Quantitative microbiological risk assessment: principles applied to determining the comparative risk of salmonellosis from chicken products

Since causal links have been established between food-borne illness and particular microorganisms, it has been possible to assess the public health risks of their presence in foods and propose measures to ensure the safety of customers. Effective control measures for food safety have been based on knowledge of the resistance of pathogenic microorganisms to the treatments used for preservation (e.g. acidification or reduced water activity) or decontamination (e.g. pasteurisation or sterilisation). Using this principle, food safety has been managed informally and successfully within the food industry for many years. Recently, formal risk assessment schemes, for example from Codex Alimentarius, have developed and placed the elements of decision-making on suitable control measures into a formal framework with clearly identifiable stages. The output of the four stages of a formal risk assessment (hazard identification, hazard characterisation, exposure assessment and risk characterisation) provides the basis for decisions on actions needed to control the identified hazard. There are many difficulties in ensuring that risk assessments are realistic and accessible to potential users, in many cases their value is limited by the data available. The study reported here on control of Salmonella in poultry products illustrates that it is possible to produce a comparative risk assessment based on published data. This study is not a full quantitative risk assessment, but provide useful pointers for a risk manager. Differences are discussed between the exposure assessment data needed to propose controls for infectious or toxigenic pathogens. For infectious pathogens, the presence of viable and infectious microorganisms is itself the hazard, but for toxigenic microorganisms, absence or destruction of viable cells at ingestion does not in itself ensure the absence of toxin. For toxin hazards, exposure assessment needs to consider previous conditions that may have led to toxin formation and persistence, rather than just the level of microbes at ingestion.     

Clostridium botulinum and the safety of minimally heated, chilled foods: an emerging issue?

Foodborne botulism is caused by consumption of preformed botulinum neurotoxin, with as little as 30 ng of neurotoxin being potentially lethal. Consumption of minute quantities of neurotoxin-containing food can result in botulism. In view of the severity of foodborne botulism, it is essential that new foods be developed safely without an increase in incidence of this disease. Minimally heated, chilled foods are a relatively new type of food, sales of which are currently increasing by about 10% per annum. These products meet consumer demand for high-quality foods that require little preparation time. Their safety and quality depends on mild heat treatment, chilled storage, restricted shelf life and sometimes on intrinsic properties of the foods. The principal microbiological hazard is nonproteolytic Clostridium botulinum, and there is a concern that this may become an emerging issue. A considerable amount of research and development over the last 15 years has underpinned the safe production of commercial, minimally heated, chilled foods with respect to foodborne botulism, and it is essential that safe food continues to be developed. In particular, the desire to use lighter heat processes and a longer shelf life presents a challenge that will only be met by significant developments in quantitative microbiological food safety.     

New Elements To Consider When Modeling the Hazards Associated with Botulinum Neurotoxin in Food

Botulinum neurotoxins (BoNTs) produced by the anaerobic bacterium Clostridium botulinum are the most potent biological substances known to mankind. BoNTs are the agents responsible for botulism, a rare condition affecting the neuromuscular junction and causing a spectrum of diseases ranging from mild cranial nerve palsies to acute respiratory failure and death. BoNTs are a potential biowarfare threat and a public health hazard, since outbreaks of foodborne botulism are caused by the ingestion of preformed BoNTs in food. Currently, mathematical models relating to the hazards associated with C. botulinum, which are largely empirical, make major contributions to botulinum risk assessment. Evaluated using statistical techniques, these models simulate the response of the bacterium to environmental conditions. Though empirical models have been successfully incorporated into risk assessments to support food safety decision making, this process includes significant uncertainties so that relevant decision making is frequently conservative and inflexible. Progression involves encoding into the models cellular processes at a molecular level, especially the details of the genetic and molecular machinery. This addition drives the connection between biological mechanisms and botulism risk assessment and hazard management strategies. This review brings together elements currently described in the literature that will be useful in building quantitative models of C. botulinum neurotoxin production. Subsequently, it outlines how the established form of modeling could be extended to include these new elements. Ultimately, this can offer further contributions to risk assessments to support food safety decision making.     

