Paralytic Shellfish Toxins Are Naturally Occurring Toxins

Essay add: 22-10-2015, 20:34   /   Views: 95

A Bacterial spore (endospore) is a bacterium that has formed a thick outer wall to be able to survive in extreme environmental conditions, that it wouldn't normally live in. Some of these conditions include high temperatures, dryness, toxic chemicals ...etc. Once the endospore is formed, the vegetative portion of the bacterium is degraded and the dormant endospore is released. The endospore is able to survive for long periods of time until environmental conditions again become favorable for growth. Bacterial spores are common contaminants of food products, and their outgrowth may cause food spoilage or foodborne illnesses.

Because foods undergo certain processing and preparation such as heat, freezing, and chemicals, bacterial spores are a hazard. Although the vegetative cell is killed by these conditions, the spores can survive and need harsher conditions to be inactivated, which are costly and detrimental to the nutritional and organoleptic quality of most food products.Paralytic shellfish toxins are naturally occurring toxins, called "saxitoxins" STX, also referred to as PSP toxins (PST), these are produced by some species of microalgae, especially Gonyaulacoid dinoflagelletes. Shellfish are filter feeders so when they pump water through their systems, they filter out algae and other food particles for food, they eat toxin-producing algae, and so the toxin can accumulate in their tissue. When ingested by humans, tingling sensation in the lips and finger tips is the first symptoms.

High toxin levels causes muscle paralysis, severe illness and even death. Regarding the significance, Gastrointestinal and neurologic symptoms are caused predominantly by the consumption of contaminated shellfish, contaminated products such as supplements. Food microbiologists have used the mouse bioassay for a long time for examining shellfish (especially for PSP). Recently a High Performance Liquid Chromatography (HPLC), has been developed to identify individual PSP toxins (saxitoxin = 20 fg/100 g of meats; 0.2 ppm).Microbial injury happens to microbial cells when they lose some of their distinctive qualities but survive stress.

Injured microbial cells can form colonies on non-selective media, but not on selective media. Regarding the significance to food microbiology, the existence of injured microorganisms in food and their recovery during culturing procedures is critical. Injured microorganisms present a potential threat in food safety since they may repair themselves under suitable conditions. Detection of injured microorganisms can be important to practical interpretations of data in food microbiology. Microbial contamination of food is a major concern for the food industry, regulatory agencies and consumers.

The ability to detect foodborne pathogens is critical for final products that have undergone food processing. A good method should detect both normal and injured microorganisms. Injured organisms are as important as normal microorganisms because they can resuscitate and function normally in the presence of the selective agent and regain its ability to form a colony.Intrinsic factors are Inherent properties of the food itself when considering foods.

Intrinsic factors are requirements which by nature are necessary to the microorganism when considering microbes. So we could say that microorganisms depend on their requirements in foods. The nutritional requirement, a growth-limiting factor that bacteria need, such as vitamins, minerals, amino acids…etc. So depending on the food characteristics, microorganisms will do different actions.

Food spoilage, for example is a result of intrinsic factors. Regarding their importance in food microbiology, the following common intrinsic factors affect the growth and multiplication of microorganisms in foods pH, moisture and nutrient content. Food such as carbohydrates, fats and proteins are made up of organic compounds, whose nutrition attract microbes are more prone to spoilage while vitamins and minerals are not and so are good for a longer time.Biofilm forms when communities of microbial cells grow on living or inert surfaces densely compact surrounding themselves with secreted polymers. Many bacterial species form these coordinated and cooperative groups, similar to multicellular organisms. Biofilms survive the unpredictable environmental stressors on food surfaces such as temperature changes, desiccation, ultraviolet rays, etc.

Network of cell-to-cell communication-quorum sensing-enhances biofilms' access to nutrients and favorable environments. Researchers have estimated that 60-80%of microbial infections are caused by bacteria growing as a biofilm compared to free-floating bacteria (planktonic). Foodborne illnesses associated with fresh produce have risen dramatically over the past 30 years. In fact, up to 80% of bacteria on produce surfaces constitute biofilms.Human Norovirus (NoV), members of the Caliciviridae family is a very enteric contagious virus, able to survive outside the host and to remain relatively stable under food processing and storage conditions. In fact, any type of food product is a potential vehicle for NoV transmission and can cause infection with only a few infectious NoV particles.

