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Viruses transmitted to humans via foods generally emanate from the human intestines. In the United States, Norwalk virus ranked #5, hepatitis A virus #6, and "other viruses" (principally rotavirus) #10 among the top 10 causes of foodborne disease during 1983-1987. Molluscs are the most frequently reported vehicles, but any food handled by humans may transmit human enteric viruses. Some fruit and vegetable vehicles may have been contaminated in the field before or during harvesting. Viruses in foods may be inactivated before the food is eaten, and thus, not cause infection. Increasingly sensitive detection methods, largely based on "molecular" techniques, are becoming available for these viruses but are not applicable to monitoring foods on a routine basis.

The microbiology of Plastic and wooden cutting boards was studied, regarding cross-contamination of foods in home kitchens. New and used Plastic (four polymers plus hard rubber) and wood (nine hardwoods) cutting boards were cut into 5-cm squares ("blocks"). Escherichia coli (two nonpathogenic strains plus type O157:H7), Listeria innocua , L. monocytogenes , or Salmonella typhimurium was applied to the 25-cm2 block surface in nutrient broth or chicken juice and recovered by soaking the surface in nutrient broth or pressing the block onto nutrient agar, within 3-10 min or up to ca. 12 h later. Bacteria inoculated onto Plastic blocks were readily recovered for minutes to hours and would multiply if held overnight. Recoveries from wooden blocks were generally less than those from plastic blocks, regardless of new or used status; differences increased with holding time. Clean wood blocks usually absorbed the inoculum completely within 3-10 min. If these fluids contained 103-104 CFU of bacteria likely to come from raw meat or poultry, the bacteria generally could not be recovered after entering the wood. If ≥106 CFU were applied, bacteria might be recovered from wood after 12 h at room temperature and high humidity, but numbers were reduced by at least 98%, and often more than 99.9%. Mineral oil treatment of the wood surface had little effect on the microbiological findings. These results do not support the often-heard assertion that Plastic cutting boards are more sanitary than wood.

Virus transmission via foods begins with fecal shedding of viruses by humans. Foodborne viruses infect perorally: These same agents have alterative fecal-oral routes, including person- to-person transmission and the water vehicle. No zoonotic viruses are transmitted via foods in North America. Viruses rank high among foodborne disease agents in the United States, even though observation, diagnosis, and reporting of foodborne viral disease are inefficient. Risk assessment in developed countries considers viral infection rates and personal hygiene of food handlers, as well as the opportunities for contamination of shellfish and other foods by untreated sewage. Licensing of a vaccine against hepatitis A that could be administered to food handlers in North America would provide an important means of preventing foodborne viral disease. However, the most general concern in preventing all foodborne viral disease is to keep all human fecal contamination out of food.

All viruses known to be normally transmissible through foods and of concern to human health emanate from the human intestine. The outbreaks of hepatitis A and recently of gastroenteritis attributed to Norwalk-like viruses most likely developed from feces-contaminated fingers of infected food handlers or water polluted with feces. With few exceptions no recorded outbreak has depended on the ability of virus to withstand even limited heating in food. New and better methods of detection are needed for hepatitis A and Norwalk viruses in foods. It has been well documented that international trade in food products of animal origin can result in the introduction of animal disease into areas in which the disease does not exist. This fact has given rise to programs of research and development for industrially applicable technology to rid animal products from the agents of animal diseases. The survival of viruses inclusive of etiological agents of foot-and-mouth disease, African swine fever, swine vesicular disease and hog cholera virus is reviewed in this paper and new research approaches are suggested. The general need for additional research of foodborne viruses is discussed.

Viruses are sometimes transmitted through foods. Hepatitis A (HA) and some viral gastroenteritides are the diseases now known to be spread most frequently in this way, but any virus from the human intestines probably could be. Bacterial indicators of fecal contamination show limited correlation with the incidence of viruses in foods, so tests to detect the viruses themselves are needed. The epidemiologic record has led to selection of shellfish (bivalve molluscs) and vegetables and fruits as foods for which test methods should be described, and ground beef and raw milk are also considered here because of the great interest they have attracted among research workers. Viruses in foods are presently detected on the basis of the infections they cause in cultured primate cells, but these cell culture methods do not permit detection of the HA virus nor the most important of the foodborne gastroenteritis viruses. Current methods of virus detection entail liquefaction of the food sample, clarification of the sample suspension, possibly concentration of the clarified food extract, and inoculation of cell cultures; a certain amount of specialized equipment is required for some of these procedures. The inclusion of the proper controls is critical to interpretation of results that are obtained.

This study concerned infections caused by minimal quantities of waterborne enteroviruses. The model system comprised young weanling swine and their homologous enteroviruses; the porcine digestive tract and its enteroviruses are like those of man, and the system affords greater reproducibility and safety than those employing humans or other primates. Subjects swallowed known numbers of viral plaque-forming units (pfu) in 5 ml of drinking water. The body was about 1000 times (600 to 750 for one virus and 1800 to 2500 for another) less likely than a tissue culture to be infected by a given quantity of enterovirus. Doses given after eating, or in four daily portions, produced similar results. No infected animal became ill, despite the reported virulence of the viruses. Chlorination reduced viral infectivity greatly, but short of total extinction, in a single trial. Two newborns were not infected by 20 pfu administered by gavage.

