Skip to main page content

• HOME
• Current Issue
• Archive
• Alerts
• About ASM
• Contact us
• Tech Support
• Journals.ASM.org

This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Reprints and Permissions Copyright Information Books from ASM Press MicrobeWorld Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Kingsley, D. H. Articles by Flick, G. J. Search for Related Content PubMed PubMed Citation Articles by Kingsley, D. H. Articles by Flick, G. J. Agricola Articles by Kingsley, D. H. Articles by Flick, G. J.

 Previous Article  |  Next Article 

Applied and Environmental Microbiology, January 2007, p. 581-585, Vol. 73, No. 2
0099-2240/07/$08.00+0     doi:10.1128/AEM.02117-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Inactivation of a Norovirus by High-Pressure Processing

David H. Kingsley,^1* Daniel R. Holliman,² Kevin R. Calci,³ Haiqiang Chen,⁴ and George J. Flick²

U.S. Department of Agriculture, Agricultural Research Service, Microbial Food Safety Research Unit, James W. W. Baker Center, Delaware State University, Dover, Delaware 19901,¹ Department of Food Science and Technology, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061,² U.S. Food and Drug Administration, Gulf Coast Seafood Laboratory, Dauphin Island, Alabama 36528,³ Department of Animal & Food Sciences, University of Delaware, Newark, Delaware 19716-2150⁴

Received 8 September 2006/ Accepted 12 November 2006

Top Abstract Introduction Materials and Methods Results Discussion References

 
Murine norovirus (strain MNV-1), a propagable norovirus, was evaluated for susceptibility to high-pressure processing. Experiments with virus stocks in Dulbecco's modified Eagle medium demonstrated that at room temperature (20°C) the virus was inactivated over a pressure range of 350 to 450 MPa, with a 5-min, 450-MPa treatment being sufficient to inactivate 6.85 log₁₀ PFU of MNV-1. The inactivation of MNV-1 was enhanced when pressure was applied at an initial temperature of 5°C; a 5-min pressure treatment of 350 MPa at 30°C inactivated 1.15 log₁₀ PFU of virus, while the same treatment at 5°C resulted in a reduction of 5.56 log₁₀ PFU. Evaluation of virus inactivation as a function of treatment times ranging from 0 to 150 s and 0 to 900 s at 5°C and 20°C, respectively, indicated that a decreasing rate of inactivation with time was consistent with Weibull or log-logistic inactivation kinetics. The inactivation of MNV-1 directly within oyster tissues was demonstrated; a 5-min, 400-MPa treatment at 5°C was sufficient to inactivate 4.05 log₁₀ PFU. This work is the first demonstration that norovirus can be inactivated by high pressure and suggests good prospects for inactivation of nonpropagable human norovirus strains in foods.

Top Abstract Introduction Materials and Methods Results Discussion References

 
Norovirus infection is a common worldwide problem, with approximately 40% of infections in the United States being food borne (30). Foods most frequently associated with norovirus outbreaks are shellfish and produce, since these foods are often consumed uncooked. The scientific literature is replete with food-borne norovirus outbreaks attributed to these foods (10, 23, 30, 34). Uncooked foods can become contaminated after exposure to contaminated irrigation or propagation waters or, in the case of produce, after human handling.

Research with human norovirus strains has been hampered by the lack of suitable laboratory animals and the inability to propagate the virus in vitro (15). Consequently, genetically related viruses, such as feline calicivirus (FCV) (14) and, to a lesser extent, San Miguel sea lion virus 17 (3), have been used as research surrogates for nonpropagable human norovirus strains. Recently, murine norovirus (strain MNV-1), a virus that can be propagated in vitro, has been identified (18, 38). Classified as a genogroup V virus, MNV-1 has more biochemical, pathological, and molecular similarities to human noroviruses than other research surrogates used previously (39).

High-pressure processing (HPP) has emerged as a promising nonthermal technology for pasteurizing food products. The principal advantage of this technology is that foods retain an uncooked character and taste. HPP has particular utility for the molluscan shellfish industry, since it facilitates the shucking process. Moreover, while organoleptic studies do describe some changes in the character of pressure-treated oysters, HPP-treated oysters are well accepted by consumers (13, 17, 28). Furthermore, HPP technology is currently used commercially to eliminate Vibrio bacteria from U.S. Gulf Coast oysters (2, 12).