Food microbiologists examine people who work with food; epidemiological investigation of outbreaks has shown that more than 67% of all food-borne disease outbreaks due to known agents are caused by NoV. These viruses are transmitted mainly by person-to-person contact or by consumption of food or water contaminated directly by fecal matter or vomitus or indirectly by exposure to contaminated surfaces. However, the consumption of fresh produce and ready-to-eat food contaminated by ill or asymptomatic food handlers has been identified as the most common source of NoV outbreaks.

People get infected when they touch surfaces that have stool or vomit that has the virus within it or by vomit particles in the air (aerosol) that are near an infected area.Q2.Bacillus cereus food poisoning was first published in 1950. The first documented outbreak in the US was in 1969 and the first one in the UK was in 1971. Bacillus cereus forms bacterial spores within the soil it inhabits, but does not have a known animal habitation. It can grow with the presence of oxygen or with no oxygen. It is highly heat-resistant and can withstand any kinds of preparation's that use heat in the domestic kitchen.

But it cannot withstand the temperatures used in food processing facilities when making canned foods. The Bacillus cereus has two different strains each produces a different toxin than the other, so depending on the strain, two syndromes are possible. One of the strains contains a heat-stable emetic toxin which is made by the microbe in food that it grows in causing a rapid onset emetic syndrome.

On the other hand the second strain produces a heat-sensitive enterotoxin in food and also in the intestines, which causes intestinal upset known as diarrheic syndrome. The onset of this strain is slow and can start sometimes from 8 to 16 hours after consumption. Consumption of contaminated food with the emetic toxin generates nausea and vomiting that starts as rapid as 30 minutes after consumption.Recent outbreaks caused by this pathogen that have made the headlines include the fatal family outbreak associated with food Poisoning in August 2003. Five children fell sick to the illness after consuming pasta salad. Approximately after 6 hours of the meal the youngest started vomiting.

She was taken to the nearby hospital emergency room after she complained of having respiratory problems. As the family arrived at the hospital, the rest of the children started vomiting too. All children had different severity of symptoms and needed immediate medical attention in a bigger and more convenient hospital.

They were taken to the University Hospital in Leuven. As they were transferring the children to the hospital the youngest fell into a coma because of her severe pulmonary hemorrhage and so she needed continuous resuscitation. After their arrival for about twenty minutes she was pronounced dead as a result of diffusive bleeding, and severe muscle cramps. An autopsy was carried out and Bacillus cereus was found in the contents of her gut. Her spleen was also infected, most likely by the translocation of bacteria after she had died.

Her liver had microvascular and extensive coagulation necrosis and also showed metabolic acidosis and liver failure. The older boy was also affected severely by the bacteria, although his symptoms were lighter than his younger sister. He was moved to the pediatric intensive care unit, where he was put on a mechanical ventilation and invasive hemodynamic observation.

His blood lactate levels decreased slowly after he underwent fluid resuscitation. The rest of the children had mild symptoms and recovered fully quickly.Another major outbreak in another part of the world was between 3rd and 5th of May 2008 in Oman. Fifty eight people were reported sick with gastroenteritis in a referral hospital. Patients and their attendants were among the reported cases. They all had consumed meals at the hospital the prior day.

An investigation team interviewed the patients and their attendants about their symptoms and what they had eaten the previous day while they were in the hospital. Samples were taken from the food in the kitchen and kitchen staff fecal matter was also sampled and those affected and then these were cultured. A kitchen environmental assessment was conducted.

The majority of those affected were adult females, mainly patient attendants. The symptoms among those infected were mainly diarrhea and little vomiting. Most of them had mild symptoms and so needed mild medication and little attention except for two patient attendants who needed intravenous rehydration. The staff had violated many of the basic food hygiene protocols in the kitchen. B. cereus was detected in 25 % of patients and 76% of kitchen staff, and 57% of the kitchen food samples.Bacillus cereus colonies are isolated by the presence of lecithinase, an enzyme found in B. cereus on MEP agar.

