Determination of the Thermal Inactivation Kinetics of the Human Norovirus Surrogates, Murine Norovirus and Feline Calicivirus

Human norovirus (NoV) is the major causative agent of fresh-produce-related outbreaks of gastroenteritis; however, the ecology and persistence of human NoV in produce systems are poorly understood. In this study, the effects of abiotic and biotic stresses on the internalization and dissemination of two human NoV surrogates (murine norovirus 1 [MNV-1] and Tulane virus [TV]) in romaine lettuce were determined. To induce abiotic stress, romaine lettuce was grown under drought and flood conditions that mimic extreme weather events, followed by inoculation of soil with MNV-1 or TV. Independently, lettuce plants were infected with lettuce mosaic virus (LMV) to induce biotic stress, followed by inoculation with TV. Plants were grown for 14 days, and viral titers in harvested tissues were determined by plaque assays. It was found that drought stress significantly decreased the rates of both MNV-1 and TV internalization and dissemination. In contrast, neither flood stress nor biotic stress significantly impacted viral internalization or dissemination. Additionally, the rates of TV internalization and dissemination in soil-grown lettuce were significantly higher than those for MNV-1. Collectively, these results demonstrated that (i) human NoV surrogates can be internalized via roots and disseminated to shoots and leaves of romaine lettuce grown in soil, (ii) abiotic stress (drought) but not biotic stress (LMV infection) affects the rates of viral internalization and dissemination, and (iii) the type of virus affects the efficiency of internalization and dissemination. This study also highlights the need to develop effective measures to eliminate internalized viruses in fresh produce. Human norovirus (NoV) is the major cause of nonbacterial gastroenteritis, contributing to Ͼ95% of nonbacterial acute gastroenteritis worldwide and Ͼ60% of all food-borne illnesses reported annually in the United States (1-4). High-risk foods for human NoV contamination include fresh produce, shellfish, and ready-to-eat foods. As individuals are increasingly striving to achieve healthier diets, the consumption of fresh produce has increased in recent years, and fresh produce is now recognized as a leading cause of food-borne illness in the United States (5, 6). Human NoV alone accounts for more than 40% of the freshproduce-related illnesses reported each year in the United States (1, 2, 4, 6-9). Outbreaks in many diverse types of produce, including fresh cut fruit, lettuce, tomatoes, melons, salads, green onions, strawberries, blueberries, raspberries, and salsa, have been attributed to human NoV (6, 7, 10-15). Human NoV is highly infectious, is resistant to common disinfectants, has a low infectious dose, and is highly stable in the environment, all features that contribute to the high prevalence of food-borne outbreaks associated with the virus and its presence and persistence in food commodities (3,5,7,(16)(17)(18)(19).Fresh produce can become contaminated with human NoV at any step from production to processing. In a survey of the point of...

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confidence: 99%

Effects of Abiotic and Biotic Stresses on the Internalization and Dissemination of Human Norovirus Surrogates in Growing Romaine Lettuce

DiCaprio

Purgianto

Lǐ

2015

“…Thus, the choice of the most appropriate model is crucial to gather correct information about the thermal inactivation kinetic behavior of the target pathogen. Recent studies conducted on thermal inactivation of HNoV surrogates (21)(22)(23)(24)(25) and HAV (26,27) revealed that the Weibull model was statistically superior to the first-order model in describing the thermal inactivation kinetics of HNoV surrogates and HAV.…”

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confidence: 99%

Thermal Inactivation Kinetics of Human Norovirus Surrogates and Hepatitis A Virus in Turkey Deli Meat