Method for Estimating the Presence of Clostridium perfringens in Food

The methods currently used for the enumeration of Clostridium perfringens in food are often inadequate because of the rapid loss of viability of this organism when the sample is frozen or refrigerated. A method for estimating the presence of C. perfringens in food which utilizes the hemolytic and lecithinase activities of alpha toxin was developed. The hemolytic activity was measured in hemolysin indicator plates. Lecithinase activity of the extract was determined by the lecithovitellin test. Of 34 strains of C. perfringens associated with foodborne disease outbreaks, 32 produced sufficient alpha toxin in roast beef with gravy and in chicken broth to permit a reliable estimate of growth in these foods. Alpha toxin was extracted from food with 0.4 m saline buffered (at pH 8.0) with 0.05 mN-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid and concentrated by dialysis against 30% polyethylene glycol. A detectable quantity of alpha toxin was produced by approximately 10(6)C. perfringens cells per g of substrate, and the amount increased in proportion to the cell population. Results obtained with food samples responsible for gastroenteritis in humans indicate that a correlation can be made between the amount of alpha toxin present and previous growth of C. perfringens in food regardless of whether the organisms are viable when the examination is performed.     

A SIMPLE AND RAPID DETECTION BY PCR OF ENTEROPATHOGENIC ESCHERICHIA COLI IN NATURALLY CONTAMINATED VEGETABLES

Contaminated vegetables have been identified as one of the principal sources of foodborne illnesses. Escherichia coli is one of the bacteria that can contaminate vegetables and cause serious foodborne disease. The development of simple and rapid assays for detection of E. coli would enable official agencies and food industries to identify contaminated foodstuffs in a timelier manner. In this work, we detected E. coli contamination in four types of vegetables using a 24 h procedure. This method is very specific, rapid and simple to use in the laboratory. Indeed, the enrichment, DNA isolation and polymerase chain reaction (PCR) amplification procedures described here can also be used for detection of E. coli in other foods.

PRACTICAL APPLICATIONS

Foodborne disease remains an important public health threat worldwide; one of the most important food safety hazards is associated with raw vegetables. Several studies have found that products can support the growth of enteric bacterial pathogens such as Salmonella , Shigella and Escherichia coli . Culture techniques are universally recognized as the standard method for detecting pathogenic bacteria in foods. Bacteria are detected and subsequently identified by growth on solid selective culture media and by analysis of metabolic properties or serotyping. This process is lengthy and may last 5–10 days or more. In our investigation, the polymerase chain reaction (PCR) detection of E. coli in vegetables was realized within 24 h. The pre-enrichment step used in this study did not have any inhibiting effect on the PCR. Therefore, it became possible to rapidly and directly detect E. coli in raw vegetables by the PCR technique just by heating samples.     

Bacterial contaminants and their antibiotic susceptibility patterns in ready-to-eat foods vended in Ogun state,Nigeria

Contamination of ready-to-eat (RTE) foods by pathogenic bacteria may predispose consumers to foodborne diseases. This study investigated the presence of bacterial contaminants and their antibiotic susceptibility patterns in three locally processed RTE foods (eko, fufu and zobo) vended in urban markets in Ogun state, Nigeria. Bacteria isolated from a total of 120 RTE food samples were identified by 16S rRNA gene phylogeny while susceptibility patterns to eight classes of antibiotics were determined by the disc diffusion method. Species belonging to the genera Acinetobacter and Enterobacter were recovered from all RTE food types investigated, Klebsiella and Staphylococcus were recovered from eko and fufu samples, while those of Shigella were recovered from eko samples. Enterobacter hormaechei was the most prevalent species in all three RTE food types. Precisely 99% of 149 isolates were multidrug-resistant, suggesting a high risk for RTE food handlers and consumers. Co-resistance to ampicillin and cephalothin was the most frequently observed resistance phenotype. Results demonstrate that improved hygiene practices by food processors and vendors are urgently required during RTE processing and retail. Also, adequate food safety guidelines, regulation and enforcement by relevant government agencies are needed to improve the safety of RTE foods and ensure the protection of consumer health.     

