Detection of GII.4 norovirus sequences in animal fecal samples and retail meats demonstrates that noroviruses may be transmitted zoonotically.

Enterobacter sakazakii has been implicated as the causal organism in a severe form of neonatal meningitis, with reported mortality rates of 40 to 80%. Dried infant formula has been identified as a potential source of the organism in both outbreaks and sporadic cases. In this study, clinical and foodborne isolates of E. sakazakii were evaluated for enterotoxin production by the suckling mouse assay. In addition, suckling mice were challenged both orally and by intraperitoneal injection. Of 18 E. sakazakii strains evaluated, four were found to test positive for enterotoxin production. All strains of E. sakazakii were lethal to suckling mice at 10(8) CFU per mouse by intraperitoneal injection, while two strains caused death by the peroral route. In in vitro assays, CHO, Vero, and Y-1 cells demonstrated both cell lysis and rounding when exposed to E. sakazakii strain LA filtrates. This is the first report describing any putative virulence factors of E. sakazakii.

Hepatitis A virus (HAV) is an important pathogen which has been responsible for many food-borne outbreaks. HAV-excreting food handlers, especially those with poor hygienic practices, can contaminate the foods which they handle. Consumption of such foods without further processing has been known to result in cases of infectious hepatitis. Since quantitative data on virus transfer during contact of hands with foods is not available, we investigated the transfer of HAV from artificially contaminated fingerpads of adult volunteers to pieces of fresh lettuce. Touching the lettuce with artificially contaminated fingerpads for 10 s at a pressure of 0.2 to 0.4 kg/cm 2 resulted in transfer of 9.2% ؎ 0.9% of the infectious virus. The pretreatments tested to interrupt virus transfer from contaminated fingerpads included (i) hard-water rinsing and towel drying, (ii) application of a domestic or commercial topical agent followed by water rinsing and towel drying, and (iii) exposure to a hand gel containing 62% ethanol or 75% liquid ethanol without water rinsing or towel drying. When the fingerpads were treated with the topical agents or alcohol before the lettuce was touched, the amount of infectious virus transferred to lettuce was reduced from 9.2% to between 0.3 and 0.6% (depending on the topical agent used), which was a reduction in virus transfer of up to 30-fold. Surprisingly, no virus transfer to lettuce was detected when the fingerpads were rinsed with water alone before the lettuce was touched. However, additional experiments with water rinsing in which smaller volumes of water were used (1 ml instead of 15 ml) showed that the rate of virus transfer to lettuce was 0.3% ؎ 0.1%. The variability in virus transfer rates following water rinsing may indicate that the volume of water at least in part influences virus removal from the fingerpads differently, a possibility which should be investigated further. This study provided novel information concerning the rate of virus transfer to foods and a model for investigating the transfer of viral and other food-borne pathogens from contaminated hands to foods, as well as techniques for interrupting such transfer to improve food safety.Hepatitis A is a common form of acute viral hepatitis in many parts of the world. It is responsible for significant worldwide morbidity and occasional mortality (21, 27). Outbreaks of hepatitis A occur periodically throughout the world, and fecally contaminated food and water are the main vehicles (4). Although less than 10% of the cases of hepatitis A in the United States are associated with food-borne outbreaks (7), substantial costs are incurred by both society and the food industry as a result of these outbreaks (11). The foods implicated in these outbreaks include shellfish (13,14,18,22,28,31), sandwiches, dairy products, baked products, salads, fruits, and vegetables (9, 15). Examples of such outbreaks include the outbreak in Denver, Color., in 1992, in which more than 5,000 individuals were exposed to hepatitis A virus (HAV) due to consump...

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While there is good epidemiological evidence for foods as vehicles for norovirus transmission, the precise means of spread and its control remain unknown. The feline calicivirus was used as a surrogate for noroviruses to study infectious virus transfer between hands and selected types of foods and environmental surfaces. Assessment of the potential of selected topicals in interrupting such virus transfer was also made. Ten microliters of inoculum of feline calicivirus deposited onto each fingerpad of adult subjects was allowed to air dry and the contaminated area on individual fingerpads was pressed (10 s at a pressure of 0.2 to 0.4 kg/cm2) onto 1-cm-diameter disks of ham, lettuce, or brushed stainless steel. The virus remaining on the donor and that transferred to the recipient surfaces was eluted and plaque assayed. Virus transfer to clean hands from experimentally contaminated disks of ham, lettuce, and stainless steel was also tested. Nearly 46 +/- 20.3, 18 +/- 5.7, and 13 +/- 3.6% of infectious virus was transferred from contaminated fingerpads to ham, lettuce, and metal disks, respectively. In contrast, approximately 6 +/- 1.8, 14 +/- 3.5, and 7 +/- 1.9% virus transfer occurred, respectively, from ham, lettuce, and metal disks to hands. One-way analysis of variance test showed that pretreatment (washing) of the fingerpads either with water or with both topical agent and water significantly (P < 0.05) reduced virus transfer to < or = 0.9%, as compared with < or = 2.3 and < or = 3.4% transfer following treatments with either 75% (vol/vol) ethanol or a commercial hand gel containing 62% ethanol, respectively. Despite wide variations in virus transfer among the targeted items used, intervention agents tested reduced virus transfer significantly (P < 0.05) when compared with that without such treatments (71 +/- 8.9%). These findings should help in a better assessment of the potential for cross-contamination of foods during handling and also assist in developing more effective approaches to foodborne spread of norovirus infections.

