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Enteric virus contamination of foods through industrial practices: a primer on intervention strategies.

Hepatitis A and E viruses, rotaviruses, Norwalk-like caliciviruses, and astroviruses are among the enteric viruses known to cause food- and waterborne illness. These viruses are spread by the fecal-oral route and are a major cause of morbidity and mortality worldwide. Foods may be contaminated at any time pre- or post-harvest; however, many outbreaks are associated with foods handled by infected restaurant workers. Produce may be contaminated by improper irrigation or fertilization practices, by the hands of infected pickers or processors, or as the result of adulteration during any stage of handling. Outbreaks have been commonly associated with foods which are served raw or only lightly cooked, such as molluscan shellfish, fruits and vegetables, and salads or products contaminated after cooking like frosted bakery products. The farming, shellfish, processing, transportation, and restaurant industries must maintain vigilance to reduce outbreaks of enteric virus illness. Intervention strategies to enhance product safety include increased industry and consumer education; changes in industrial practices, product management, and processing technologies; worker immunizations; and the development of improved monitoring tools for the detection of enteric viruses in foods.

Caliciviridae Infections↗

Acute diarrhea associated with travel.

Travelers' diarrhea, an acute illness that affects between 20 and 50 percent of travelers to high-risk areas, is usually acquired by eating contaminated food, drinking contaminated water, or coming in contact with the contaminated hands of an infected person. Travelers' diarrhea can be caused by bacterial, viral, and parasitic agents. The Travelers' Diarrhea Consensus Conference has recommended prophylactic measures, which include proper preparation of food and beverages, nonantimicrobial agents, and antimicrobial agents. The newer quinolone antibiotics and bismuth subsalicylate may also be useful prophylactically. Appropriate treatment methods include oral fluids and electrolyte replacement, nonspecific agents such as bismuth subsalicylate, antimotility agents such as loperamide hydrochloride and diphenoxylate hydrochloride, and antimicrobial and antiparasitic agents.

Acute Disease↗

Evaluation of staphylococcal thermonuclease (TNase) assay as a means of screening foods for growth of staphylococci and possible enterotoxin production.

Samples of food, naturally and artificially contaminated with Staphylococcus aureus, were analyzed for enterotoxin and thermonuclease (TNase). With the exception of egg, all naturally contaminated foods with detectable amounts of staphylococcal enterotoxin were positive for TNase. The enzyme was also present in the majority of foods with over 1 million S. aureus cells per gram. In artificially contaminated foods. TNase was detected in all samples except egg, acidic foods in which growth of S. aureus was suppressed, and some samples of raw ground beef. Recovery of TNase was influenced by the type of food.

Enterotoxins↗

Evaluating multimedia/multipathway model intake fraction estimates using POP emission and monitoring data.

This paper presents a structured evaluation of a novel multimedia chemical fate and multi-pathway human exposure model for Western Europe, IMPACT 2002, using data for PCDD/F congeners. PCDD/F congeners provide an illustration of the potential use of POPs (Persistent Organic Pollutant) data for the evaluation of such models. Based on available emission estimates, model predictions with and without spatial resolution are evaluated at three different stages against monitored data: at environmental contamination levels, food exposure concentration, and in terms of human intake fractions (iF): the fraction of an emission that is taken in by the population. The iF is approximately 3.5.10(-3) for emissions of dioxin in Western Europe. This iF compares well to the traditional non-spatial multi-media/-pathway model predictions of 3.9.10(-3) for the same region and to 2.10(-3) for the USA. Approximately 95% of the intake from Western European emissions occurs within the same region, 5% being transferred out of the region in terms of food contaminants and atmospheric advective transport.

Air Pollution↗

[Epidemiology of human Listeria infections in France].

Human listeriosis is a relatively rare but serious disease with case fatality rates between 20 and 30%. The majority of patients who have listeriosis present with meningitis or septicaemia. Listeriosis during pregnancy can lead to a congenital infection, neonatal sepsis and meningitis or foetal death. The main mode of transmission is through contaminated foods. The infection usually occurs sporadically but small outbreaks and even large epidemics have occurred in a large number of industrialised countries. During the last 10 years several Listeria monocytogenes control measures have been introduced and implemented at the retail level and in production for plants or foods potentially contaminated with Listeria monocytogenes. During this period the incidence of listeriosis decreased substantially and is at present estimated at 300-400 cases annually.

Food Contamination↗

Bioassays for the detection of growth-promoting agents, veterinary drugs and environmental contaminants in food.