Beyond cooking, there currently is no adequate intervention for bivalve shellfish contaminated with enteric viruses because these viruses can remain within shellfish for periods beyond a few days (16, 24, 27, 35). Although some nonenveloped viruses are less sensitive or even completely resistant to pressures as high as 600 MPa (19, 22, 37), HPP has shown promise for inactivation of hepatitis A virus (HAV) and norovirus surrogate viruses. Kingsley et al. (23) demonstrated that 5-min room temperature treatments of 275 MPa and 460 MPa were sufficient to inactivate 7 log₁₀ PFU virus stocks of FCV and HAV, respectively. Subsequent studies demonstrated the utility of HPP for the inactivation of HAV within oysters and produce (4, 21). Characterizing inactivation of the norovirus surrogate FCV by HPP as a function of treatment time indicated that while increased treatment time yielded greater inactivation, there was a diminishing increase in inactivation consistent with nonlinear Weibull or log-logistic inactivation kinetics (8). In evaluating HPP inactivation of FCV as a function of treatment temperature, it was noted that the inactivation increased by as much as 3 log₁₀ when treatments were performed at refrigeration temperatures or above 30°C compared to inactivation with treatments performed at room temperature (8).

In this publication, we evaluate HPP inactivation of the norovirus MNV-1. This virus displayed enhanced inactivation when HPP was performed at refrigeration temperatures. Evaluation of HPP inactivation as a function of treatment time indicates a diminishing increase in virus inactivation consistent with Weibull or log-logistic kinetics. Last, we demonstrate that high-pressure treatment can inactivate the virus directly within MNV-1-contaminated oysters (Crassostrea virginica).

Top Abstract Introduction Materials and Methods Results Discussion References

 
Virus and oysters.
Working stocks of MNV-1 were prepared using confluent monolayers of RAW 264.7 mouse monocytes/macrophages (American Type Culture Collection, Manassas, VA) cultured in high-glucose Dulbecco's modified Eagle medium (DMEM) (Gibco-Invitrogen Co., Grand Island, NY) supplemented with 25 mM HEPES buffer, 10% fetal bovine serum (FBS) (Gibco-Invitrogen), 2 mM Gluta-MAX-1 (Gibco-Invitrogen), 100 U of penicillin, and 100 µg/ml of streptomycin sulfate (Gibco-Invitrogen) essentially as described by Wobus et al. (38).

Eastern oysters (Crassostrea virginica) were harvested from an approved area in Mobile Bay, AL. After being culled and sorted, 200 commercial-size oysters were placed into a depuration flume at the U.S. FDA Gulf Coast Seafood Laboratory, Dauphin Island, AL. Oysters were maintained for >2 weeks prior to being transferred to a flume which utilized single-pass UV-treated natural seawater maintained at 21 to 30°C. Salinities ranged from 5 to 28 ppt.

Three days before virus accumulation, 26 oysters were placed in the accumulation tank to acclimate the shellfish to 10°C, as described previously (4). MNV-1 (5.6 x 10⁹ PFU for trials 1 and 2 and 2.12 x 10⁸ PFU for trial 3) was added to 4 liters of sterile reverse-osmosis water and continually mixed at 4°C. Peristaltic pumps were adjusted to give a calculated overall concentration within the accumulation tank of approximately 7,000 PFU/ml for trials 1 and 2 and 660 PFU/ml for trial 3. After 24 h, the oysters were divided into eight groups of three oysters each and shucked into sterile cups. The total weight for each group was approximately 30 g.