Grape juice inactivated human enteroviruses, but not parainfluenza type 1 (Sendai) virus, in vitro. The effect was not one of aggregation or of degradation of the virus surface. Some of the inactivated virus adsorbed specifically to host cells, but did not infect them. Most of the inactivated virus could be reactivated by treatment with polyethylene glycol. Grape juice-inactivated virus and coproantibody-neutralized virus were both reactivated by contents of porcine stomach and duodenum, which suggests that ingestion of such viruses would lead to intestinal infection. Grape juice-inactivated virus was efficiently reactivated by human blood serum. Ingested grape juice has not been shown likely to prevent or modify human enterovirus infections.

Linguica, a smoked sausage originally from Portugal, is often made in small quantities in California, without inspection. Campylobacter jejuni, Escherichia coli O157:H7, Listeria monocytogenes, Salmonella enterica serotype Newport, and Yersinia enterocolitica were added individually to batter representing California linguica. Batter (≤1 mm thick), heated at 50, 55, and 60 °C, showed decimal reduction times ranging from >10 min for most trials at 50 °C to

Herbs and spices containing essential oils (EOs) in the range of 0.05–0.1% have demonstrated activity against pathogens, such as Salmonella typhimurium, Escherichia coli O157:H7, Listeria monocytogenes, Bacillus cereus and Staphylococcus aureus, in food systems. Application of herbs, spices and EOs with antimicrobial effects comparable to synthetic additives is still remote for three major reasons: limited data about their effects in food, strong odor, and high cost. Combinations of techniques have been successfully applied in several in-food and in vitro experiments. This paper aims to review recent in-food applications of EOs and plant-origin natural antimicrobials and recent techniques for screening such compounds.

In July 1962, the author joined the Food Research Institute (FRI), then at the University of Chicago, to become its food virologist. There was a limited record of waterborne viral disease outbreaks at the time; recorded data on foodborne outbreaks were fewer still. Laboratory environmental (water and wastewater) virology was in its infancy, and food virology was in gestation. Detection of viruses was most often attempted by inoculation of primary primate cell cultures, with observation for plaque formation or cytopathic effects. Focus was initially on enteroviruses and reoviruses. Environmental and food samples had to be liquefied if not already in liquid form; clarified to remove solids, bacteria, and fungi; and concentrated to a volume that could be tested in cell culture. Cytotoxicity was also a concern. Studies at the FRI and some other laboratories addressed all of these challenges. The FRI group was the World Health Organization’s Collaborating Center for Food Virology for many years. Other topics studied were virus inactivation as functions of temperature, time, matrix, disinfectants, and microbial action; peroral and ex-vivo infectivity; and the suitability of various virus surrogates for environmental monitoring and inactivation experiments. Detection of noroviruses and hepatitis A virus required molecular methods, most often RT-PCR. When it was found that inactivated virus often gave the same RT-PCR signal as that of infectious virus, sample treatments were sought, which would prevent false-positive test results. Many laboratories around the world have taken up food and environmental virology since 1962, with the result that a dedicated journal has been launched.

The spectacular achievements and elegance of viral RNA analyses have somewhat obscured the importance of the capsid in transmission of viruses via food and water. The capsid’s essential roles are protection of the RNA when the virion is outside the host cell and initiation of infection when the virion contacts a receptor on an appropriate host cell. Capsids of environmentally transmitted viruses are phenomenally durable. Fortuitous properties of the capsid include antigenicity, isoelectric point(s), sometimes hemagglutination, and perhaps others. These can potentially be used to characterize capsid changes that cause or accompany loss of viral infectivity and may be valuable in distinguishing native from inactivated virus when molecular detection methods are used.

Reliability analysis is especially important when critical decisions are to be made involving potentially severe adverse consequences such as foodborne illness. Owing to uncertainty associated with the parameters controlling survival of Listeria monocytogenes in chorizo (a Mexican-style sausage), the time needed to reduce the count by a certain number (n) of logs (tnD) is probabilistic. In this paper the first-order second-moment (FOSM) method based on Taylor series expansion is used to derive the expected value and standard deviation of tnD as function of the operating conditions (random variables) affecting survival, namely initial water activity (aw0) of the sausage batter, storage temperature (T) and airflow velocity (F), along with their uncertainties characterised by their means and coefficients of variation. For any given n the derived tnD probability distribution enables one to determine an estimate of tnD for any desired level of reliability or confidence level, such as 50% (median value), 95%, 99%, etc. Among the conclusions drawn were: (i) the variability associated with T and F has a minor effect on estimating uncertainty in tnD, whereas the reliability of tnD estimation is greatly influenced by the uncertainty in aw0; and (ii) the uncertainty in aw0 has the greatest impact when aw0 of the sausage formulation exceeds 0.90. The approach used and discussed in this paper can be applied to any survival/inactivation study to incorporate the effect of uncertainty in the various extrinsic and intrinsic parameters on the survival kinetics of the pathogen in a food system under evaluation. Copyright © 2006 Society of Chemical Industry

