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Foodborne viruses, particularly human norovirus, are a concern for public health, especially in fresh vegetables and other minimally processed foods that may not undergo sufficient decontamination. It is necessary to explore novel nonthermal techniques for preventing foodborne viral contamination. In this study, aqueous extracts of six raw food materials (flower buds of clove, fenugreek seeds, garlic and onion bulbs, ginger rhizomes, and jalapeño peppers) were tested for antiviral activity against feline calicivirus (FCV) as a surrogate for human norovirus. The antiviral assay was performed using dilutions of the extracts below the maximum nontoxic concentrations of the extracts to the host cells of FCV, Crandell-Reese feline kidney (CRFK) cells. No antiviral effect was seen when the host cells were pretreated with any of the extracts. However, pretreatment of FCV with nondiluted clove and ginger extracts inactivated 6.0 and 2.7 log of the initial titer of the virus, respectively. Also, significant dosedependent inactivation of FCV was seen when host cells were treated with clove and ginger extracts at the time of infection or postinfection at concentrations equal to or lower than the maximum nontoxic concentrations. By comprehensive two-dimensional gas chromatography-mass spectrometry analysis, eugenol (29.5%) and R-(-)-1,2-propanediol (10.7%) were identified as the major components of clove and ginger extracts, respectively. The antiviral effect of the pure eugenol itself was tested; it showed antiviral activity similar to that of clove extract, albeit at a lower level, which indicates that some other clove extract constituents, along with eugenol, are responsible for inactivation of FCV. These results showed that the aqueous extracts of clove and ginger hold promise for prevention of foodborne viral contamination.

Forty samples of fresh produce collected from retail food establishments were examined to determine the occurrence of Escherichia coli, F-specific coliphages, and noroviruses. An additional six samples were collected from a restaurant undergoing investigation for a norovirus outbreak. Nineteen (48%) of the retail samples and all outbreak samples were preprocessed (cut, shredded, chopped, or peeled) at or before the point of purchase. Reverse transcription-PCR, with the use of primers JV 12 and JV 13, failed to detect norovirus RNA in any of the samples. All six outbreak samples and 13 (33%) retail samples were positive for F-specific coliphages (odds ratio undefined, P = 0.003). Processed retail samples appeared more likely to contain F-specific coliphages than unprocessed samples (odds ratio 3.8; 95% confidence interval 0.8 to 20.0). Only two (5.0%) retail samples were positive for E. coli; outbreak samples were not tested for E. coli. The results of this preliminary survey suggest that F-specific coliphages could be useful conservative indicators of fecal contamination of produce and its associated virological risks. Large-scale surveys should be conducted to confirm these findings.

We conducted a series of experiments to compare the survival of Escherichia coli, feline calicivirus, and F-specific coliphage MS2 on lettuce and cabbage with and without disinfection. Inoculated produce was held at 4, 25, or 37 degrees C for 21 days or was treated with different concentrations of sodium bicarbonate, chlorine bleach, peroxyacetic acid, or hydrogen peroxide. Survival was measured by the decimal reduction value (time to 90% reduction in titer) and the change in log titers of the test organisms. A stronger correlation of survival measures was observed between feline calicivirus and MS2 than between E. coli and either of the viral agents at 25 and 37 degrees C. The maximum time to detection limit for MS2 at all temperatures was 9 days, whereas feline calicivirus was detected for a maximum of 14 days at 4 degrees C. In contrast, E. coli was detectable for 21 days at 4 and 25 degrees C and for 14 days at 37 degrees C. Significant increases in E. coli titer occurred within the first 5 days, but virus titers decreased steadily throughout the experiments. E. coli was also highly susceptible to all disinfectants except 1% sodium bicarbonate and 50 ppm chlorine bleach, whereas the viruses were resistant to all four disinfectants.

Outbreaks of human Norwalk virus (NV) and Norwalk-like viruses often originate in food service establishments. No reliable method is available for the detection of these human caliciviruses on food contact surfaces. We describe a simple method for the detection of NV from stainless steel work surfaces using cultivable feline calicivirus (FCV) as a model. Stainless steel surfaces were artificially contaminated with known amounts of FCV, followed by its elution in a buffer solution. Three methods of virus elution were compared. In the first method, moistened cotton swabs or pieces of nylon filter (1MDS) were used to elute the contaminating virus. The second method consisted of flooding the contaminated surface with eluting buffer, allowing it to stay in contact for 15 min, followed by aspiration of the buffer (aspiration method) after a contact period of 15 min. The third method, the scraping-aspiration method, was similar to the aspiration method, except that the surfaces were scraped with a cell scraper before buffer aspiration. Maximum virus recovery (32 to 71%) was obtained with the scraping-aspiration method using 0.05 M glycine buffer at pH 6.5. Two methods (organic flocculation and filter adsorption elution) were compared to reduce the volume of the eluate recovered from larger surfaces. The organic flocculation method gave an average overall recovery of 55% compared to the filter-adsorption-elution method, which yielded an average recovery of only 8%. The newly developed method was validated for the detection of NV by artificial contamination of 929-cm2 stainless steel sheets with NV-positive stool samples and for the detection of the recovered virus by reverse transcription-polymerase chain reaction.