Bozkurt

D’Souza

Davidson

2015

Self Cite

4), in a publication on the incidence and causes of foodborne illnesses in the United States, reported that a large number of outbreaks are caused by HNoV (58%). Additionally, relatively high hospitalization and death rates are associated with HAV infection (32% and 2%, respectively) (1, 4).According to the U.S. Food and Drug Administration (FDA) and U.S. Department of Agriculture Food Safety and Inspection Service (FSIS), deli meat has posed the highest per annum risk of illness and death among poultry products (5). Additionally, in other studies, Gould et al. (6) and Painter et al. (7) studied surveillance and attribution of foodborne disease outbreaks in the United States from 1998 to 2008. They found that, among individual food categories, poultry was the most commonly reported food vehicle of disease, causing 17% of outbreaks of foodborne illness (6), and that the proportions of poultry-associated foodborne illnesses, hospitalizations, and deaths caused by human noroviruses and HAV were 28%, 14%, and 4%, respectively (7). In 1998 through 2002 alone, three large outbreaks were linked to the consumption of turkey delicatessen meat contaminated during processing (7). Since ready-to-eat (RTE) meat and poultry deli products can be consumed without further cooking, these products should be free of non-spore-forming pathogens following the industrial thermal process. However, they can become contaminated before packaging in the final retail wrap and thus pose a safety threat for consumers (8,9). Viral contamination of RTE and prepared foods most frequently comes from poor hand-washing practices of food handlers after toilet use. Fecal material can be left on hands or even under nails which then can come in contact with food products (10). Handling cooked products with bare hands has been identified as a major factor for pathogen transfer to RTE foods (11), and there is presumed to be a direct correlation between the number of pathogenic organisms on a food employee's hands and the probability of microbial transfer from hands to cooked food products (12). Since the contamination most likely occurs at the surface, it seems advisable to decontaminate the outer layer of products. For this purpose, postpackage pasteurization technologies could be practiced as a method for reducing surface contamination by food pathogens (9). One of the challenges for the industry would be to assess the required time and temperature combination, which would depend on the thermal inactivation kinetics of the target microorganism (13). It has been reported that foodborne enteric viruses are more heat resistant than most non-spore-forming bacterial foodborne pathogens (14); thus, processing recommendations based on the data for non-spore-forming bacteria may not eliminate similar numbers of foodborne enteric viruses. Since there is no specific federal regulation covering the minimum time-temperature combinations for inactivating virus in contaminated deli meat, establishment of potential thermal processes for inactivating human norovirus...

“…With the discovery of murine norovirus (MNV) in 2003 (16), many researchers are now using this newly described virus, because it is genetically more closely related to human noroviruses and is resistant to low pHs (17,18). Many studies comparing FCV and MNV with or without other surrogates, such as MS2 coliphage and hepatitis A virus, as well as human norovirus (using reverse transcription-quantitative PCR [RT-qPCR]), have been published (4,(18)(19)(20)(21)(22)(23)(24). However, because MNV is highly sensitive to alcohols (18), the focus has expanded to cultivable calici-viruses such as TuV (14,(25)(26)(27)(28) and to porcine enteric calicivirus (PEC), a genogroup III (GIII) sapovirus (29,30).…”

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confidence: 99%

Comprehensive Comparison of Cultivable Norovirus Surrogates in Response to Different Inactivation and Disinfection Treatments

Cromeans

Park

Costantini

et al. 2014

172

174

g Human norovirus is the leading cause of epidemic and sporadic acute gastroenteritis. Since no cell culture method for human norovirus exists, cultivable surrogate viruses (CSV), including feline calicivirus (FCV), murine norovirus (MNV), porcine enteric calicivirus (PEC), and Tulane virus (TuV), have been used to study responses to inactivation and disinfection methods. We compared the levels of reduction in infectivities of CSV and Aichi virus (AiV) after exposure to extreme pHs, 56°C heating, alcohols, chlorine on surfaces, and high hydrostatic pressure (HHP), using the same matrix and identical test parameters for all viruses, as well as the reduction of human norovirus RNA levels under these conditions. At pH 2, FCV was inactivated by 6 log 10 units, whereas MNV, TuV, and AiV were resistant. All CSV were completely inactivated at 56°C within 20 min. MNV was inactivated 5 log 10 units by alcohols, in contrast to 2 and 3 log 10 units for FCV and PEC, respectively. TuV and AiV were relatively insensitive to alcohols. FCV was reduced 5 log 10 units by 1,000 ppm chlorine, in contrast to 1 log 10 unit for the other CSV. All CSV except FCV, when dried on stainless steel surfaces, were insensitive to 200 ppm chlorine. HHP completely inactivated FCV, MNV, and PEC at >300 MPa, and TuV at 600 MPa, while AiV was completely resistant to HHP up to 800 MPa. By reverse transcription-quantitative PCR (RT-qPCR), genogroup I (GI) noroviruses were more sensitive than GII noroviruses to alcohols, chlorine, and HHP. Although inactivation profiles were variable for each treatment, TuV and MNV were the most resistant CSV overall and therefore are the best candidates for studying the public health outcomes of norovirus infections.