Foodborne viruses

Foodborne and waterborne viral infections are increasingly recognized as causes of illness in humans. This increase is partly explained by changes in food processing and consumption patterns that lead to the worldwide availability of high-risk food. As a result, vast outbreaks may occur due to contamination of food by a single foodhandler or at a single source. Although there are numerous fecal-orally transmitted viruses, most reports of foodborne transmission describe infections with Norwalk-like caliciviruses (NLV) and hepatitis A virus (HAV), suggesting that these viruses are associated with the greatest risk of foodborne transmission. NLV and HAV can be transmitted from person to person, or indirectly via food, water, or fomites contaminated with virus-containing feces or vomit. People can be infected without showing symptoms. The high frequency of secondary cases of NLV illness and - to a lesser extent - of hepatitis A following a foodborne outbreak results in amplification of the problem. The burden of illness is highest in the elderly, and therefore is likely to increase due to the aging population. For HAV, the burden of illness may increase following hygienic control measures, due to a decreasing population of naturally immune individuals and a concurrent increase in the population at risk. Recent advances in the research of NLV and HAV have led to the development of molecular methods which can be used for molecular tracing of virus strains. These methods can be and have been used for the detection of common source outbreaks. While traditionally certain foods have been implicated in virus outbreaks, it is clear that almost any food item can be involved, provided it has been handled by an infected person. There are no established methods for detection of viruses in foods other than shellfish. Little information is available on disinfection and preventive measures specifically for these viruses. Studies addressing this issue are hampered by the lack of culture systems. As currently available routine monitoring systems exclusively focus on bacterial pathogens, efforts should be made to combine epidemiological and virological information for a combined laboratory-based rapid detection system for foodborne viruses. With better surveillance, including typing information, outbreaks of foodborne infections could be reported faster to prevent further spread.     

Does microbiological testing of foods and the food environment have a role in the control of foodborne disease in England and Wales?

This review looks at the contribution of microbiological sampling to the safety of retail foods in England and Wales. It compares sampling methods available and assesses the value of testing as part of outbreaks of foodborne disease, as part of routine management by local authorities, as part of work done or commissioned by the food industry, and as part of research. It confirms that microbiological testing has a role during outbreaks as it makes a significant contribution to help identify foods and other areas of greatest risk for future study. The review suggests that routine testing by local authorities is often of limited use and could be improved by more targeted surveillance. Testing could be better used to validate primary control methods, such as Hazard Analysis and Critical Control Point (HACCP) system. Any public health benefit from testing in the food industry is often restricted by client confidentiality. Microbial research on foods is important as it can lead to significant improvements in safety. Current microbiological methods are slow and, in future, rapid molecular methods may make an even bigger contribution to the control of foodborne disease.     

Electrochemiluminescent functional nucleic acids‐based sensors for food analysis

Foodborne contaminants widely exist in foods, which can lead to various foodborne diseases and food safety issues. The development of quick, sensitive and universal analytical approaches for foodborne contaminants is imperative. Electrochemiluminescent functional nucleic acids (ECL FNAs)‐based sensors are a series of sensing devices using FNAs as the recognition elements and ECL as the transducer. Contributing to the specific recognition ability of FNA and the high sensitivity of ECL, ECL FNA‐based sensors are considered to be of great application potential for foodborne contaminants monitoring. This review mainly presents the applications of ECL FNA‐based sensors for foodborne contaminants (including microorganisms, mycotoxins, allergens, antibiotics, heavy metal ions, pesticides and some illegal additives). In general, the application of ECL FNA‐based sensors in the field of food analysis is just in its infancy. Although there are several limitations and challenges, it is envisaged that ECL FNA‐based sensors will have broad prospects for food analysis in the future.     