High-pressure treatment of oysters and MNV-1.
For temperature and direct-inactivation experiments, 1.5-ml aliquots of MNV-1 in DMEM with 10% FBS were placed in 2- by 3-in. pouches modified from 4- by 6-in., sterile, 3-mm-thick polyethylene Stomacher pouches (Fisher Scientific International, Ontario, Canada), heat sealed (Tilia Foodsaver Vac 540; San Francisco, CA), and then placed in 6- by 8-in., 3-mm-thick nylon/polyethylene vacuum pouches (Prime Source Packaging, Ltd., Spring, TX) and vacuum/heat sealed (model A 300/16; Multivac, Inc., Kansas City, MO). Pouches were then subjected to pressures ranging from 250 MPa to 450 MPa at specified starting temperatures. For MNV-1-contaminated oysters, shucked samples were transferred into 4.5-mm pouches (Kapak Co., Minneapolis, MN) and heat sealed using an Impulse food sealer (American International Electric Co., Whittier, CA) according to the manufacturer's instructions. An over pack 2-mm pouch was sealed over the inner pouch. Refrigerated, shucked oyster samples were packed in accordance with International Air Transport Association (IATA) dangerous-goods shipping regulations in a biohazard shipping container (STP 100; SAF-T-PAK, Alberta, Canada) and enclosed in an insulated carton with "blue ice" packs to ensure that the temperature remained at <10°C during shipping. Shipments were sent by overnight carrier to the Food Science and Technology Department, Virginia Polytechnic Institute and State University, Blacksburg, VA, for processing. Pressurization of oyster samples was performed for 5 min using a Quintus 35-L food press (QFP 35L-600; Flow International Corporation, Avure Technologies Inc., Kent, WA). Samples were pressurized at 300, 325, 350, 375, and 400 MPa for 5 min at 5°C. The times to reach final pressures were approximately 75 s to achieve 300 MPa and 90 s to achieve 400 MPa. Pressure release time was <3 s. Adiabatic heating during pressurization ranged from 10°C at 300 MPa to 13°C at 400 MPa. After processing, the refrigerated samples were shipped overnight to the USDA Microbial Food Safety Research Unit at Dover, DE, for virus extraction and assay.

Virus extraction and plaque assays.
For MNV-1 stock virus in DMEM, all samples were assayed using confluent six-well dishes (Fisher Biotech, Fairlawn, NJ). Inoculation with 0.5 ml of MNV-1 was carried out for 2 h at 37°C followed by overlay with 2 ml of modified Eagle medium (Gibco-Invitrogen) containing 1.5% low-melting-point agarose (Fisher Biotech) with 5% FBS, 2 mM Gluta-MAX-1, 100 U of penicillin, and 100 µg/ml of streptomycin sulfate (Gibco-Invitrogen). After 3 days of incubation, plaques were visualized by staining with 0.03% neutral red (Fisher Biotech) for 2 h at 37°C.

For MNV-1 extraction from contaminated oysters and plaque assay, three shellfish per treatment group were removed from pressurized sealed pouches, placed in 50-ml conical tubes, and briefly centrifuged in a tabletop centrifuge to facilitate separation of oyster meat from oyster liquor. Nonpressurized (0 MPa), MNV-1-contaminated (positive) controls were also tested. Virus extractions were performed essentially as described by Calci et al. (4) by adding oyster meats (three oysters per treatment group) and phosphate buffer (0.15 M Na₃PO₄, pH 9.5, 4°C) up to 100 ml and homogenizing oyster meats in a laboratory blender (Waring Inc., New Hartford, CT) for 3 min at maximum speed. Homogenized extracts were centrifuged for 15 min at 15,000 x g, and the supernatant was neutralized with 2 N HCl. Tenfold serial dilutions were made in Earle's balanced salt solution (Gibco-Invitrogen), and plaque assays were performed in triplicate using confluent monolayers of RAW cells (38). For undiluted and 1:10-diluted oyster homogenates, 2 ml of extract or 2 ml of dilution was used to infect 100-mm confluent tissue culture dishes. Due to oyster debris remaining in the oyster homogenates, the 100-mm dishes were washed with 2 ml of Earle's balanced salt solution after inoculation and incubation for 2 h. For homogenate dilutions of 1:100 or greater, 0.5 ml was used to infect individual wells of a six-well dish and washing was not performed. Plaques were visualized using neutral red staining 3 days postinfection.

Modeling of survival curves.
The linear model assumes that all cells or spores in a population have the same resistance to lethal treatments and that their inactivation is governed by first-order kinetics (36). The linear model is , where N₀ equals the initial amount of virus (PFU/ml), N equals the number of survivors after an exposure time t (PFU/ml), D (decimal reduction time) equals the time (min) required to destroy 90% of the virus and is a measure of the resistance of a virus to lethal treatments, and t equals the treatment time (min).