Using artificial neural networks (ANNs), a highly accurate model was developed to simulate survival curves of Listeria monocytogenes in chorizos as affected by the initial water activity (a(w0)) of the sausage formulation, temperature (T), and air inflow velocity (F) where the sausages are stored. The ANN-based survival model (R(2)=0.970) outperformed the regression-based cubic model (R(2)=0.851), and as such was used to derive other models (using regression) that allow prediction of the times needed to drop count by 1, 2, 3, and 4 logs (i.e., nD-values, n=1, 2, 3, 4). The nD-value regression models almost perfectly predicted the various times derived from a number of simulated survival curves exhibiting a wide variety of the operating conditions (R(2)=0.990-0.995). The nD-values were found to decrease with decreasing a(w0), and increasing T and F. The influence of a(w0) on nD-values seems to become more significant at some critical value of a(w0), below which the variation is negligible (0.93 for 1D-value, 0.90 for 2D-value, and

This study addressed health risks from ethnic sausages produced on a small scale, without inspection, in California and elsewhere. Mexican-style chorizo, a raw pork sausage that is not cured, fermented, or smoked, was contaminated experimentally in the batter with Escherichia coli O157:H7, Listeria monocytogenes, or Salmonella serotypes and stuffed into natural casings. Formulations were based on a market survey in California. Physical parameters that were controlled were pH, water activity (a(w)), and storage temperature. The pH was adjusted with vinegar, stabilizing at 5.0 within 24 h. Initial a(w) levels adjusted with salt were 0.97, 0.95, 0.93, 0.90, and 0.85; levels declined with time because of evaporation. Pathogen numbers declined with storage up to 7 days, with few brief exceptions. Main effects and interactions of constant temperature and pH with declining a(w) on survival of the pathogens were determined. Maximum death rates occurred at higher a(w) for E. coli O157:H7 and Salmonella than for L. monocytogenes. Salt used to adjust a(w) affected palatability. Spices (black pepper, chili pepper, chili powder, cumin, garlic, guajillo pepper, oregano, and paprika) comprised another, potentially significant aspect of the sausage formulation. Some (notably black pepper and cumin) carried an indigenous microflora that contributed significantly to the microbial load of the sausage batter. Only undiluted fresh and powdered garlic exhibited a significant antimicrobial effect on the pathogens. Although each of the tested formulations caused death of the inoculated pathogens, none of the death rates was sufficiently rapid to ensure safety within the probable shelf life of the product.

Three hundred meat samples, recovered from beef neck- and breast-bones using a conventional advanced meat recovery (AMR) system, the de-sinewed minced meat (DMM10) technology, and hand-boning, were collected and tested for presence of central nervous system tissue (CNST) in meat using an ELISA-based test. Samples were collected at two processing facilities (Est. A and B). Sternum meat was the non-CNST reference (control) - it is distant from brain and spinal cord locations on a carcass, with low likelihood of contamination with CNST. Neckbone meat was recovered from bones obtained from carcasses where the spinal cord was removed manually, Est. B, or using a Jarvis circular hydraulic cord remover saw, Est. A. All samples from AMR, DMM, and hand methods showed lower calculated levels of "risk material" than the stated limit of detection (0.1%) of ELISA kit. There was no apparent difference among these, and use of the Jarvis saw had no perceptible advantage.

Time-dependent survival curves of Salmonella spp. in chorizos were modeled using both the classical method of statistical regression and the newly introduced method of artificial neural networks (ANNs). The survival curves were obtained experimentally for chorizos formulated at five initial water activity (Aw0) levels of 0.85, 0.90, 0.93, 0.95 and 0.97, which had been stored under four different storage conditions: in a refrigerator (Ref) at 6C, at room temperature (RT) of 25C, in a hood (Hd) at 25C with forced inflow air circulation velocity F of 25.4 m/min and in an incubator (Inc) at 30C. The developed models enable prediction of survival curves (log count versus time) for Salmonella in chorizos as affected by a given set of operating conditions (Aw0, storage temperature [T] and F). Additionally, both the 1D- and 2D-values (time to reduce the count by 1 and 2 logs, respectively) were derived from a number of simulated survival curves and were used to develop regression models (R2 = 0.980 and 0.977 for 1D- and 2D-value models, respectively) for predicting these two times as a function of operating conditions. Both 1D- and 2D-values increased with increasing Aw0 and decreasing T and F. Additionally, these times were more sensitive to Aw0 when the latter was above 0.940, and F was more influential at higher T. The ANN-based model (R2 = 0.967) outperformed the regression-based model (R2 = 0.919) and was also used to develop models for predicting the 1D- and 2D-values as a function of Aw0, T and F.