Microbial diversity and prevalence of foodborne pathogens in cheap and junk foods consumed by primary schoolchildren

Aerobic plate counts (APC), coliforms, Bacillus cereus, Escherichia coli and eight foodborne pathogens were tested in 1008 cheap and junk foods, including candies, dried cakes, chewing gum, chocolate, dried and seasoned seafood, ice cream, and sugary foods. APCs were positive for 342 samples (33·9%), and the majority of the counts were 2–3 log CFU g^?1 or ml^?1 (average: 1·10 log CFU g^?1 or ml^?1). Most samples (97·3%) contained no coliforms (average: 0·07 log CFU g^?1 or ml^?1). Bacillus cereus was detected in 68 samples (average: 0·14 log CFU g^?1 or ml^?1). Escherichia coli and Listeria monocytogenes were detected in 6 and 1 samples, respectively, whereas other foodborne pathogens were not isolated. The highest bacterial counts were associated with dried and seasoned seafood products and dried cakes, suggesting that appropriate regulations of these food types should be considered. Cheap and junk foods were produced mainly in developing countries, but there were no significant differences in the bacterial counts among different countries of origin. The presence of foodborne pathogens may pose a risk for children. These results suggest that there is cause for deeper concern about the safety of these foods and that effective countermeasures should be established to improve their microbiological safety.

Significance and Impact of the Study

Food safety is especially important for children, but only limited information is available about the microbiological quality of cheap and junk foods that are consumed frequently by primary schoolchildren (e.g. dried cakes, candies and chocolates). The present study investigated the microbial quality of cheap and junk foods, and our results indicate that these foods are a potential health risk for children, therefore, deeper concern about the safety of these foods and effective countermeasures should be established to improve their microbiological safety. The present study may contribute to the development of an appropriate child food safety management system.     

食源性致病菌多重分子生物学检测技术研究进展

快速、可靠的食源性致病菌高通量检测方法对于确保食品安全具有重要意义,近年基于DNA水平的多重分子生物学检测技术迅速发展,针对各种不同的食源性致病菌建立了多种多重分子检测技术,包括多重PCR、多重实时荧光PCR以及基因芯片等。对这些多重分子检测技术的最新研究进展作一综述,并且建议在今后该技术的研究中,仍需要在食品中多种致病菌同时选择性增菌培养、亚致死损伤修复以及检测内标的构建等方面取得突破,从而能够更好地实现食源性致病菌的高通量检测。     

Techno-economic analysis of a plant-based platform for manufacturing antimicrobial proteins for food safety

Continuous reports of foodborne illnesses worldwide and the prevalence of antibiotic-resistant bacteria mandate novel interventions to assure the safety of our food. Treatment of a variety of foods with bacteriophage-derived lysins and bacteriocin-class antimicrobial proteins has been shown to protect against high-risk pathogens at multiple intervention points along the food supply chain. The most significant barrier to the adoption of antimicrobial proteins as a food safety intervention by the food industry is the high production cost using current fermentation-based approaches. Recently, plants have been shown to produce antimicrobial proteins with accumulation as high as 3 g/kg fresh weight and with demonstrated activity against major foodborne pathogens. To investigate potential economic advantages and scalability of this novel platform, we evaluated a highly efficient transgenic plant-based production process. A detailed process simulation model was developed to help identify economic “hot spots” for research and development focus including process operating parameters, unit operations, consumables, and/or raw materials that have the most significant impact on production costs. Our analyses indicate that the unit production cost of antimicrobial proteins in plants at commercial scale for three scenarios is $3.00–6.88/g, which can support a competitive selling price to traditional food safety treatments.     

PermaBN: A Bayesian Network framework to help predict permafrost thaw in the Arctic

