All About Bacteria
All microorganisms can be divided into the following classes:
They all share one thing in common: they want to live and given the proper conditions they will start multiplying. They don’t grow bigger, they just divide and divide and divide until there is nothing for them to eat, or until conditions become so unfavorable that they stop multiplying and die. Meat contains about 75% of water and this moisture is the main reason that it spoils.
Bacteria love temperatures that revolve around the temperature of our body (36.6º C, 98.6º F). Holding products at higher temperatures (greater than 130º F, 54º C) restricts the growth of bacteria. Increasing temperatures over 60º C (140º F) will start killing them. Most bacteria need oxygen (aerobic), others thrive without it (anaerobic). All of them hate cold, and around 32º F, (0º C) they become lethargic and dormant when the temperature drops lower. Keeping them at low temperatures does not kill them, but only stops them from multiplying. Once when the conditions are favorable again, they will wake up and start growing again.
Some bacteria tolerate the presence of salt better than others and we take advantage of this when curing meats. Other bacteria (e.g. Clostridium botulinum) are able to survive high temperatures because they form spores. Spores are special cells that envelop themselves in a protective shell and become resistant to harsh environmental conditions. Once conditions become favorable, the cells return to their actively growing state.
Given favorable conditions bacteria can double up in numbers every 20 minutes. In a refrigerator their number will also grow, albeit at a reduced pace, but they can double up in 12 hours. Short of deep freezing, it is impossible to stop bacteria from contaminating meat, but we can create conditions that will slow down their growing rate. At room temperatures bacteria will grow anywhere they have access to nutrients and water. Microorganisms which are of special interest when processing meats:
- Food spoilage bacteria.
- Dangerous (pathogenic) bacteria.
- Beneficial bacteria.
- Yeasts and molds.
Food Spoilage Bacteria
Spoilage bacteria break down meat proteins and fats causing food to deteriorate and develop unpleasant odors, tastes, and textures. Fruits and vegetables get mushy or slimy and meat develops a bad odor. Most people would not eat spoiled food. However, if they did, they probably would not get seriously sick. Bacteria such as Pseudomonas spp. or Brochotrix thermosphacta cause slime, discoloration and odors, but don’t produce toxins. There are different spoilage bacteria and each reproduces at specific temperatures. Some can grow at the low temperatures in the refrigerator or freezer.
It is commonly believed that the presence of bacteria creates an immense danger, but this belief is far from the truth. The fact is that a very small percentage of bacteria can place us in any danger, and most of us with a healthy immune system are able to fight them off. Pathogenic bacteria cause illness. They grow rapidly in the “Danger Zone” - the temperatures between 40 and 140° F - and do not generally affect the taste, smell, or appearance of food. Food that is left too long at warm temperatures could be dangerous to eat, but smell and look just fine. Clostridium botulinum, Bacillus cereus or Staphylococcus aureus infect food with toxin which will bring harm to us in just a few hours. Still others, like Salmonella or Escherichia coli will find their way with infected meat into our intestines, and if present in sufficient numbers, will pose a serious danger. Pathogenic bacteria hate cold conditions and lie dormant at low temperatures waiting for an opportunity to jump into action when the conditions get warmer again. They all die when submitted to the cooking temperature of 160º F (72º C), but some sausages are never cooked and different strategies must be implemented to keep them at bay. Fighting bacteria is a never ending battle, but at least we can do our best to turn the odds in our favor.
Without beneficial bacteria it will not be possible to make fermented sausages, yogurt, saurkraut, cheese or wine.. They are naturally occurring in foods and meat meat, but in most cases they are added into the meat in the form of starter cultures. There are two classes of beneficial (friendly) bacteria:
- Lactic acid producing bacteria - Lactobacillus, Pediococcus.
- Color and flavor forming bacteria - Staphylococcus, Kocuria (previously known as Micrococcus).
Although lactic acid producing bacteria are used mainly to produce fermented products, color and flavor forming bacteria are needed to brake Nitrate into nitrite and are often added to develop a stronger red color of meats.
Destruction of Bacteria
Most pathogenic bacteria, including Salmonella, Escherichia coli 0157:H7, Listeria monocytogenes, and Campylobacter, can be fairly easily destroyed using a mild cooking process. Maintaining a minimum temperature within the range of 130-165º F (54 -74º C) for a specific amount of time will kill them. However, cooking at low temperatures will not destroy these toxins once they have formed in food.
Spoilage bacteria (Pseudomonas spp.) need oxygen to survive and applying a vacuum (removing air) during mixing and stuffing is an effective way to inhibit their growth. At home, a precaution must be made so that the sausage mix is stuffed firmly and any air pockets which are visible in a stuffed casing are pricked with a needle. Oxygen also affects the development of proper curing color and promotes rancidity in fats.
Major pathogenic (dangerous) bacteria that cause food based infection or intoxication
Salmonella is a rod shaped, motile bacterium, Gram-negative nonsporeforming commonly occurring in animals, especially in poultry and swine. It is regularly found in water, soil, insects, factory surfaces, kitchen surfaces, animal feces, raw meats, raw poultry and raw seafoods. Salmonella typhi and the paratyphoid bacteria are normally caused septicemic (the invasion and persistence of pathogenic bacteria in the blood-stream ) and produce typhoid or typhoid-like fever in humans. Other forms of salmonellosis generally produce milder symptoms.