Residues of growth-promoting agents, veterinary drugs and environmental contaminants in food products are routinely analyzed with chemical-analytical methods, using physical and spectrometric properties of a compound. Since residue limits are in general based on biological properties of compounds, bioassays offer in theory a good alternative. As a consequence, these assays are much more suitable for the detection of mixtures of compounds with common biological properties, including possibly unknown agonists. Using modern molecular biological techniques, a new generation of bioassays has been developed, showing in general a higher sensitivity and specificity for the target compounds. The CALUX (chemical activated luciferase expression) assay was developed for the detection of polyhalogenated compounds, based on their affinity for the aryl hydrocarbon (Ah) receptor. This paper focuses on the specificity of the assay. The benzimidazole compounds oxfendazole, fenbendazole, febantel, thiabendazole, mebendazole, omeprazole, lanzoprazole and benomyl were shown to give a positive response in the assay. Similar results were obtained with dexamethasone, corticosterone and cortisol, which in addition were able to enhance the response obtained with TCDD. Similarly to the flavonoids alpha- and beta-naphtoflavone, the reported Ah receptor antagonist 4-amino-3-methoxyflavone showed a strong positive response at a concentration of 400 microM, but failed to inhibit the response obtained with TCDD. It is concluded that the chances of false-negative results appear to be minimal and can be recognized. False-positive or, better, unwanted results are in theory more likely to occur. Possible solutions to avoid or detect these type of results are discussed. In general, these kinds of assays offer great possibilities for screening of food samples. In addition to the further optimization of these assays, future work should be focused on the development of rapid, sample and selective extraction procedures.

Animals↗

The threshold of regulation and its application to indirect food additive contaminants in recycled plastics.

Recycled plastics have been used in food-contact applications since 1990 in various countries around the world. To date, there have been no reported issues concerning health or off-taste resulting from the use of recycled plastics in food-contact applications. This is due to the fact that the criteria that have been established regarding safety and processing are based on extremely high standards that render the finished recycled material equivalent in virtually all aspects to virgin polymers. The basis for this conclusion is detailed in this document.

Conservation of Natural Resources↗

Chemical contaminants in foods: some analytical considerations.

Data on the incidence and levels of chemical contaminants in foods are needed for continuous assessment of the safety of the food supply and to inform the public about the safety of food. A larger share of the total analytical resource--federal and state government, private sector, and academia--could profitably be directed to collection and publication of data on the occurrence of chemical contaminants in foods. The quest for more data must be accompanied by measures to ensure data reliability and comparability and to estimate the uncertainty of measurements. Research to improve the efficiency of analysis may be the top priority for future methods improvement studies. Analytical chemistry will continue to be an essential factor in assuring a safe food supply and in communicating to the public accurate information and conclusions about food safety.

DDT↗

PCR-restriction fragment length analysis of aflR gene for differentiation and detection of Aspergillus flavus and Aspergillus parasiticus in maize.

Contamination of food and feedstuffs by Aspergillus species and their toxic metabolites is a serious problem as they have adverse effects on human and animal health. Hence, food contamination monitoring is an important activity, which gives information on the level and type of contamination. A PCR-based method of detection of Aspergillus species was developed in spiked samples of sterile maize flour. Gene-specific primers were designed to target aflR gene, and restriction fragment length polymorphism (RFLP) of the PCR product was done to differentiate Aspergillus flavus and Aspergillus parasiticus. Sterile maize flour was inoculated separately with A. flavus and A. parasiticus, each at several spore concentrations. Positive results were obtained only after 12-h incubation in enriched media, with extracts of maize inoculated with A. flavus (101 spores/g) and A. parasiticus (104 spores/g). PCR products were subjected to restriction endonuclease (HincII and PvuII) analysis to look for RFLPs. PCR-RFLP patterns obtained with these two enzymes showed enough differences to distinguish A. flavus and A. parasiticus. This approach of differentiating these two species would be simpler, less costly and quicker than conventional sequencing of PCR products.

Aspergillus↗

Influence of environmental factors on the biosynthesis of type B trichothecenes by isolates of Fusarium spp. from Spanish crops.

Various species of Fusarium can produce trichothecene mycotoxins that contaminate food commodities and can represent a risk for human and animal health. In this paper, a full factorial design was applied to study the influence of incubation temperature, water activity (a(w)) and type of isolate on the production of deoxynivalenol (DON), nivalenol (NIV) and 3-acetyldeoxynivalenol (3-AcDON) in corn kernel cultures by three isolates of Fusarium graminearum and three isolates of Fusarium culmorum from crops grown in Spain. The tested temperatures were 15, 20, 28 and 32 degrees C. The a(w)-values were 0.960, 0.970 and 0.980. Moisture of cultures (within the studied range) did not affect significantly production of trichothecenes; however, the temperature affected significantly mycotoxin production and the optimal values were 28, 20 and 15 degrees C for DON, NIV and 3-AcDON, respectively. Four additional isolates of F. graminearum and two additional isolates of F. culmorum were examined for production of these mycotoxins at the optimal temperatures. Of the seven isolates of F. graminearum, four produced DON (0.88-3.97 microg/g), seven produced NIV (1.53-124 microg/g), and three produced 3-AcDON (0.65-10.6 microg/g). Of the five isolates of F. culmorum, four produced DON (1.20-4.93 microg/g), four produced NIV (6.94-701 microg/g), and four produced 3-AcDON (0.83-7.70 microg/g). Practically all isolates seem to belong to the NIV-chemotype. This is the first study done with regard to interaction between strain and ecological variables on type B trichothecene production by isolates of these two species from crops grown in Spain.