Rising global temperatures are a threat to the current state of the Arctic. In particular, permafrost degradation has been impacting the terrestrial cryosphere in many ways, including effects on carbon cycling and the global climate, regional hydrological connectivity and ecosystem dynamics, as well as human health and infrastructure. However, the ability to simulate permafrost dynamics under future climate projections is limited, and model outputs are often associated with large uncertainties. A model structured on a Bayesian Network is presented to address existing limitations in the representation of physically complex processes and the limited availability of observational data. A strength of Bayesian methods over more traditional modeling methods is the ability to integrate various types of evidence (i.e., observations, model outputs, expert assessments) into a single model by mapping the evidence into probability distributions. Here, we outline PermaBN, a new modeling framework, to simulate permafrost thaw in the continuous permafrost region of the Arctic. Pre-validation and expert assessment validation results show that the model produces estimations of permafrost thaw depth that are consistent with current research, i.e., thaw depth increases during the snow-free season under initial conditions favoring warming temperatures, lowered soil moisture conditions, and low active layer ice content. Using a case study from northwestern Canada to evaluate PermaBN, we show that model performance is enhanced when certainty about the system components increases for known scenarios described by observations directly integrated into the model; in this case, insulation properties from vegetation were integrated to the model. Overall, PermaBN could provide informative predictions about permafrost dynamics without high computational cost and with the ability to integrate multiple types of evidence that traditional physics-based models sometimes do not account for, allowing PermaBN to be applied to carbon modeling studies, infrastructure hazard assessments, and policy decisions aimed at mitigation of, and adaptation to, permafrost degradation.     

Assessment of the food safety issues related to genetically modified foods

International consensus has been reached on the principles regarding evaluation of the food safety of genetically modified plants. The concept of substantial equivalence has been developed as part of a safety evaluation framework, based on the idea that existing foods can serve as a basis for comparing the properties of genetically modified foods with the appropriate counterpart. Application of the concept is not a safety assessment per se, but helps to identify similarities and differences between the existing food and the new product, which are then subject to further toxicological investigation. Substantial equivalence is a starting point in the safety evaluation, rather than an endpoint of the assessment. Consensus on practical application of the principle should be further elaborated. Experiences with the safety testing of newly inserted proteins and of whole genetically modified foods are reviewed, and limitations of current test methodologies are discussed. The development and validation of new profiling methods such as DNA microarray technology, proteomics, and metabolomics for the identification and characterization of unintended effects, which may occur as a result of the genetic modification, is recommended. The assessment of the allergenicity of newly inserted proteins and of marker genes is discussed. An issue that will gain importance in the near future is that of post-marketing surveillance of the foods derived from genetically modified crops. It is concluded, among others that, that application of the principle of substantial equivalence has proven adequate, and that no alternative adequate safety assessment strategies are available.     

Prevalence and expression of enterotoxins in Bacillus cereus and other Bacillus spp., a literature review

Members of the Bacillus genus are ubiquitous soil microorganisms and are generally considered harmless contaminants. However, a few species are known toxin producers, including the foodborne pathogen, B. cereus. This species produces two distinct types of foodborne illness, the emetic (vomit-inducing) syndrome, associated with consumption of toxin in cooked rice dishes, and the diarrheal illness seen occasionally following consumption of contaminated meats, sauces, and certain dairy products. In the latter case, illness results from the production of enterotoxins by vegetative cells in the small intestine of the host. In dairy products, the occurrence of Bacillus spp. is inevitable, and the spore-forming ability of this organism allows it to easily survive pasteurization. Many strains have been shown to grow and produce enterotoxin in dairy products at refrigeration temperatures. Evaluation of toxin gene presence and toxin expression in Bacillus spp. other than B. cereus has not been thoroughly investigated. However, the presence of natural isolates of Bacillus spp. harboring one or more enterotoxin gene(s) and subsequent demonstration of conditions which may support toxin expression holds crucial importance in the food safety arena.     

Regulatory Agencies and Food Safety

Prior to Confederation, food control legislation in Canada consisted of only a few simple laws governing the quality, grading, packing and inspection of certain staple foods. The Inland Revenue Act of 1875 provided the first real control in Canada over adulteration of liquor, foods and drugs. Since then, food legislation has evolved in scope and complexity as the industries involved have developed, as consumers have become better informed, and as scientific advances have provided a sound basis for regulations. Present regulations under the Food and Drugs Act are intended to give consumers broad protection against health hazards and fraud in the production, manufacture, labelling, packaging, advertising, and sale of foods. This principle is well illustrated by present requirements for the control of pesticide residues, chemical additives, and the addition of vitamins to foods. In today''s era of rapid technological change, application of current scientific knowledge to the food industry obviously involves the possibility of hazards to health. Regulatory agencies with responsibility for food safety must, therefore, fully utilize scientific knowledge in order to reduce the risks involved to a minimum.     