Survival of Listeria monocytogenes in chorizos (Mexican-style sausages) was modeled in relation to initial water activity (a w0 ) and storage conditions using the Weibull cumulative distribution function. Twenty survival curves were generated from chorizos formulated at a w0 = 0.85-0.97 then stored under four temperature (T) and air inflow velocity (F) conditions. The Weibull model parameters (α and β) were determined for every curve. Predicted survival curves agreed with experimental curves with R 2 = 0.945-0.992. Regression models (R 2 = 0.981-0.984) were developed to relate a and β to operating conditions. The times to one- and two-log reduction in count (t 1D and t 2D ) were derived from the Weibull model in terms of a and β. A parametric study revealed that L. monocytogenes survival was most sensitive to a w0 between 0.90 and 0.95. The inactivation of L. monocytogenes could be maximized with higher T and lower a w0 ; however, F did not significantly influence survival.

Two commercial immunological kits for detection of central nervous system (CNS) tissue in beef were compared: ScheBo® Brainostic™, based on CNS-specific antigen (neuron specific enolase) detection, and Ridascreen® Risk Material 10/5 test, an enzyme immunoassay for glial fibrillary acidic protein. Spinal cord (SC) was added to batches of choice, select, and utility grades of ground fresh beef shoulder clod to yield 0.0, 0.0125, 0.025, 0.05, 0.1, 0.2, 0.4, 0.8, and 1.6% SC in meat. Sensitivity and specificity in detecting SC in fresh and frozen samples were determined. Both Brainostic™ and Ridascreen® kits detected SC at claimed levels: 0.25% and 0.11%, respectively. The Ridascreen® test consistently detected SC at 0.025%, below its claimed sensitivity level, expressed for brain and SC combined. The Ridascreen® test was ∼10× more sensitive, easier, faster to run and less expensive than the Brainostic™. Overall, quality grade had no influence on SC detection in fresh or frozen meat.

During inactivation of poliovirus type 1 (PV-1) by exposure to UV, hypochlorite, and heat (72°C), the infectivity of the virus was compared with that of its RNA. DEAE-dextran (1-mg/ml concentration in Dulbecco's modified Eagle medium buffered with 0.05 M Tris, pH 7.4) was used to facilitate transfecting PV-1 RNA into FRhK-4 host cells. After interaction of PV-1 RNA with cell monolayer at room temperature (21 to 22°C) for 20 min, the monolayers were washed with 5 ml of Hanks balanced salt solution. The remainder of the procedure was the same as that for the conventional plaque technique, which was also used for quantifying the PV-1 whole-particle infectivity. Plaque formation by extracted RNA was approximately 100,000-fold less efficient than that by whole virions. The slopes of best-fit regression lines of inactivation curves for virion infectivity and RNA infectivity were compared to determine the target of inactivation. For UV and hypochlorite inactivation the slopes of inactivation curves of virion infectivity and RNA infectivity were not statistically different. However, the difference of slopes of inactivation curves of virion infectivity and RNA infectivity was statistically significant for thermal inactivation. The results of these experiments indicate that viral RNA is a primary target of UV and hypochlorite inactivations but that the sole target of thermal inactivation is the viral capsid.

The earliest approaches to detection of viruses in water and in food were derived from those used in diagnostic clinical virology. Early detection methods were based on demonstrable infection of a susceptible host system, ideally a cell culture. Media for primary cell cultures often comprised a balanced salt solution plus an enzymatic hydrolysate of lactalbumin and some blood serum. Virus replication in cell cultures was often demonstrated with the aid of a microscope: death of host cells maintained in fluid medium was called the cytopathic effect. Characterization of the viruses of interest was complicated by the lack of laboratory hosts. Eventually, viruses were classified as having RNA or DNA, as having or lacking a lipid-containing envelope, and by size category. Detection of viruses in food extracts originally implied the use of primary monkey kidney (PMK) cell cultures, as was also done for diagnostic purposes. Propagation of viruses in cell culture and development of the plaque technique introduced much more quantitative precision into inactivation experiments. The bovine spongiform encephalopathy (BSE) epidemic appears to have resulted from a change in the rendering process used in the United Kingdom. The BSE infective agent could be detected in the brain, spinal cord, retina, trigeminal and dorsal root ganglia, tonsils, and distal ileum of symptomatic BSE-infected cattle; but extensive tests have failed to detect it in muscle meat or in milk. Most food-borne viruses are human specific, so this has generally entailed the use of human volunteers.

We report the detection and identification of Cryptosporidium and Giardia from 1 of 3 species of pinnipeds. Fecal samples were collected from Pacific harbor seal (Phoca vitulina richardsi), northern elephant seal (Mirounga angustirostris), and California sea lion (Zalophus californianus) in the northern California coastal area. By means of fluorescently labeled monoclonal antibodies, Cryptosporidium oocysts were detected in 3 samples from California sea lions, 1 of which also contained Giardia cysts. Oocysts of Cryptosporidium and cysts of Giardia were morphologically indistinguishable from oocysts of C. parvum and cysts of G. duodenalis from other animal origins. Oocysts and cysts were then purified using immunomagnetic separation techniques and identified by polymerase chain reaction (PCR), from which species-specific products were obtained. Sequence analysis revealed that the 452-bp and 358-bp PCR products of Cryptosporidium isolated from California sea lion had identities of 98% with sequences of their template fragments of C. parvum obtained from infected calves. Based on morphological, immunological, and genetic characterization, the isolates were identified as C. parvum and G. duodenalis, respectively. The findings suggested that California sea lions could serve as reservoirs in the environmental transmission of Cryptosporidium and Giardia.