A halo appears because of the insoluble lipids released by the action of lecithinase. They can also be isolated by their incapability of fermenting mannitol with the appearance of a pink color as a result of an increase in pH, the phenol red turns pink. When using a blood agar, clear zones appear as a result of Beta-hemolysis of the red blood cells. The ability to lyse red blood cells resembles toxin production in B. cereus strains.

Consequent immunological detection of Bacillus cereus toxin is done by removing the nitrocellulose membrane in blood agar plates, as the nitrocellulose membrane starts to appear, indicates the presence of the B. cereus toxins. Detecting bacillus cereus can be done by PCR and the Tecra VIA. B. cereus contains three genes nheA, nheB, and nheC, encoding the nonhemolytic enterotoxin. So depending on these genes, detection of the different strains can be accomplished. The nheA gene was not detected by PCR, although it can be by the Tecra VIA.

This is most likely due to sequence differences among the nheA genes of certain strains. Five different sets of primers are used for PCR-based detection of the bceT gene inferred from the B. cereus B-4ac sequence. B. cereus strains yield PCR products with sizes that correspond to the PCR products of B. cereus B-4ac. The Southern analysis detects all B. cereus strains that are PCR positive with primer sets 113 and/or 114 and not PCR negative strains for all primer sets.Factors that affect the growth and survival of B. cereus include higher temperatures and high water activity (aw) values.

Its temperature range is from 10-49°C and its optimum temperature is 30°C. A temperature increase from 90 to 95 C has a large impact on the inactivation of the bacteria's spores. B. cereus can grow in a pH range of 4.9-9.3, but any pH lower than 4.9 and higher than 9.3 is detrimental to its growth. The lowest reported water activity level for B. cereus growth is 0.93; anything lower will not provide the appropriate free water available for its growth.

So for example B. cereus spores in paprika powder could be reduced by 4.5 log10 CFU/g within 6 min at an aw value of 0.88 and heated to product temperatures of 95-100 C. Lowering pH does not result in a significant reduction in the concentration of B. cereus spores.B. cereus is transmitted to foods mostly by cross contamination or if that food has not been cooked to a high enough temperature. Bacillus cereus is a common soil inhabitant that is found mostly on harvested crops such as grains, vegetables and fruits. Illnesses are most likely to be associated with ingesting foods that have not been cooked to a temperature that destroys the spores that are heat-resistant or refrigerated not as quick as needed and left out at room temperature.Common sources include Soil, unpasteurized milk, cereals and starch, Herbs and spices as I had mentioned before, a spice example (papirika) was mentioned in the "factors that affect B. cereus" section.

Associated foods include meat pies, cooked rice and fried rice, starchy foods (potato, pasta), food mixtures (soups, casseroles, sauces) and puddings.According to the type of illness symptoms are different, diarrheal illness and vomiting illness express different symptoms. The diarrheal illness includes watery diarrhea, abdominal pain and cramps, nausea and rarely vomiting. These symptoms usually last 24 hours.

The vomiting illness usually lasts less than 24 hours and is characterized by nausea and vomiting. Occasionally abdominal pain and diarrhea may occur. This illness is sometimes mistaken for an illness caused by Staphylococcus aureus. The vomiting illness is also known as the Emetic syndrome. The onset of its symptoms starts within about 1 to 5 hours after consumption of the contaminated food, and the duration of the symptoms is 24 hours at most.

It is a bout of nausea and vomiting. The onset of symptoms of the Diarrheic syndrome starts within 8 to 12 hours after consumption of the contaminated food, and the symptoms last also 24 hours at most. The iinfective dose is a large numbers (more than 105 CFU/gm) of viable Bacillus cereus cells need to be consumed for symptoms of the illness to develop.The pathogenic mechanisms of the emetic form of disease are not well understood. After the food contaminated with the bacteria is ingested, the bacteria forms toxins that it requires for its survival. This form is mainly caused when consumption of inappropriately refrigerated rice that had not been cooked at a sufficient temperature and time appropriate to kill the B. cereus spores.