The Weibull model assumes that cells and spores in a population have different resistances and that a survival curve is just the cumulative form of a distribution of lethal agents. The Weibull model is , where b and n are the scale and shape factors (33). The Weibull distribution corresponds to a concave upward survival curve if n is <1, concave downward if n is >1, and linear if n equals 1.

The log-logistic model was originally proposed by Cole et al. (11) and later was modified by Chen and Hoover (6) to avoid the use of different initial numbers and to reduce the number of parameters in the equation from four to three. The log-logistic model is log(N/N₀) = {A/[1 + e^{4( – log t)/A}]} – {A/[1 + e^{4( + 6)/A}]}, where A equals upper asymptote – lower asymptote (log₁₀ PFU/ml), equals the maximum rate of inactivation [(log₁₀ PFU/ml)/log₁₀ min], and equals the log₁₀ time to the maximum rate of inactivation (log₁₀ min).

The mean square error (MSE) values were used to compare the three models. The smaller the MSE values, the better the model fit to the data (31). , where n is the number of observations and p is the number of parameters to be estimated.

Survival curves were fitted using the PROC REG procedure of SAS (release 9.1; SAS Institute Inc., Cary, NC) for the linear model and the PROG NLIN procedure of SAS for the nonlinear models.

Top Abstract Introduction Materials and Methods Results Discussion References

 
The effect of high pressure on 1.5-ml aliquots of MNV-1 in DMEM tissue culture media was evaluated using 5-min treatments at 20°C. A logarithmic reduction in virus titer was observed from 325 MPa through 450 MPa (Fig. 1). To evaluate the effect of temperature on virus inactivation, 5-min, 350-MPa pressure treatments of virus stocks were performed at 5, 10, 20, and 30°C (Table 1). Results indicated that a starting temperature of 5°C, when pressure was applied, gave the greatest degree of inactivation, reducing the virus titer by 5.56 log₁₀, while warmer temperatures of 20 and 30°C gave appreciably less inactivation of 1.79 and 1.15 log₁₀, respectively.

View larger version (7K): [in this window] [in a new window]

FIG. 1. Effect of pressure treatment of murine norovirus. Virus samples in DMEM with 10% FBS were treated for 5 min at 20°C. Data are the means of three replicates. Error bars represent standard errors.

View this table: [in this window] [in a new window]

TABLE 1. Five-minute treatments at 350 MPa of MNV-1 stock in DMEM with 10% FBS at different initial temperatures

Inactivation of MNV-1 was also evaluated as a function of pressure level and treatment time (Fig. 2). To characterize high-pressure treatments as a function of time, time course analyses were performed on virus stocks. Since there was considerable disparity in the responses to pressure as a function of temperature, analyses with pressures of 375 MPa at 20°C and 325 MPa at 5°C were performed. As pressure magnitudes and/or treatment times increased, virus inactivation also increased. The shapes of the inactivation curves were characterized by a rapid initial drop in viral counts followed by tailing caused by a diminishing inactivation rate. Visual inspection of these survival curves indicated that a nonlinear model would describe these data better than a linear model. Fitting the survival data with the linear and nonlinear models (Fig. 2) and comparing the goodness-of-fit levels of the models using MSE values confirmed this observation. Among the three models compared, the log-logistic model had the lowest MSE values, indicating that it produced the best fit to the inactivation curves. The linear model produced the poorest fit. The mean MSE values for the linear, Weibull, and log-logistic models were 1.76, 0.16, and 0.14, respectively (Table 2). The greater rate of inactivation observed at the lower temperature (5°C) and pressure (325 MPa) than at the higher temperature (20°C) and pressure (375 MPa) reinforces the finding that cooler temperatures result in substantially greater inactivation of MNV-1.

View larger version (17K): [in this window] [in a new window]

FIG. 2. Inactivation curves of murine norovirus. Time course analysis of pressure treatment of MNV-1 stock virus was performed at 325 MPa and 5°C and at 375 MPa and 20°C. Data are the means of three replicates and were fitted with linear, Weibull, and log-logistic functions. Error bars represent ±1 standard error. Pressurization time did not include the times to achieve final pressures or release times.