Manure is a resource, but sometimes also a nuisance. Manure management strategies have traditionally focused on soil nutrients (N, P, K), COD, and more recently biological substances (antibiotics, hormones, etc.), with disinfection being a relative afterthought. Zoonotic pathogens (Salmonella and other bacteria, protozoa, etc.) may be present in manure, but only occasionally cause foodborne disease. In countries where food is relatively safe, requiring heroic manure disinfection measures may be a net detriment to public health. Decisions that a new, elegant disinfection technology can, should, or must be done may result from invoking the "precautionary principle." Additional capital and operating costs must be passed to the consumer. Since such measures are likely to prevent very few human illnesses, policymakers should also consider the effect of increased prices on human nutrition and hunger. In most situations, not eating is more dangerous than eating.

An exponential linear destruction was observed for Escherichia coli O157:H7 and Salmonella typhimurium in cattle manure and manure slurry stored at 4, 20 or 37 degrees C. The resulting decimal reduction times ranged from 6 days to 3 weeks in manure and from 2 days to 5 weeks in manure slurry. The main effects of time as well as temperature were pronounced with the most rapid destruction at 37 degrees C. The ammonia concentration in manure increased slightly during storage but did not exceed 0.1%. pH values in the deeper layers of manure remained constant except at 37 degrees C when the pH increased by 1 unit in 60 days. In the surface layers of manure, pH increased by 1.5-2 units, the oxidation-reduction potential of the manure declined rapidly to values below -200 mV. These changes do not seem to be reflected in changing rates of bacterial destruction. The observed order of destruction makes it possible to predict storage conditions (temperature and time) that will lead to a predetermined level of reduction of the two pathogens.

Cryptosporidium parvum is a protozoan parasite capable of causing massive waterborne outbreaks. This study was conducted to model the transfer of C. parvum oocysts from contaminated water via food contact surfaces into yogurt and ice-cream, as well as to examine oocyst survival. Propidium iodide staining, combined with a direct immunofluorescence assay, was used for oocyst viability determination. Oocysts were recovered from milk products by a sucrose flotation-based procedure, with average recoveries of 82.3, 60.7, and 62.5% from low (1%) fat milk, 9% fat ice-cream, and 98% fat-free yogurt, respectively. Oocysts were also recovered, by rinsing with tap water, from stainless steel surfaces inoculated with oocyst suspension, with average recoveries of 93.1% when the surface was still wet and 69.0% after the surface had air-dried at room temperature. Viability of oocysts on the surface was significantly affected by desiccation; 5% of the oocysts remained viable after 4 h of air-drying at room temperature, while the proportion of viable oocysts was 81, 69, and 45% after air-drying for 10 min, 1 h, and 2 h, respectively. In contrast, oocyst viability only dropped from 82 to 75% after 30 min contact at room temperature with 5% bleach solution (equivalent to 0.26% NaOCl). Transfer of oocysts from milk and stainless steel surfaces into yogurt, and oocyst survival during the process were analyzed. Yogurt was made from pasteurized low fat milk and live yogurt starter by incubating at 37 degrees C for 48 h and then stored at 4 degrees C. Oocyst viability decreased from 83% (80%) to approximately 60% after 48 h at 37 degrees C and to approximately 58% following 8 days of storage, similar to oocyst survival in the controls using pasteurized milk without the addition of live yogurt. Oocyst survival in ice-cream was investigated by inoculating oocysts into ice-cream mix, and mixing and freezing in an ice-cream freezer, and hardening at -20 degrees C. Although approximately 20% (25 and 18%) of oocysts were viable before hardening, none were viable after 24 h at -20 degrees C. Control samples of oocysts suspended in distilled water and stored at -20 degrees C were taken at the same time intervals and 8% of the oocysts were still viable after 24 h.

Genomic DNA was isolated from Cryptosporidium parvum oocysts by a specific immunomagnetic separation-in vitro excystation procedure and subjected to randomly amplified polymorphic DNA analysis using sequence-independent primers. An estuary C. parvum isolate was easily differentiated from several bovine isolates, while five bovine isolates of the same origin were indistinguishable from each other.

Escherichia coli 0157:H7 has emerged in the past 20 years as a pathogen of public health importance. Although most E. coli are normal flora in the colons of humans and other warm-blooded animals, several strains are capable of causing disease in humans. In recent years, E. coli 0157:H7 and other shiga-like toxin-producing strains have been transmitted via foods and caused disease ranging from bloody diarrhea, and in more severe cases, hemolytic uremic syndrome and thrombocytopenic purpura. The reservoir appears to be cattle and, perhaps, other ruminants. Control is difficult in nonheated foods due to the organism's tolerance to low pH. Only supportive, symptomatic treatment is available for affected humans, and means to eliminate carriage in livestock are not presently available.

