Survival of Calicivirus in Foods and on Surfaces: Experiments with Feline Calicivirus as a Surrogate for Norovirus

116

Noroviruses (NoV) are the major cause of nonbacterial gastroenteritis. However, there is no published study to ascertain their survival on foodstuffs which are directly related to human health risk. In the present study, we developed a rapid, simple, and sensitive real-time nucleic acid sequence-based amplification (NASBA) combined with an enzymatic treatment for distinguishing infectious from noninfectious human NoV. The developed method was validated using spiked ready-to-eat food samples. When feline calicivirus (FCV) was used as a NoV surrogate in the preliminary assays, it appeared more sensitive to heat inactivation and enzymatic pretreatment than the human NoV. This suggests that FCV may not be an ideal model for studying NoV. Our results reveal clearly that the developed enzymatic pretreatment/real-time NASBA combination successfully distinguished the infectious from heat-inactivated NoV. Moreover, we demonstrate that NoV survived for at least 10 days on refrigerated ready-to-eat foods, such as lettuce and turkey. However, the survival rate was higher on turkey than on lettuce, probably because of their different surface natures. The approach developed in this study may be suitable for more in-depth studies of the persistence and inactivation of human NoV and may be applied to other nonculturable RNA viruses. Moreover, the evaluation of infectious NoV survival provided valuable information concerning its persistence on ready-to-eat food.

Section: Discussionsupporting

confidence: 84%

Section: Discussionmentioning

confidence: 99%

Evaluation of the Persistence of Infectious Human Noroviruses on Food Surfaces by Using Real-Time Nucleic Acid Sequence-Based Amplification

Lamhoujeb

Fliss

Ngazoa

et al. 2008

116

“…In addition, food such as vegetables and soft fruit can be contaminated earlier in the food chain, e.g., via virus-contaminated irrigation water (2,4). Once in food ingredients, HuNoV can probably persist on food for extended periods under frozen and cooled conditions, as well as at room temperature, as was shown in HuNoV surrogate studies (5,6). Several attributes of HuNoV, such as a high virus load in the vomit and feces of infected individuals, a prolonged virus-shedding time, a small infective dose of the virus, and high environmental stability, all facilitate virus transmission from the environment and foods to humans (7).…”

mentioning

confidence: 99%

Norovirus Transmission between Hands, Gloves, Utensils, and Fresh Produce during Simulated Food Handling

Rönnqvist

Aho

Mikkelä

et al. 2014

cHuman noroviruses (HuNoVs), a leading cause of food-borne gastroenteritis worldwide, are easily transferred via ready-to-eat (RTE) foods, often prepared by infected food handlers. In this study, the transmission of HuNoV and murine norovirus (MuNoV) from virus-contaminated hands to latex gloves during gloving, as well as from virus-contaminated donor surfaces to recipient surfaces after simulated preparation of cucumber sandwiches, was inspected. Virus transfer was investigated by swabbing with polyester swabs, followed by nucleic acid extraction from the swabs with a commercial kit and quantitative reverse transcription-PCR. During gloving, transfer of MuNoV dried on the hand was observed 10/12 times. HuNoV, dried on latex gloves, was disseminated to clean pairs of gloves 10/12 times, whereas HuNoV without drying was disseminated 11/12 times. In the sandwich-preparing simulation, both viruses were transferred repeatedly to the first recipient surface (left hand, cucumber, and knife) during the preparation. Both MuNoV and HuNoV were transferred more efficiently from latex gloves to cucumbers (1.2% ؎ 0.6% and 1.5% ؎ 1.9%) than vice versa (0.7% ؎ 0.5% and 0.5% ؎ 0.4%). We estimated that transfer of at least one infective HuNoV from contaminated hands to the sandwich prepared was likely to occur if the hands of the food handler contained 3 log 10 or more HuNoVs before gloving. Virus-contaminated gloves were estimated to transfer HuNoV to the food servings more efficiently than a single contaminated cucumber during handling. Our results indicate that virus-free food ingredients and good hand hygiene are needed to prevent HuNoV contamination of RTE foods.

“…The survival of these viruses may differ between preharvest and postharvest environments, and survival on the leaf surfaces may differ from that within the leaf tissues. Multiple studies that have investigated the postharvest survival of HuNoV on fresh produce have shown that this virus or its calicivirus surrogates (MNV, SaV, and TV) can survive during the chilling storage period and well beyond the produce shelf life (17,30,(39)(40)(41)(42). For example, HuNoV inoculated onto cut lettuce pieces persisted at 4°C for the entire 14-day study period with only a 1-to 1.5-log-unit reduction in RNA titers (39).…”

Section: Discussionmentioning

confidence: 99%

Abiotic Stress and Phyllosphere Bacteria Influence the Survival of Human Norovirus and Its Surrogates on Preharvest Leafy Greens

Esseili

Gao

Tegtmeier

et al. 2016

Foodborne outbreaks of human noroviruses (HuNoVs) are frequently associated with leafy greens. Because there is no effective method to eliminate HuNoV from postharvest leafy greens, understanding virus survival under preharvest conditions is crucial. The objective of this study was to evaluate the survival of HuNoV and its surrogate viruses, murine norovirus (MNV), porcine sapovirus (SaV), and Tulane virus (TV), on preharvest lettuce and spinach that were subjected to abiotic stress (physical damage, heat, or flood). We also examined the bacteria culturable from the phyllosphere in response to abiotic stress and in relation to viral persistence. Mature plants were subjected to stressors 2 days prior to inoculation of the viruses on leaves. We quantified the viral RNA, determined the infectivity of the surrogates, and performed bacterial counts on postinoculation days (PIDs) 0, 1, 7, and 14. For both plant types, time exerted significant effects on HuNoV, MNV, SaV, and TV RNA titers, with greater effects being seen for the surrogates. Infectious surrogate viruses were undetectable on PID 14. Only physical damage on PID 14 significantly enhanced HuNoV RNA persistence on lettuce, while the three stressors differentially enhanced the persistence of MNV and TV RNA. Bacterial counts were significantly affected by time and plant type but not by the stressors. However, bacterial counts correlated significantly with HuNoV RNA titers on spinach and with the presence of surrogate viruses on both plant types under various conditions. In conclusion, abiotic stressors and phyllosphere bacterial density may differentially influence the survival of HuNoV and its surrogates on lettuce and spinach, emphasizing the need for the use of preventive measures at the preharvest stage.H uman noroviruses (HuNoVs) are the leading cause of acute gastroenteritis and foodborne illnesses in the United States, causing 19 million to 21 million cases, 570 to 800 deaths, and $777 million in health care-associated costs annually (1). These singlestranded RNA viruses belong to the Caliciviridae family and are 28 to 35 nm in diameter and nonenveloped. Although these viruses cause self-limiting gastroenteritis, more serious infections can develop in high-risk groups, such as the elderly and immunocompromised populations (2). The virus is mainly transmitted to humans via the fecal-oral route either by contact with an infected person or fomites or by ingestion of contaminated food and water (2). Leafy greens are frequently associated with HuNoV outbreaks (1) and are globally recognized to be a high priority in terms of the microbial safety of fresh produce (3). Contamination of leafy greens with HuNoVs can occur at any stage along the farm-to-fork chain (3) through a number of sources, including fecally contaminated water used for irrigation, improperly treated sewage sludge used for fertilization, and food harvesters or food handlers who use improper hygiene practices (4, 5). Because HuNoVs have a low infectious dose (ϳ18 to 1,000 viral particles) (6) ...