View this table: [in this window] [in a new window]

TABLE 2. Comparison of goodness-of-fit levels of the linear, Weibull, and log-logistic models

To demonstrate that high-pressure treatment could inactivate MNV-1 within shellfish tissues, live oysters (C. virginica) were exposed for 24 h to high levels of MNV-1 in seawater to mimic environmental accumulation of enteric virus in shellfish-growing waters. Three different accumulation assays using three oysters per experiment were performed. Extraction of MNV-1 from each untreated group of three oysters yielded 1.47 x 10⁵, 2.7 x 10⁵, and 1.8 x 10⁴ PFU, respectively, confirming that MNV-1 was accumulated to high levels after exposure. For 5-min, 5°C HPP treatments of MNV-contaminated oysters, onset of inactivation was observed at 325 MPa, with a 400-MPa treatment being sufficient to inactivate 4.05 log₁₀ PFU (Fig. 3).

View larger version (7K): [in this window] [in a new window]

FIG. 3. Effect of pressure treatments on MNV-contaminated oysters. MNV-contaminated oysters were administered 5-min treatments at 5°C. Average reductions in extractable MNV-1 are displayed graphically as logarithmic reductions from three trials. Error bars represent standard errors for titer reductions from three trials.

Top Abstract Introduction Materials and Methods Results Discussion References

 
This is the first direct demonstration that a norovirus, rather than a norovirus surrogate, can be inactivated by high pressure. This demonstration suggests good prospects for inactivation of human norovirus strains by high pressure but should also be viewed with caution, since different viruses and even different strains of viruses can differ in susceptibility to HPP (19). It should be noted that murine norovirus was less sensitive to pressure than the norovirus surrogates FCV or San Miguel sea lion virus 17, which were reduced by >7 log₁₀ PFU/ml after a 5-min, 300-MPa treatment and >2.49 log₁₀ PFU/ml after a 1-min, 300-MPa treatment at 10°C, respectively (3, 22).

Given that FCV inactivation is enhanced by cooler temperatures of <20°C (8), it is not entirely surprising that HPP inactivation of MNV-1, also a calicivirus, is enhanced by cooler temperatures. Cooler temperatures may maximize the protein denaturation under pressure due to increased density of water molecules in the protein solvation cage (1, 26). This temperature effect is not restricted to the caliciviruses, since the picornavirus foot-and-mouth disease virus has also been shown to have enhanced inactivation at cooler temperatures (32). It should be noted that HAV, another picornavirus, is an exception to this general rule, since cooler temperatures do not enhance HAV inactivation (20).

Treatment time inactivation curves at both 5°C and 20°C were consistent with log-logistic and Weibull kinetics rather than linear first-order kinetics. Nonlinear inactivation curves as a function of constant pressure and time have been observed previously for other viruses, such as FCV and HAV (8, 20), as well as for bacteriophage (9) and a host of bacterial species (6, 7). Our observation is consistent with curves obtained for other microorganisms and may be a general property of high-pressure inactivation.

For oysters, results indicate that MNV-1 inactivation is feasible at 400 MPa, with 400 MPa being the probable upper limit for commercial HPP treatment. Since greater inactivation was observed for stock virus at 5°C than at 20°C, treatment of oysters was performed at the cooler temperature. It was important to perform studies with contaminated oysters since virus inactivation by HPP is influenced by the environment in which the virus is found. How viruses sequester themselves within shellfish meats is not well understood. Conceivably, MNV-1 could be sequestered in a number of different anatomical structures within the oyster, including within mucous membranes, within digestive gland contents, within phagocytic cells, or free floating within the open circulatory system of the oyster. For oysters, it is conceivable that physiologic, environmental, and seasonal factors, such as water salinity, may also alter HPP effectiveness. Shellfish are osmoconformers, meaning their internal ionic strength mimics the ionic strength of the waters in which they reside. Oysters used in this study were harvested from Mobile Bay, AL, an estuary with salinity ranging from 5 to 28 ppt. These oysters were harvested in late winter to early spring prior to spawning.