Soon spores start to produce a toxin to survive on called cereulide. This toxin is made while the food is refrigerating but does not get destroyed if later heating was used. A person then consumes the rice and soon experiences nausea and vomiting within 1-5 hours after eating. These symptoms are mistaken sometimes for Staphylococcus aureus symptoms. There is little known about this mechanism pathway and further research is required.

Sometimes the toxins enter the blood stream and interact with the Vagus nerve leading to emesis ( just as the first outbreak I mentioned). Regarding the mechanism pathway for the diarrheic form of the illness, four enterotoxins are produced by Bacillus cereus, hemolysin BL (HBL), nonhemolytic enterotoxin (NHE), enterotoxin-T and cytotoxin-K, as previously mentioned. The HBL, NHE, and cytotoxin-K are related to food poisoning outbreaks. HBL and NHE are very similar, they are vegetative growth metabolites. Research has proven that HBL and NHE do not play a role in the pathogenicity of B. cereus when they are produced in the food.

Furthermore, the majority of the vegetative cells of B. cereus also do not cause pathogenicity of B. cereus. In most cases the pH in the stomach is too low for vegetative cells to survive. However, consumption of different foods alters the pH in the stomach, even though the pH is mainly low it may get higher enabling the bacteria to survive and even grow. And so, spores are able to survive and enter the intestines with the chyme.

As the spores are in the small intestine, they germinate, grow and simulate the production of enterotoxins. This is believed to be the route for the diarrheal syndrome caused by B. cereus. The spores are able to adhere to the intestines epithelial cells.Prevention is a major key that benefits a community when outbreaks are nearby. Consumers should pay attention to food recalls and as soon as there is an active recall get rid of any recalled food. Refrigerating cooked foods as soon as there is no need for them will minimize the possibility of emetic illness (cool cooked products to 41°F within 4 hours).

Food that is cooked and then frozen should be thawed inside the refrigerator to prevent any contamination that would occur if food was thawed at room temperature. Foods should be stored at sufficient temperatures. Infants should not be fed formula that has been sitting out at room temperature. Produce should be washed thoroughly and handled well. Hands should be washed always before and after handling produce and any other foods I mentioned that were associated with B. cereus.

Ground meat products should be thoroughly cooked.Further research: Improved knowledge of the pathogenic mechanism for the emetic form of B. cereus is necessary for two reasons. Firstly, better understanding of the pathogenic mechanism may lead to a better description of the dose-response relationship in humans. Secondly, a better insight into the pathogenic mechanism in combination with quantitative data concerning the occurrence of pathogenic B. cereus may lead to adjusting the tolerance level set for B. cereus in food commodities.Using homogenizing sterilizer, which mixes heated layers of powdery foods intensively, is a good method of destroying B. cereus bacteria and spores.

Also Using high dry heat temperatures have proven to be a good method of destroying B. cereus while it's in foodsQ3.The main issue for fresh produce, ready-to-eat and easy-to-prepare foods producers is maintaining and improving their foods safety from the source farm to the consumer's plate. Fresh fruits and vegetables are often thought to be healthy and nutritious, while ready-to- prepare foods are thought to be efficient and easy-to- prepare are thought to be less consuming. People are eating more of these less time consuming products to save time for their daily routines. The average consumer thinks that these rarely have risks of foodborne illnesses, but this is changing with the increase of foodborne illness outbreaks.

Food workers and retailers have started to reevaluate the production and handling practices of these foods as a result of this increase in outbreaks. The probability of getting sick from eating these foods is very low, but this small probability does exist. So reducing the risk of getting a foodborne illness is a concern to everyone, including food production workers in the different areas and the consumer too.

The major food that is causing the most outbreaks is fresh fruits and vegetables and also minimally processed vegetables. These have been the most recent sources of food poisonings and outbreaks.Produce that includes fruits, vegetables and fresh herbs are currently the greatest concern in terms of microbiological hazards because of the enteric bacteria, foodborne viruses or protozoa that it may possess. These are the main hazards in fresh produce that pose risks on human health the marketing economy.