Norwalk and Norwalk-like viruses (NLVs) are important causes of foodborne gastroenteritis in restaurant-related outbreaks. Efficacy of common disinfection methods against these viruses on food-contact surfaces and fresh produce is not known partially because of their nonculturability. Seven commercial disinfectants for food-contact surfaces and three sanitizers for fruits and vegetables were tested against cultivable feline calicivirus (FCV). Disks of stainless steel, strawberry, and lettuce were contaminated with known amounts of FCV. The disinfectants were applied at one, two, and four times the manufacturer's recommended concentrations for contact times of 1 and 10 min. The action of disinfectant was stopped by dilution, and the number of surviving FCVs was determined by titration in cell cultures. An agent was considered effective if it reduced the virus titer by at least 3 log10 from an initial level of 10(7) 50% tissue culture infective dose. None of the disinfectants was effective when used at the manufacturer's recommended concentration for 10 min. Phenolic compounds, when used at two to four times the recommended concentration, completely inactivated FCV on contact surfaces. A combination of quaternary ammonium compound and sodium carbonate was effective on contact surfaces at twice the recommended concentration. Rinsing of produce with water alone reduced virus titer by 2 log10. On artificially contaminated strawberry and lettuce, peroxyacetic acid and hydrogen peroxide was the only effective formulation when used at four times the manufacturers' recommended concentration for 10 min. These findings suggest that FCV and perhaps NLVs are very resistant to commercial disinfectants. However, phenolic compounds at two to four times their recommended concentrations appear to be effective at decontaminating environmental surfaces and may help control foodborne outbreaks of calicivirus in restaurants.

This study concerns the seasonal variation of bacteria in seawater and mussels harvested from a Moroccan coastal area subject to clandestine shellfishing. The changes in the level of bacterial counts of mussels from harvest to sale are also presented. Both seawater and mussels showed regular increases in bacterial loads from fall to summer. Freshly harvested mussels and market mussels were the most contaminated, while freshly shucked mussels, obtained by removing shells after heating shellstock, were the least contaminated. Heating, traditionally used to remove shells, was found to reduce the initial bacterial loads by 72%. However, the storage of shucked mussels for 6 to 8 h at ambient temperatures prior to marketing resulted in an increase in the number of bacteria either due to recontamination or by growth of survivors. Thus, market mussels were 20 to 86 times more contaminated than shellstock and shucked mussels, respectively. No human pathogens were found, but several species of marine vibrios were identified.

Three methods were evaluated for the concentration of poliovirus from artificially contaminated oysters ( Crassostrea gigas ), mussels ( Mytilus edulis ) and carpet-shell clams ( Ruditapes decussatus ) grown in Morocco. The methods tested were: an adsorption-elution-precipitation method, a beef extract elution acid-precipitation method, and a non-fat dry milk elution acid-precipitation method. For all shellfish species tested, the adsorption-elution-precipitation method yielded the lowest average virus recovery (27%), whereas the two elution-precipitation methods yielded average virus recoveries of 42% each. The beef extract elution acid-precipitation method yielded the highest virus recovery with clams (53%), whereas non-fat dry milk elution acid-precipitation was advantageous for mussels providing average virus recovery of 47%. For oysters, none of the tested methods gave satisfactory virus recovery. These results point towards the need for the development of better method(s) for the concentration of viruses from Moroccan oysters, while for mussels and clams, the elution-acid precipitation methods may be satisfactory.

Temperature-sensitive gels (cross-linked, partially hydrolyzed polyacrylamide gels) with the property to absorb solutes less than 1 nm in diameter at 4°C and collapse at higher temperatures (190°C) were used to concentrate Escherichia coli from 2% low-fat milk. Milk samples seeded with bacteria were reduced eight-fold in volume with average recoveries of 40-66% at an optimal pH of 5.5. Repeated use of the gel did not affect its efficiency.

Enteric viruses previously have been reported in marine waters and shellfish which met acceptable bacteriological standards for recreational use and shellfish harvesting. Unfortunately, previous data on occurrence of enteric viruses are limited and usually not quantitative. In this report, results of studies conducted along the upper Texas Gulf coast, where a substantial amount of quantitative virological data was collected, are compared to bacteriological indicators and other environmental factors on a statistical basis. A product-moment correlation matrix showed that there was a moderate correlation between viruses in water and total coliforms in water, total coliforms in oysters and fecal coliforms in oysters. However, presence of viruses in water was not found to be correlated with presence of viruses in oysters. The only significant regression coefficient found for the model relating the concentration of viruses in water to bacterial indicators and other environmental variables was concentration of coliforms in oysters. Multiple regression analysis showed that approximately 25% of the variance in the number of viruses detected in water was statistically accounted for by the linear correlation with the total coliforms in oysters. The amount of variation in the number of viruses explained by this indicator, however, was not large enough to make the concentration of coliforms in oysters a good predictor of the concentration of viruses in water. Furthermore, none of the bacterial or other environmental variables was found to be a good predictor of the concentration of viruses detected in oysters. Our failure to find a strong predictive relationship between viruses in marine water and in oysters, and the occurrence of viruses in high frequency in waters which met current bacteriological standards, indicate that these standards do not reflect the occurrence of enteroviruses in marine waters.

During feeding, bivalve mollusks (oysters, mussels and clams) can accumulate pathogenic human enteric viruses when present in sewage-polluted seawater. It has been well established that infectious hepatitis virus is transmitted by consumption of raw or inadequately cooked shellfish. But because of the lack of epidemiologic techniques, transmission of other enteric viruses by shellfish has not been established. Other enteric viruses, such as polio, echo, coxsackie and reo, have been detected in shellfish. Enteroviruses have been detected in shellfish taken from both "open" and "closed" areas, based on bacteriological standards used at present in the United States. Field and laboratory studies have indicated that enteric viruses can survive for long periods in seawater and in shellfish. Recent advances in methodology have led to development of more rapid and less expensive methods for detection of a greater number of enteric viruses in shellfish.