Occupational exposures and reproductive health: 2003 Teratology Society Meeting Symposium summary

Assuring reproductive health in the workplace challenges researchers, occupational safety and health practitioners, and clinicians. Most chemicals in the workplace have not been evaluated for reproductive toxicity. Although occupational exposure limits are established to protect 'nearly all' workers, there is little research that characterizes reproductive hazards. For researchers, improvements in epidemiologic design and exposure assessment methods are needed to conduct adequate reproductive studies. Occupational safety and health programs' qualitative and quantitative evaluations of the workplace for reproductive hazards may differ from standardized approaches used for other occupational hazards in that estimates of exposure intensity must be considered in the context of the time-dependent windows of reproductive susceptibility. Clinicians and counselors should place the risk estimate into context by emphasizing the limitations of the available knowledge and the qualitative nature of the exposure estimates, as well as what is known about other non-occupational risk factors for adverse outcomes. This will allow informed decision-making about the need for added protections or alternative duty assignment when a hazard cannot be eliminated. These policies should preserve a worker's income, benefits, and seniority. Applying hazard control technologies and hazard communication training can minimize a worker's risk. Chemical reproductive hazard training is required for workers by the Occupational Safety and Health Administration's Hazard Communication Standard. The National Institute for Occupational Safety and Health (NIOSH) has formed a National Occupational Research Agenda Team to promote communication and partnering among reproductive toxicologists, clinicians and epidemiologists, to improve reproductive hazard exposure assessment and management, and to encourage needed research.     

From soil to gut: Bacillus cereus and its food poisoning toxins

Bacillus cereus is widespread in nature and frequently isolated from soil and growing plants, but it is also well adapted for growth in the intestinal tract of insects and mammals. From these habitats it is easily spread to foods, where it may cause an emetic or a diarrhoeal type of food-associated illness that is becoming increasingly important in the industrialized world. The emetic disease is a food intoxication caused by cereulide, a small ring-formed dodecadepsipeptide. Similar to the virulence determinants that distinguish Bacillus thuringiensis and Bacillus anthracis from B. cereus, the genetic determinants of cereulide are plasmid-borne. The diarrhoeal syndrome of B. cereus is an infection caused by vegetative cells, ingested as viable cells or spores, thought to produce protein enterotoxins in the small intestine. Three pore-forming cytotoxins have been associated with diarrhoeal disease: haemolysin BL (Hbl), nonhaemolytic enterotoxin (Nhe) and cytotoxin K. Hbl and Nhe are homologous three-component toxins, which appear to be related to the monooligomeric toxin cytolysin A found in Escherichia coli. This review will focus on the toxins associated with foodborne diseases frequently caused by B. cereus. The disease characteristics are described, and recent findings regarding the associated toxins are discussed, as well as the present knowledge on virulence regulation.     

Listeria monocytogenes’ Step-Like Response to Sub-Lethal Concentrations of Nisin

Microbial safety of food products is often accomplished by the formulation of food-grade preservatives into the product. Because of the growing consumer demand for natural substances (including preservatives) in the composition of consumed foods, there is also a growing interest in the natural antimicrobial nisin, which has generally recognized as safe (GRAS) status for certain applications. During the products storage time, concentrations of preservative(s) are decreasing, which may eventually cause a serious problem in the food’s microbial safety. Here, for the first time we report on the non-linear response of a foodborne pathogen, Listeria monocytogenes, to sub-lethal concentrations of nisin.     

Comparing Injury and Illness Risk Assessments for Occupational Hazards

One common framework for describing the evaluation and assessment of hazards in the workplace includes the four steps of hazard identification, exposure assessment, exposure-response modeling, and risk characterization (NAS, 1983). We discuss hazards for occupational injury and illness in light of this framework, and we contrast the evaluation of injury hazards with the evaluation of illness hazards. In particular, the nature of the hazards, typical exposure patterns, quantification of exposure, and the attribution of outcome to exposure are discussed. Finally, we discuss the management of occupational illness and injury hazards and issues encountered when evaluating efforts designed to mitigate the effects of occupational hazards.