Leafy green vegetables and fresh herbs are considered the major contaminated produce forms. Annually the USDA the United States department of Agriculture in the US and the Rapid Alert System for Food and Feed (RASFF) in the EU receive multiple alerts on the detection of pathogenic microorganisms in fruits and vegetables that may potentially pose a risk to the consumer. These alerts are incentives to identify, monitor and estimate risks and risk factors associated with microbial hazards in the fresh produce chain. The spinach E. coli O157:H7 outbreak in 2006 that affected 25 states happened in September 2006 and later in December the source of the outbreak was a spinach growers farm that was previously used by an angus cattle ranch.

In one study at least 276 consumer illnesses and 5 deaths were reported. Some studies reported 204 confirmed cases in 26 states and 1 confirmed case in one Canadian province. There were 104 hospitalizations, 31 Hemolytic Uremic Syndrome cases, 3 deaths.

On October 5, 2006 an Idaho Toddler was killed as a result of consuming the tainted spinach.Foodborne pathogens may be present in the feces of asymptomatic wild and domesticated animals. Therefore, any animal near produce and herb production spaces should are considered a hazard. Produce contamination can also be due to livestock wastes and their use on fields. Fertilizing with animal manures, humans and bio-wastes is an efficient provided they are properly composted and applied. Farm workers and farm gear can be considered as a contamination source.

All of these sources can harbor microbiological microbes that are just waiting to be transported to a food and then to a person's plate. The most frequently identified risk factors in leafy green associated outbreaks are water, wildlife, workers, and manure. This outbreak led to Canadian trade restrictions on USA-grown spinach for several months, and a recall of imported spinach in Canada. The harmful longer-term economic and health consequences were apparent when a year after the event, demand for spinach was still down by over 40% approximately. So according to this consequence the USDA and ERS have stated that leafy green vegetables from a worldwide viewpoint is considered the most important in terms of fresh produce safety.During the weeks that followed, an epidemiologic study was done to obtain information.

Soon the examination started to focus on a single lot code (P227) of the brand name "Dole" of baby spinach that was manufactured by Natural Selections Foods. After three weeks from the start of the investigation, the team investigators determined that four farms had supplied spinach for this same lot code. Soon investigations were initiated on these four farms.

The investigation collected to date, 800 Environmental Samples by the California Food Emergency Response Team. These samples were from water, soil/sediment, cow and wild pig feces, field product, finished product. Preliminary results were that E.coli O157:H7 positive samples found on all 4 ranches, 9 of these samples from one ranch are a PFGE match with the outbreak strain (1 = water, 1 = wild pig feces, 7 = cow feces). It was on October 12, 2006 that the E. coli strain from the contaminated spinach was linked to a California cattle ranch.

It was this day that the source of the deadly E. coli was found.Materials used in packagingModified atmosphere (MAP) chambers are used to preserve produce while they are transported. Mainly the oxygen levels are kept low while the carbon dioxide levels are raised to keep pathogens minimally active as possible. Fruits and vegetables are kept in MAP at a recommended O2 percentage of 1 and 5% for both safety and quality. Foodborne pathogens which may be resistant to moderate to high levels of CO2 (< 50%) is a major concern when using MAP. Permeable films promote spoilage before even toxin production starts, so MAP of produce, should always include packing materials that will not lead to an anoxic package environment when the product is stored at the anticipated temperature.

Fresh produce spoilage is caused by the background microflora and can be different from product to product and also storage conditions make a difference. MAP systems edible films are being researched in the meantime. However, there is a problem, the atmosphere can have too little O2 and then anaerobic pathogens such as C. botulinum can grow and survive.

Also antimicrobial compounds that can be added to the films are being studied. Problems such as antimicrobials leaking from the coatings previously tested to the foods have been studied and some of these compounds is sodium benzoate, benzoic acid, propionic acid, and potassium sorbate. Controlling organoleptic quality of fruit or vegetable product these processes is dependent on temperature control.

Optimum temperatures need to be maintained along the entire food production line, during processing, storing, shipping and selling. Maintaining sufficient storage temperatures is most difficult at the selling sites. Major microbes of concern regarding this problem include psychrotrophic microorganisms such as Y. entercolitica, non-proteolytic, C. botulinum, A. hydrophila and L. monocytogenes. Other microorganisms found in MAP, include E. coli O157:H7, Shigella spp and Salmonella spp. Sodium hypochlorite can be replaced with electrolyzed water to control microbial activity in food products.FAO, WHO and Codex recommendation's:Assess changes in consumption and production patterns.