Food Contamination↗

Two primer pairs to detect OTA producers by PCR method.

Fungi contaminating foods and feeds may produce many mycotoxins including ochratoxin A (OTA). Early and rapid detection of potential OTA producing fungi is important to reduce the negative impacts of OTA. In this study, two PCR specific primer pairs, AoLC35-12L/AoLC35-12R and AoOTAL/AoOTAR, were designed from a DNA sequence of a polyketide synthase gene in Aspergillus ochraceus NRRL 3174. On 14 different fungi tested by PCR, AoLC35-12L/AoLC35-12R amplified a unique band from either OTA or citrinin producers while AoOTAL/AoOTAR amplified one PCR product only from A. ochraceus. So these primers could be used to detect both OTA and citrinin producing fungi (AoLC35-12L/AoLC35-12R) or only A. ochraceus (AoOTAL/AoOTAR) from foodstuffs using PCR method.

Amino Acid Sequence↗

Prevalence and antimicrobial resistance of Campylobacter isolated from retail raw chicken and beef meat, Tehran, Iran.

Campylobacter spp. is a leading cause of human diarrhea. The common source of infection is contaminated food, particularly poultry. The veterinary use of antimicrobial drugs has been suggested to be largely responsible for resistance in human isolates of this zoonotic pathogen. From April to October 2004, 241 samples of chicken and beef meat for sale in retail outlets in Tehran (Iran) were analyzed for the presence of Campylobacter. Totally, 88 (36.5%) Campylobacter strains were isolated. Campylobacter was isolated from a significantly larger number of chicken (63%) than beef (10%) meat (P < 0.0001). Susceptibilities of 72 strains were determined for eight antimicrobial drugs using the disk diffusion assay. Resistance to nalidixic acid was the most common finding (75%), followed by resistance to ciprofloxacin (69.4%), tetracycline (45.8%), amoxicillin (11.1%), streptomycin (4.2%), chloramphenicol (2.8%) and gentamicin (1.4%). None of the isolates was resistant to erythromycin. Multidrug resistance was seen in 75% of the Campylobacter strains.

Animals↗

Modelling the individual cell lag time distributions of Listeria monocytogenes as a function of the physiological state and the growth conditions.

The individual cell lag time distributions of Listeria monocytogenes were characterized for 54 combinations of 22 initial physiological states, 18 growth conditions, and 11 strains. The individual cell lag times were deduced from the times for cultures issued from individual cells to reach an optical density threshold. The extreme value type II distribution with a shape parameter set to 5 was shown effective to describe the 54 observed distributions. The theoretical distributions of individual lag times were thus predictable from the observed means and standard deviations of cell lag times. More interestingly, relationships were proposed to predict the mean and the standard deviation of individual cell lag times from population lag times observed with high initial concentration experiments. The observed relations are consistent with the constancy of the product of the growth rate by the lag time at the cell level for a given physiological state when growth conditions are varying. This product, k, is thus representative of the cell physiological state. The proposed models allow the prediction of individual cell lag time distributions of L. monocytogenes in different growth conditions. We also observed that, whatever the stress encountered and the strains used, the coefficient of variation of the distributions of k was quite constant. These results could be used to describe the variability of the behaviour of few cells of L. monocyotgenes contaminating foods and stressed in the environment of food industry or by food processing.

Colony Count, Microbial↗

Mechanism of action of sphingolipids and their metabolites in the toxicity of fumonisin B1.

Fumonisins are a group of mycotoxins produced primarily by Fusarium moniliforme. Several fumonisins have been isolated through out the years but only fumonisin B1, B2 and B3 are the ones present in naturally contaminated foods, with B1 being the most toxic between them. The structural similarity between sphinganine and fumonisin B1 suggests that the mechanism of action of this mycotoxin is mainly via disruption of sphingolipid metabolism, this is an important step in the cascade of events leading to altered cell growth, differentiation and cell injury. Sphingolipids are a second type of lipid found in cell membranes, particularly nerve cells and brain tissues. Toxicity of fumonisin B1 is given via inhibition of ceramide synthase that catalyzes the formation of dihydroceramide from sphingosine. This mechanism of action may explain the wide variety of health effects observed when this mycotoxin is ingested like high rate of human oesophageal cancer and promotion of primary liver cancer.