Although there is a large body of evidence incriminating foods as vehicles in the transmission of norovirus, little is known about virus survival in foods and on surfaces. Feline calicivirus was used as a surrogate for norovirus to investigate its survival in representative foods of plant and animal origin and on metal surfaces. Known concentrations of feline calicivirus in a natural fecal suspension were deposited onto lettuce, strawberries, ham, or stainless steel and incubated for 7 days at refrigeration or room temperatures. Virus was recovered at 1-day intervals, and the titers of the virus were determined by plaque assay. Infectious virus was recoverable until day 7 from lettuce, ham, and stainless steel. Statistically higher titers of feline calicivirus (P < 0.05) were recovered from ham under all conditions than from lettuce, strawberries, or stainless steel. These data provide valuable information for epidemiological and monitoring purposes as well as for the development of food processing practices and appropriate strategies to inactivate norovirus and control its transmission via foods and surfaces.

Experiments were performed to determine the thermal resistance of hepatitis A virus (HAV) in three types of dairy products containing increased amounts of fat content (skim milk, homogenized milk; 3.5% MFG, and table cream; 18% MFG). HAV-inoculated dairy products were introduced into custom-made U-shaped microcapillary tubes that in turn were simultaneously immersed in a waterbath, using custom-made floating boats and a carrying platform. Following exposure to the desired time and temperature combinations, the contents of each of the tubes was retrieved and was tested by plaque assay to determine the reduction in virus titer. Our data indicated that Ͻ0.5 min at 85ЊC was sufficient to cause a 5-log reduction in HAV titer in all three dairy products, whereas at 80ЊC, Յ0.68 min (for skim and homogenized milk), and 1.24 min (for cream) were needed to cause a similar log reduction. Using a nonlinear two-phase negative exponential model (two-compartment model) to analyze the data, it was found that at temperatures of 65, 67, 69, 71, and 75ЊC, significantly (P Ͻ 0.05) higher exposure times were needed to achieve a 1-log reduction in virus titer in cream, as compared to skim and homogenized milk. For example, at 71ЊC, a significantly (P Ͻ 0.05) higher exposure time of 0.52 min (for cream) was needed as compared to Յ0.18 min (for skim and homogenized milk) to achieve a 1-log reduction in virus titer. A similar trend of inactivation was observed at 73 and 75ЊC where significantly (P Ͻ 0.05) higher exposure times of 0.29 to 0.36 min for cream were needed to cause a 1-log reduction in HAV in cream, as compared to Յ0.17 min for skim and homogenized milk. This study has provided information on the heat resistance of HAV in skim milk, homogenized milk, and table cream and demonstrated that an increase in fat content appears to play a protective role and contributes to the heat stability of HAV.Hepatitis A virus (HAV), the causative agent of hepatitis A, is a member of the Picornaviridae family. Because of its unique genetic and physical characteristics, HAV has now been assigned to a distinct genus, hepatovirus (17). It is a 27-nm icosahedral, nonenveloped virus, containing a 7.5-kb positive-stranded RNA genome that is enclosed by a capsid protein shell consisting of VP1, VP2, VP3, and VP4 glycoproteins. Despite its successful propagation in cell culture (3,19), wild-type HAV strains are still very difficult to culture, even in primary mammalian cells. Although similar to other enteroviruses in morphology and composition, HAV exhibits greater resistance to inactivation by various chemical and physical agents, including heat (4,6,8,21). Outbreaks of foodborne hepatitis have been well documented epidemiologically with a wide variety of foods, such as shellfish, salads, fruits, and dairy products being implicated (1,2,20). Most investigations have focused on the use of heat as a method of inactivating HAV in shellfish. Koff and Sear (10) indicated that it took 4 to 6 min for the internal temperature to reach 100ЊC in st...

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