Consumers tend to change their patterns towards food, say they used to cook their vegetables but then they are eating them raw. This has to be considered because changes in food patterns may be different than the way that foods should be handled and thus the way they are manufactured may have to change. Using risk assessment approaches to characterize the risks of food contamination and to assess the impact of controls. When possible, quantitative risk assessment should be done .But when they are not, qualitative risk assessment methods should be conducted.

Monitoring, preventing and controlling these microbiological hazards while in the fresh produce production process is a priority. It is known that controlling wild animals is difficult, but mitigation strategies to deter or discourage wildlife near produce fields maybe an option. Knowing the prior use of land by doing a risk assessment to the land before planting and cultivating new crops is done.

Before massive planting takes place a risk assessment on the microbiological contamination of leafy vegetables and herbs during the growing phase from that particular part of land should be done. This assessment should consider the impact of climate, topology, weather, hydrology and geographical features on the plants. Close by environmental sources should be put into mind because that could lead to cross-contamination.

A good land choice shouldn't be prone to flooding during the growing season. When say for example flooding does occur and fearing contamination, a risk assessment should be done to make measures that will reduce the risk of pathogens. If the damage is severe then the produce should be disposed of and never sold. Water and sewage units operated by farms such as wells, septic systems and water and sewage treatment systems should be capable of operating safely and effectively during periods of excessive rainfall. Nearby produce areas should be protected from fecal contamination.Because the average consumer considers leafy vegetables and herbs ready-to-eat products, it is that the produce be as clean as possible by using water that is fit to drink for harvesting, packaging and processing.

Groundwater and surface water resources should be checked prior to use and decontaminated if necessary. These should also be protected from pollution. In the case when there are not enough water supplies, abstracting water may be considered but making sure the sediments do not get disturbed. Disturbing sediments can help pathogens settle and survive in large numbers in the pores that have formed in the soil.

After the produce is harvested, handling should be taken seriously because now the effectiveness of eliminate foodborne pathogens from leafy vegetables and herbs is very low (this is before any cooking or heat is used). Temperature is the major factor in bacterial growth and survival conditions, so keeping produce at an undesirable temperature for the pathogens minimizes their growth and survival rates. This emphasizes the temperature control and maintenance needed in cold chain conditions to keep foods safe.

Educating and training factory workers about cold chain maintenance and informing them about advanced knowledge and technologies for both refrigeration and temperature monitoring are a key requirement in food safety. If hygiene guidelines are practiced poorly then field workers, food workers may be a major source of contamination. So it is important produce production areas be restricted only to necessary workers for its different areas of harvesting, processing and packaging.

Awareness among all workers in the factory should be stressed regarding taking all the precautionary necessary guidelines associated with fresh produce production. Food safety education interventions should be done to better educate the population about handling produce, whether ready-to-eat or whole. Further research is needed that can show how pre-harvest and postharvest practices of leafy vegetables and herbs lead to the contamination of produce.Organic food studies have shown that there are perceived benefits to the environment, animal welfare, and worker safety.

The main reason why consumers purchase organic foods is that they think that organic foods are safer and more nutritious. The differences between organic foods and inorganic foods with respect to food safety and nutrition is that organic fruits and vegetables have less pesticide deposits and low nitrate levels than do inorganic fruits and vegetables. But on the other hand, organic foods might have greater levels of plant secondary metabolites; although they may act as antioxidant compounds, but they contribute to naturally occurring toxins. Some research has shown that microbiological hazards are greater organic products due as a result of prohibiting antimicrobial use. It is too soon to dictate which of these foods is superior to the other with respect to safety or nutritional composition.

Both have their advantages and disadvantages, it just depends on whether you require a food that has less chemicals and more natural toxins (organic) or one that has less microbes and more chemical residues (inorganic).

Article name: Paralytic Shellfish Toxins Are Naturally Occurring Toxins essay, research paper, dissertation