We studied the concentration of hepatitis A virus (HAV) from environmental samples by membrane filter-based urea-arginine phosphate buffer and its detection by using immunomagnetic capture (IC) reverse transcription (RT)-PCR (IC PCR). Magnetic beads coated with anti-HAV rabbit antibodies were used for enrichment and concentration of HAV from environmental samples. IC PCR is sensitive enough to detect as few as 0.04 PFU of cell culture-adapted HAV in inoculated water and sewage samples. IC PCR is specific and does not yield positive reactions with poliovirus 1, HAV RNA, or selected bacteriophages. IC concentrates viruses suspended in small volumes to microliter volumes that can be used directly in RT-PCR. IC concentration of viruses from sewage samples without concentration of inhibitory substances is important for successful RT-PCR detection. In a field trial, 2 of 18 raw sewage samples tested by IC PCR were positive for HAV.

Several outbreaks of foodborne and waterborne illness have directed the nation's attention to intestinal pathogens that are threats to public health. Among these pathogens are Cryptosporidium parvum and Escherichia coli O157:H7, which are known to infect and to be spread by not only humans, but also livestock and various species of wildlife. New regulations aimed at controlling these pathogens are being implemented, despite a shortage of scientific information about their ecology, how they contaminate food and water supplies, and how to detect and eliminate such contamination. Research is needed to address these issues and to develop better technologies for pathogen detection, water treatment and food processing.

Viruses are transmitted in foods as inert, submicroscopic particles that come from the human intestines. Serologic and molecular detection methods have been devised for the detection of hepatitis A and small, round, structured gastroenteritis viruses in feces, but are not yet applicable for their detection in foods. The control of viral transmission via foods still depends greatly upon preventing contamination or on the thorough cooking of virus-contaminated food.

Decontamination of Plastic and wooden cutting boards was studied, with a view to preventing cross-contamination of foods in home kitchens. New and used Plastic (four polymers plus hard rubber) and wood (nine hardwoods) boards were cut into 5-cm square blocks (25 cm2 area) for these experiments. Bacterial contaminants-- Escherichia coli (two nonpathogenic strains plus serotype O157:H7), Listeria innocua , L. monocytogenes , or Salmonella typhimurium --applied to the block surface in nutrient broth or chicken juice, were recovered by soaking the surface in nutrient broth or pressing the block onto nutrient agar, within minutes or ≥12 h later. Persistence and overnight multiplication of bacteria on plastic surfaces depended on maintenance of humidity so as to prevent drying of the contaminant. New plastic cutting surfaces were relatively easy to clean and were microbiologically neutral, but plastic boards with extensive knife scars were difficult to clean manually, especially if they had deposits of chicken fat on them. Fewer bacteria were generally recovered from wooden blocks than from plastic blocks. Clean wood blocks rapidly absorbed all of the inoculum, after which the bacteria could not be recovered within 3 to 10 min. If the board surface was coated with chicken fat, some bacteria might be recovered even after 12 h at room temperature and high humidity. Cleaning with hot water and detergent generally removed these bacteria, regardless of bacterial species, wood species, and whether the wood was new or used.

Wastewater treated to the secondary level may not be disinfected before discharge—if the receiving waterway is not a source of drinking water‐during periods cold enough to limit recreational use. Samples were collected from a wastewater treatment plant and its receiving waterway during periods when ultraviolet disinfection of the effluent was and was not being done. Levels of Escherichia coli, fecal coliforms, and enterococci were reduced by 2 to 3 log units (99 to 99.9%) in treatment, and by more than another log unit (total 99.99% or more) with disinfection. At a sampling site ca. 30 km downstream from the outfall, levels of E. coli and fecal coliforms, but not of enterococci, were significantly higher when the ultraviolet was off. Incidence of Salmonella spp. along the waterway was not firmly related to disinfection. Probable public health effects of not disinfecting during the cold months were not clearly predictable.

This study was conducted to determine the persistence of Giardia lamblia cysts in mixed septic tank effluent and swine manure slurry and to correlate fluorescein diacetate-propidium iodide staining of G. lamblia cysts with their morphology under low-voltage scanning electron microscopy. Under field conditions, G. lamblia cysts were degraded more rapidly in the mixed waste than in the control Dulbecco's phosphate-buffered saline (PBS). For total and viable cysts, the mixed waste had D values (time for a 90% reduction in number of cysts) of 18.3 and 15.5 days, and the Dulbecco's PBS control had D values of 41.6 and 26.8 days. The rates of cyst degradation in septic tank effluent and in Dulbecco's PBS were similar. Increasing the proportion of swine manure slurry in the mixed waste favored degradation of the parasite. These results indicate that the mixed waste treatment was the predominant factor affecting the cyst persistence and that it was swine manure slurry that played the role of degrading the parasite. Visualization of viable and nonviable Giardia cysts with low-voltage scanning electron microscopy revealed an excellent correlation between the viability of the cysts determined by fluorescein diacetate-propidium iodide staining and their electron microscopic morphology.