If human and murine noroviruses have similar susceptibilities to high pressure, we believe that HPP could be a viable processing intervention, particularly if pressure treatment could be performed at refrigeration temperatures. It is generally accepted that less than 100 virions are sufficient to initiate illness (10). While shellfish can accumulate norovirus to high levels, as demonstrated in this study, it is probable that shellfish legally harvested from approved growing areas would not be grossly contaminated. Presumably, a 4-log₁₀ reduction in PFU would correlate with a similar reduction in infectious doses present within contaminated shellfish. It is important to note that cooking has not always been sufficient to prevent shellfish-borne virus transmission (5, 25, 29). Consequently, high pressure may also prove useful for reducing infectious virus in bivalves prior to cooking.

In summary, this study demonstrates that MNV-1 can be inactivated readily by high pressure, which may be a practical intervention for foods potentially contaminated with noroviruses, such as shellfish. This inactivation is enhanced at temperatures below 20°C. HPP inactivation of MNV-1 as a function of time reveals inactivation kinetics consistent with Weibull and log-logistic kinetics. Inactivation of MNV-1 directly within oysters was also demonstrated.

 
We thank Gloria Meade (USDA, Dover, DE) for technical support, Gary P. Richards (USDA, Dover, DE) and John Luchansky (USDA, Wyndmoor, PA) for critical reading of the manuscript, and John Phillips (USDA, Wyndmoor, PA) for assistance with statistical analysis.

This work was funded in part by USDA CSREES grant no. 2005-51110-03271.

Mention of trade names or commercial products in this article is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the U.S. Department of Agriculture.

 
* Corresponding author. Mailing address: U.S. Department of Agriculture, Agricultural Research Service, Microbial Food Safety Research Unit, James W. W. Baker Center, Delaware State University, Dover, DE 19901. Phone: (302) 857-6406. Fax: (302) 857-6451. E-mail: dkingsle{at}desu.edu.

Published ahead of print on 1 December 2006.

Top Abstract Introduction Materials and Methods Results Discussion References

 

