C, respectively for PMA-treated SMV; and 16.4 ± 0.4, 3.9 ± 0.2 0.9 ± 0.3 and 0.12 ± 0.00 min at 77, 80, 82 and 85 °C, respectively for RNase-treated SMV. Corresponding zD values were 3.80 °C and 3.71 °C for PMA and RNase-treated virus, respectively. Electron microscopy data applied to heat-treated virus-like particles supported this relatively high degree of thermal resistance. The data suggest that SMV is more heat resistant than common cultivable HuNoV surrogates. Standardized thermal inactivation methods (such as milk pasteurization) may not be stringent enough to eliminate this virus and perhaps other HuNoV.
authors.affiliation: Department of Food, Bioprocessing and Nutrition Sciences, North Carolina State University, Campus Box 7624, Raleigh, NC 27695, USA.
authors.forename: B I
authors.initials: BI
authors.lastname: Escudero-Abarca
authors.affiliation: Department of Food, Bioprocessing and Nutrition Sciences, North Carolina State University, Campus Box 7624, Raleigh, NC 27695, USA.
authors.forename: H
authors.initials: H
authors.lastname: Rawsthorne
authors.affiliation: Department of Food, Bioprocessing and Nutrition Sciences, North Carolina State University, Campus Box 7624, Raleigh, NC 27695, USA. Electronic address: rebecca_goulter@ncsu.edu.
authors.forename: R M
authors.initials: RM
authors.lastname: Goulter
authors.affiliation: Department of Food, Bioprocessing and Nutrition Sciences, North Carolina State University, Campus Box 7624, Raleigh, NC 27695, USA.
authors.forename: S H
authors.initials: SH
authors.lastname: Suh
authors.affiliation: Department of Food, Bioprocessing and Nutrition Sciences, North Carolina State University, Campus Box 7624, Raleigh, NC 27695, USA.
authors.forename: L A
authors.initials: LA
authors.lastname: Jaykus
mesh_terms: D001386:Azides / Q000737:chemistry; D017250:Caliciviridae Infections / Q000821:virology; D006358:Hot Temperature; D006801:Humans; D029322:Norovirus / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification* / Q000502:physiology; D016133:Polymerase Chain Reaction; D011419:Propidium / Q000031:analogs & derivatives / Q000737:chemistry; D012367:RNA, Viral / Q000737:chemistry / Q000235:genetics; D038301:Virus Inactivation
chemical_list: D001386:Azides; D012367:RNA, Viral; C533957:propidium monoazide; D011419:Propidium
keywords: Heat resistance; Human norovirus; Thermal inactivation