Enterohemorrhagic Escherichia coli serogroup 0157:H7 is harbored by cattle and causes bloody diarrhea and hemolytic uremic syndrome in persons who consume raw milk and under-cooked beef. Samples of manure from Wisconsin dairy farms were tested for the presence of E. coli 0157:H7 as well as for bacteriophages (coliphages) specific for this microorganism. No E. coli 0157:H7 bacteria were isolated from any of the 21 manure samples taken from 12 farms. Nineteen of 20 samples yielded "nonspecific" coliphages that produced plaques both on 0157:H7 and on other E. coli . Only one sample yielded a coliphage that plaqued on 14 strains of 0157:H7 but not on other E. coli . This coliphage, designated "AR1," is tailed and ca. 187 nm long; it produces distinct plaques ca. 0.5 mm in diameter; single-step growth experiments showed a latent period of 20 to 25 min and a burst size of 34 progeny plaque-forming units (PFU). AR1 was also tested against other enterobacteria, including: Escherichia hermanii , four species of Salmonella , four types of Yersinia enterocolitica , and a strain of Shigella dysenteriae which produces an enteric toxin similar to that produced by E. coli 0157:H7. Of these enteric bacteria, only S. dysenteriae yielded plaques, which suggests that there is a relationship between production of this toxin and susceptibility to coliphage AR1. Coliphage AR1 may be useful in detecting or identifying E. coli 0157:H7 and possibly other bacteria producing the same toxin, from human stool, animal manure, and food samples.

Resources for ensuring the safety of food in the State of Wisconsin, USA, have been briefly surveyed. It is noted that agriculture ranks third behind manufacturing and tourism in the economy of Wisconsin, but the state ranks especially high in the production of milk and cheese. Control and inspection of meat, milk, and other foods from the farm through processing and eventual sale in Wisconsin, other states, or outside the USA are the responsibility of various government agencies. Food that is produced and sold entirely within Wisconsin is supervised by state agencies—especially the Department of Agriculture, Trade and Consumer Protection. Foods that will be sold outside the state are regulated by federal agencies—especially the Food and Drug Administration and the US Department of Agriculture. Strong penalties can be imposed on anyone found handling food in a way that causes a health risk.

Animal feeds may be contaminated, accidentally or maliciously, with a number of zoonotic bacteria. Animal infections with these bacterial agents, whether or not they cause animal disease, may lead to human illnesses. Anhydrous ammonia was introduced on farms in developed countries as a high-nitrogen soil amendment, but later found use in enhancing crude protein in low-quality roughage fed to ruminants and in neutralizing mycotoxins in fungus-infested feed grains. Although ammonia has been known to be effective against bacteria in other contexts (e.g., manure, community sewage sludge, seeds for sprouting, and boneless lean beef trimmings), it appears that the antibacterial effect of ammoniating animal feeds had not been tested. In the present study, samples of roughage (wheat straw, corn silage) and concentrates (corn grain, cottonseed) produced as animal feed were contaminated with dried-on zoonotic bacteria (Salmonella Newport in all; Campylobacte jejuni, E. coli O157:H7, Listeria monocytogenes, Yersinia enterocolitica in corn grain only). Disinfection with anhydrous ammonia gas was conducted for 24 h at room temperature ( 25 degrees C). The treatment was least effective in silage because the silage alone showed strong antibacterial activity, which may have been slightly reduced by ammoniation. In the other three feeds, depending on the initial level of contamination, ammonia destruction of >or= 5 log10 cfu/g (99.999%) of the selected contaminant was usually observed.

Cutting boards are commonly perceived as important fomites in cross-contamination of foods with agents such as Salmonella spp., despite the lack of supporting epidemiological data. A variety of woods and plastics have been used to make work surfaces for cutting. In general, wood is said to dull knives less than plastic, and plastic is seen as less porous than wood. Research to model the hypothetical cross-contamination has been done in a variety of ways and has yielded a variety of results. At least some of the work with knife-scarred plastic indicates that the surface is very difficult to clean and disinfect, although this may vary among the polymers used. High-density polyethylene, which is most used in commercial applications, has been shown to delaminate in response to knife scarring. Wood is intrinsically porous, which allows food juices and bacteria to enter the body of the wood unless a highly hydrophobic residue covers the surface. The moisture is drawn in by capillary action until there is no more free fluid on the surface, at which point immigration ceases. Bacteria in the wood pores are not killed instantly, but neither do they return to the surface. Destructive sampling reveals infectious bacteria for hours, but resurrection of these bacteria via knife edges has not been demonstrated. Small plastic cutting boards can be cleaned in a dishwasher (as can some specially treated wooden boards), but the dishwasher may distribute the bacteria onto other food-contact surfaces. Most small wooden boards (i.e., those with no metal joiners in them) can be sterilized in a microwave oven, but this should be unnecessary if accumulation of food residues is prevented. However, 2 epidemiological studies seem to show that cutting board cleaning habits have little influence on the incidence of sporadic salmonellosis. Further, one of these studies indicated that use of plastic cutting boards in home kitchens is hazardous, whereas use of wooden cutting boards is not.