1
1. Balny, C., P. Masson, and K. Heremans. 2002. High pressure effects on biological macromolecules: from structural changes to alteration of cellular processes. Biochim. Biophys. Acta Protein Struct. Mol. Enzymol. 1595:3-10.
2
2. Berlin, D. L., D. S. Herson, D. T. Hicks, and D. G. Hoover. 1999. Response of pathogenic Vibrio species to high hydrostatic pressure. Appl. Environ. Microbiol. 65:2776-2780.[Abstract/Free Full Text]
3
3. Calci, K. R., W. Burkhardt III, and A. V. Smith. 2002. High hydrostatic pressure inactivation of calicivirus (SMSV-17) in oysters, abstr. P224. Int. Assoc. Food Prot. Annu. Meet., San Diego, CA, 30 June to 3 July 2002.
4
4. Calci, K. R., G. K. Meade, R. C. Tezloff, and D. H. Kingsley. 2005. High-pressure inactivation of hepatitis A virus within oysters. Appl. Environ. Microbiol. 71:339-343.[Abstract/Free Full Text]
5
5. Chalmers, J. W., and J. H. McMillan. 1995. An outbreak of viral gastroenteritis associated with adequately prepared oysters. Epidemiol. Infect. 115:163-167.[Medline]
6
6. Chen, H., and D. G. Hoover. 2003. Pressure inactivation kinetics of Yersinia enterocolitica ATCC 35669. Int. J. Food Microbiol. 87:161-171.[CrossRef][Medline]
7
7. Chen, H., and D. G. Hoover. 2004. Use of the Weibull model to describe and predict pressure inactivation of Listeria monocytogenes Scott A in whole milk. Innov. Food Sci. Emerg. Technol. 5:269-276.[CrossRef]
8
8. Chen, H., D. G. Hoover, and D. H. Kingsley. 2005. Temperature and treatment time influence high hydrostatic pressure inactivation of feline calicivirus, a norovirus surrogate. J. Food Prot. 68:2389-2394.[Medline]
9
9. Chen, H., R. D. Joerger, D. H. Kingsley, and D. G. Hoover. 2004. Pressure inactivation kinetics of phage cI 857. J. Food Prot. 67:505-511.[Medline]
10
10. Cliver, D. O. 1997. Virus transmission via food. Food Technol. 51:71-78.
11
11. Cole, M. B., K. W. Davies, G. Munro, C. D. Holyoak, and D. C. Kilsby. 1993. A vitalistic model to describe the thermal inactivation of Listeria monocytogenes. J. Ind. Microbiol. 12:232-239.[CrossRef]
12
12. Cook, D. W. 2003. Sensitivity of Vibrio species in phosphate-buffered saline and in oysters to high-pressure processing. J. Food Prot. 66:2276-2282.[Medline]
13
13. Cruz-Romero, M., M. Smiddy, C. Hill, J. P. Kerry, and A. L. Kelly. 2004. Effects of high pressure treatment on physiochemical characteristics of fresh oysters (Crassostrea gigas). Innov. Food Sci. Emerg. Technol. 5:161-169.[CrossRef]
14
14. Doultree, J. C., J. D. Druce, C. J. Birch, D. S. Bowden, and J. A. Marshall. 1999. Inactivation of feline calicivirus, a Norwalk virus surrogate. J. Hosp. Infect. 41:51-57.[CrossRef][Medline]
15
15. Duizer, E., K. J. Schwab, F. H. Neill, R. L. Atmar, M. P. G. Koopmans, and M. K. Estes. 2004. Laboratory efforts to cultivate noroviruses. J. Gen. Virol. 85:79-87.[Abstract/Free Full Text]
16
16. Grohmann, G. S., A. M. Murphy, P. J. Christopher, E. Auty, and H. B. Greenberg. 1981. Norwalk virus gastroenteritis in volunteers consuming depurated oysters. Aust. J. Exp. Biol. Med. Sci. 59:219-228.[Medline]
17
17. He, H., R. M. Adams, D. F. Farkas, and M. T. Morrissey. 2002. Use of high-pressure processing for oyster shucking and shelf-life extension. J. Food Sci. 67:640-645.[CrossRef]
18
18. Karst, S. M., C. E. Wobus, M. Lay, J. Davidson, and H. W. Virgin IV. 2003. STAT 1-dependent innate immunity to a Norwalk-like virus. Science 299:1575-1578.[Abstract/Free Full Text]
19
19. Kingsley, D. H., H. Chen, and D. Hoover. 2004. Inactivation of selected picornaviruses by high hydrostatic pressure. Virus Res. 102:221-224.[CrossRef][Medline]
20
20. Kingsley, D. H., D. Guan, D. G. Hoover, and H. Chen. 2006. Inactivation of hepatitis A virus by high pressure processing: the role of temperature and pressure oscillation. J. Food Prot. 69:2454-2459.
21
21. Kingsley, D. H., D. Guan, and D. G. Hoover. 2005. Pressure inactivation of hepatitis A virus in strawberry puree and sliced green onions. J. Food Prot. 68:1748-1751.
22
22. Kingsley, D. H., D. Hoover, E. Papafragkou, and G. P. Richards. 2002. Inactivation of hepatitis A virus and a calicivirus by high hydrostatic pressure. J. Food Prot. 65:1605-1609.[Medline]