Carcinogens, Environmental↗

Comparative macrorestriction and RFLP analysis of Mycobacterium avium subsp. avium and Mycobacterium avium subsp. hominissuis isolates from man, pig, and cattle.

In Germany, tuberculous lesions in slaughtered pigs due to infection with members of the Mycobacterium avium complex are increasingly reported. Contaminated food originating from pig or other livestock is discussed as potential source of human infection. M. avium isolates from man (n=45), pig (n=29), and cattle (n=13) were characterised by restriction fragment length polymorphism (RFLP) with respect to insertion sequences IS1245 and IS901 as well as by XbaI-based pulsed-field gel electrophoresis (PFGE) and the results were compared by computer cluster correlation analysis, to determine potential sources of infection in man. By PCR, 55% of animal isolates was identified as M. avium subsp. avium, and 45% as M. a. hominissuis. All human isolates belonged to M. a. hominissuis. IS1245-RFLP and PFGE resulted in two distinct main groupings reflecting the two subspecies, and dividing the isolates into several subgroups. Animal isolates of M. a. hominissuis were widely distributed within the subgroups of human isolates. M. a. avium isolates, further discriminated by IS901-RFLP, formed host-associated subgroups for animals. Comparison of RFLP patterns with those of PFGE resulted in different subgroups as well as different pairs of isolates with high similarities. Only two isolates exhibited identical patterns by both methods. In general, results of both methods support the possibility that M. a. hominissuis isolates from livestock represent a source of infection for man, probably by common environmental reservoirs. There was no evidence of human infections caused by M. a. avium in Germany.

Animals↗

Spoilage fungi and their mycotoxins in commercially marketed chestnuts.

A nationwide survey was carried out to assess mould spoilage of Castanea sativa nuts sold in Canadian grocery stores in 1998-99. Morphological and cultural characters, along with secondary metabolite profiles derived from thin-layer chromatography, were used to sort and identify fungi cultured from nut tissue. Three mycotoxigenic fungi dominated (Penicillium crustosum, Penicillium glabrum/spinulosum and Penicillium discolor) and were isolated at frequencies of 67.1%, 18.6% and 17.7%, respectively, from a total sample size of 350 nuts. Another mycotoxin producer, Aspergillus ochraceus was also isolated, but at a much lower frequency. HPLC and diode array detection were used to confirm the suspected presence of the mycotoxins penitrem A, chaetoglobosin A and C, emodin and ochratoxin A in extracts prepared from naturally infected nut tissue. To the best of our knowledge, this is the first time emodin has been found in a naturally contaminated food source.

Aspergillus ochraceus↗

Fumonisin production by Gibberella fujikuroi strains from Pinus species.

Fumonisins are important mycotoxins basically produced by strains from the Gibberella fujikuroi species complex (with anamorphs in Fusarium genus) which contaminate food and feed products representing a risk to human and animal health. In this work, we report for the first time the fumonisin production of Fusarium moniliforme Sheldon strains associated to edible pine nuts of Pinus pinea. P. pinea is an important and widely distributed Pinus species in the Mediterranean area where their pine nuts are consumed raw or slightly processed in diverse food products. In this work, characterization and further identification of those strains were performed by polymerase chain reaction-restriction fragment length polymorphisms (PCR-RFLPs) of the intergenic spacer region of the rDNA (IGS) with the aid of the eight mating populations (A-H) described for G. fujikuroi species complex. The method was powerful to detect polymorphism, allowing discrimination between individuals and could be used to study the genetic relationships among them and within the G. fujikuroi species complex. Fusarium strains associated to Pinus radiata were also included in the present study. These strains did not produce fumonisins and showed no close relation with the strains isolated from P. pinea. The approach used in this work was rapid and proved to be efficient to assist identification and to characterize and analyse relatedness of new isolates within the G. fujikuroi species complex.

Chromatography, High Pressure Liquid↗

Outbreak of Salmonella enteritidis gastroenteritis: investigation by pulsed-field gel electrophoresis.

OBJECTIVE: Pulsed-field gel electrophoresis (PFGE) was used to investigate an outbreak of gastroenteritis caused by Salmonella enteritidis. The outbreak occurred among university undergraduates who consumed contaminated food. METHOD: Molecular typing was done by analyzing DNA band patterns of isolates of S. enteritidis after digestion of chromosomal DNA with infrequently-cutting restriction endonucleases XbaI, AvrII, and SpeI and separation of DNA fragments using PFGE. RESULTS: Twenty-nine outbreak isolates of S. enteritidis had identical or highly similar PFGE patterns, whereas different PFGE patterns were observed among three epidemiologically unrelated isolates obtained during the same period. CONCLUSION: The data obtained confirm the value of PFGE in epidemiologic investigations of outbreaks caused by S. enteritidis.

Adult↗