Mexican-style raw meat sausages (chorizos) are not regulated in California when they are produced in small ethnic food markets. These sausages are sold uncooked, but their formulation imparts a color that may lead the consumer to assume that they are already cooked, and thus the chorizos may sometimes be eaten without proper cooking. If pathogens are present in such cases, illness may result. Survival of Salmonella and Escherichia coli O157:H7 in chorizos was evaluated under different storage conditions selected based on an initial survey of uninspected chorizos in California. Chorizos were formulated with five different initial water activity (aw) values (0.85, 0.90, 0.93, 0.95, and 0.97), stored under four conditions (refrigeration at 6 to 8 degrees C, room temperature at 24 to 26 degrees C, under a hood at 24 to 26 degrees C with forced air circulation, and incubation at 30 to 31 degrees C with convective air circulation), and sampled after 1, 2, 4, and 7 days. The initial pH was 4.8 and remained near 5.0 from day 1 of the sampling period. Two separate studies of packs inoculated with five-strain cocktails of Salmonella and of E. coli O157:H7 were performed twice for each initial aw. The three lowest aw values (0.85, 0.90, and 0.93) and the incubation and hood storage conditions were more effective (Por = 0.05) at reducing the target pathogen levels in chorizos than were the two highest aw values (0.95 and 0.97) and the refrigeration storage condition, regardless of storage time. These results provide a scientific basis for guidelines given to producers of uninspected chorizo and should reduce the probability of foodborne illness associated with these products.

Chorizos-Mexican-style raw-meat sausages-are a concern in California because their production in small ethnic food markets is unregulated. Their formulation may cause them to appear cooked to the consumer, who may eat the raw sausage without prior proper cooking. Bacterial pathogens in such products may cause illness or even death. Survivability of Listeria monocytogenes in chorizos was evaluated under different storage conditions selected on the basis of an initial survey of uninspected chorizos in California. Sausages were formulated to five different initial water activity (aw) levels (0.85, 0.90, 0.93, 0.95, 0.97), stored under four conditions (refrigeration, "Ref," 6 to 8 degrees C under convective air circulation; room temperature, "RT," 24 to 26 degrees C under convective air circulation; hood, "Hd," 24 to 26 degrees C under forced air circulation; and incubation, "Inc," 30 to 31 degrees C under convective air circulation), and sampled after 1, 2, 4, and 7 days. The initial pH was 4.8 and remained near 5.0 from day 1 of the sampling period. An inoculated-pack study using a five-strain cocktail of L. monocytogenes was performed twice for each initial aw. Results indicated that the three lowest initial aw levels (0.85, 0.90, 0.93) and the Hd and Inc storage conditions were more effective (Por = 0.05) at reducing L. monocytogenes levels in chorizos than the two highest initial aw levels (0.95 and 0.97) and the Ref storage condition, irrespective of storage time. These results can provide a scientific basis for guidelines given to uninspected chorizo producers in California and reduce the risk of foodborne illness.

The survival of Salmonella spp. in chorizos has been studied under the effect of storage conditions; namely temperature (T=6, 25, 30 degrees C), air inflow velocity (F=0, 28.4 m/min), and initial water activity (a(w0)=0.85, 0.90, 0.93, 0.95, 0.97). The pH was held at 5.0. A total of 20 survival curves were experimentally obtained at various combinations of operating conditions. The chorizos were stored under four conditions: in the refrigerator (Ref: T=6 degrees C, F=0 m/min), at room temperature (RT: T=25 degrees C, F=0 m/min), in the hood (Hd: T=25 degrees C, F=28.4 m/min), and in the incubator (Inc: T=30 degrees C, F=0 m/min). Semi-logarithmic plots of counts vs. time revealed nonlinear trends for all the survival curves, indicating that the first-order kinetics model (exponential distribution function) was not suitable. The Weibull cumulative distribution function, for which the exponential function is only a special case, was selected and used to model the survival curves. The Weibull model was fitted to the 20 curves and the model parameters (alpha and beta) were determined. The fitted survival curves agreed with the experimental data with R(2)=0.951, 0.969, 0.908, and 0.871 for the Ref, RT, Hd, and Inc curves, respectively. Regression models relating alpha and beta to T, F, and a(w0) resulted in R(2) values of 0.975 for alpha and 0.988 for beta. The alpha and beta models can be used to generate a survival curve for Salmonella in chorizos for a given set of operating conditions. Additionally, alpha and beta can be used to determine the times needed to reduce the count by 1 or 2 logs t(1D) and t(2D). It is concluded that the Weibull cumulative distribution function offers a powerful model for describing microbial survival data. A comparison with the pathogen modeling program (PMP) revealed that the survival kinetics of Salmonella spp. in chorizos could not be adequately predicted using PMP which underestimated the t(1D) and t(2D). The mean of the Weibull probability density function correlated strongly with t(1D) and t(2D), and can serve as an alternative to the D-values normally used with first-order kinetic models. Parametric studies were conducted and sensitivity of survival to operating conditions was evaluated and discussed in the paper. The models derived herein provide a means for the development of a reliable risk assessment system for controlling Salmonella spp. in chorizos.