23
23. Kingsley, D. H., G. K. Meade, and G. P. Richards. 2002. Detection of both hepatitis A virus and Norwalk-like virus in imported clams associated with food-borne illness. Appl. Environ. Microbiol. 68:3914-3918.[Abstract/Free Full Text]
24
24. Kingsley, D. H., and G. P. Richards. 2003. Persistence of hepatitis A virus within oysters. J. Food Prot. 66:331-334.[Medline]
25
25. Kirkland, K. B., R. A. Meriwether, J. K. Leiss, and W. R. MacKenzie. 1996. Steaming oysters does not prevent Norwalk-like gastroenteritis. Public Health Rep. 111:527-530.
26
26. Kunugi, S., and N. Tanaka. 2002. Cold denaturation of proteins under high pressure. Biochim. Biophys. Acta Protein Struct. Mol. Enzymol. 1595:329-344.
27
27. LeGuyader, F. S., F. Loisy, R. L. Atmar, A. E. Hutson, M. K. Estes, N. Ruvoen-Clouet, M. Pommepuy, and J. Le Pendu. 2006. Norwalk virus-specific binding to oyster digestive tissues. Emerg. Infect. Dis. 12:931-936.[Medline]
28
28. Lopez-Caballero, M. E., M. Perez-Mateos, P. Montero, and A. J. Borderias. 2000. Oyster preservation by high-pressure treatment. J. Food Prot. 63:196-201.[Medline]
29
29. McDonnell, S., K. B. Kirkland, W. G. Hlady, C. Aristeguieta, R. S. Hopkins, S. S. Monroe, and R. I. Glass. 1997. Failure of cooking to prevent shellfish associated gastroenteritis. Arch. Intern. Med. 157:111-116.[Abstract/Free Full Text]
30
30. Mead, P. S., L. Slutsker, V. Dietz, L. F. McCaig, J. S. Bresee, C. Shapiro, P. M. Griffin, and R. V. Tauxe. 1999. Food-related illness and death in the United States. Emerg. Infect. Dis. 5:607-625.[Medline]
31
31. Neter, J., M. H. Kutner, C. J. Nachtsheim, and W. Wasserman. 1996. Applied linear regression models. McGraw-Hill Co., Inc., Chicago, IL.
32
32. Oliveira, A. C., D. Ishimaru, R. B. Goncalves, P. Mason, D. Carvalho, T. Smith, and J. L. Silva. 1999. Low temperature and pressure stability of picornaviruses: implication for virus uncoating. Biophys. J. 76:1270-1279.
33
33. Peleg, M., and M. B. Cole. 1998. Reinterpretation of microbial survival curves. Crit. Rev. Food Sci. Nutr. 38:353-380.[CrossRef][Medline]
34
34. Potasman, I., A. Paz, and M. Odeh. 2002. Infectious outbreaks associated with bivalve shellfish consumption: a worldwide perspective. Clin. Infect. Dis. 35:921-928.[CrossRef][Medline]
35
35. Power, U. F., and J. K. Collins. 1989. Differential depuration of poliovirus, Escherichia coli, and coliphage by the common mussel, Mytilus edulis. Appl. Environ. Microbiol. 55:1386-1390.[Abstract/Free Full Text]
36
36. Schaffner, D. W., and T. P. Labuza. 1997. Predictive microbiology: where are we, and where are we going? Food Technol. 51:95-99.
37
37. Wilkinson, N., A. S. Kurdziel, S. Langton, E. Needs, and N. Cook. 2001. Resistance of poliovirus to inactivation by high hydrostatic pressure. Innov. Food Sci. Emerg. Technol. 2:95-98.[CrossRef]
38
38. Wobus, C. E., S. M. Karst, L. B. Thackray, K.-O. Chang, S. V. Sosnovtsev, G. Belliot, A. Krug, J. M. Mackenzie, K. Y. Green, and H. W. Virgin IV. 2004. Replication of norovirus in cell culture reveals a tropism for dendritic cells and macrophages. PLoS Biol. 2:2076-2084.
39
39. Wobus, C. E., L. B. Thackray, and H. W. Virgin IV. 2006. Murine norovirus: a model system to study norovirus biology and pathogenesis. J. Virol. 80:5104-5112.[Free Full Text]

---

Applied and Environmental Microbiology, January 2007, p. 581-585, Vol. 73, No. 2
0099-2240/07/$08.00+0     doi:10.1128/AEM.02117-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

This article has been cited by other articles:

• Buckow, R., Isbarn, S., Knorr, D., Heinz, V., Lehmacher, A. (2008). Predictive Model for Inactivation of Feline Calicivirus, a Norovirus Surrogate, by Heat and High Hydrostatic Pressure. Appl. Environ. Microbiol. 74: 1030-1038 [Abstract] [Full Text]  

This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Reprints and Permissions Copyright Information Books from ASM Press MicrobeWorld Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Kingsley, D. H. Articles by Flick, G. J. Search for Related Content PubMed PubMed Citation Articles by Kingsley, D. H. Articles by Flick, G. J. Agricola Articles by Kingsley, D. H. Articles by Flick, G. J.