- Infective dose
as few as 15-20 cells; depends upon age and health of host, and strain differences among the members of the genus.
Raw meats, poultry, eggs, milk and dairy products, fish, shrimp, frog legs, yeast, coconut, sauces and salad dressing, cake mixes, cream-filled desserts and toppings, dried gelatin, peanut butter, cocoa, and chocolate. Various Salmonella species have long been isolated from the outside of egg shells. The present situation with S. enteritidis is complicated by the presence of the organism inside the egg, in the yolk. This and other information strongly suggest vertical transmission, i.e., deposition of the organism in the yolk by an infected layer hen prior to shell deposition. Foods other than eggs have also caused outbreaks of S. enteritidis disease.
It is estimated that from 2 to 4 million cases of salmonellosis occur in the U.S. annually. The incidence of salmonellosis appears to be rising both in the U.S. and in other industrialized nations. S. enteritidis isolations from humans have shown a dramatic rise in the past decade, particularly in the northeast United States (6-fold or more), and the increase in human infections is spreading south and west, with sporadic outbreaks in other regions.
S. typhi and S. paratyphi A, B, and C produce typhoid and typhoid-like fever in humans. Various organs may be infected, leading to lesions. The fatality rate of typhoid fever is 10% compared to less than 1% for most forms of salmonellosis. S. dublin has a 15% mortality rate when septicemic in the elderly, and S. enteritidis is demonstrating approximately a 3.6% mortality rate in hospital/nursing home outbreaks, with the elderly being particularly affected.
Salmonella septicemia (the invasion and persistence of pathogenic bacteria in the blood-stream ) has been associated with subsequent infection of virtually every organ system.
Gram-negative bacteria have thinner cell walls and appear red under microscope after treatment with a coloring dye. Gram-positive bacteria have thicker cell walls and appear violet under microscope after treatment with a coloring dye.
Clostridium botulinum is an anaerobic (an organism living in the absence of air or free oxygen), Gram-positive (a cell with a thick wall), spore-forming rod that produces a potent neurotoxin. (toxin that acts on the nervous system). The spores (a dormant nonreproductive body formed by certain bacteria in response to adverse environmental conditions) are heat-resistant and can survive in foods that are incorrectly or minimally processed. Seven types (A, B, C, D, E, F and G) of botulism are recognized, based on the antigenic specificity of the toxin produced by each strain. Types A, B, E and F cause human botulism. Types C and D cause most cases of botulism in animals. Animals most commonly affected are wild fowl and poultry, cattle, horses and some species of fish. Foodborne botulism (as distinct from wound botulism and infant botulism) is a severe type of food poisoning caused by the ingestion of foods containing the potent neurotoxin formed during growth of the organism. The toxin is heat labile and can be destroyed if heated at 80°C for 10 minutes or longer.
The organism and its spores are widely distributed in nature. They occur in both cultivated and forest soils, bottom sediments of streams, lakes, and coastal waters, and in the intestinal tracts of fish and mammals, and in the gills and viscera of crabs and other shellfish. The types of foods involved in botulism vary according to food preservation and eating habits in different regions. Any food that is conducive to outgrowth and toxin production, that when processed allows spore survival, and is not subsequently heated before consumption can be associated with botulism. Almost any type of food that is not very acidic (pH above 4.6) can support growth and toxin production by C. botulinum. Botulinal toxin has been demonstrated in a considerable variety of foods, such as canned corn, peppers, green beans, soups, beets, asparagus, mushrooms, ripe olives, spinach, tuna fish, chicken and chicken livers and liver pate, and luncheon meats, ham, sausage, stuffed eggplant, lobster, and smoked and salted fish.
It is the ingestion of preformed toxin that causes botulism, not ingestion of the spores or vegetative organism. The toxin itself is rapidly destroyed by heat, such as in thorough cooking. However, the spores which produce the toxin are heat-tolerant and will survive boiling at 100º C (212º F)for an extended period of time.
The incidence of the disease is low, but the mortality rate is high if not treated immediately and properly. Most of the 10 to 30 outbreaks that are reported annually in the United States are associated with inadequately processed, home-canned foods, but occasionally commercially produced foods have been involved in outbreaks. Sausages, meat products, canned vegetables and seafood products have been the most frequent vehicles for human botulism.
Botulinum toxin causes flaccid paralysis by blocking motor nerve terminals at the myoneural junction. The flaccid paralysis progresses symmetrically downward, usually starting with the eyes and face, to the throat, chest and extremities. When the diaphragm and chest muscles become fully involved, respiration is inhibited and death from asphyxia results. Recommended treatment for foodborne botulism includes early administration of botulinal antitoxin (available from CDC) and intensive supportive care (including mechanical breathing assistance). All people are believed to be susceptible to the foodborne intoxication.
Much more information on botulism can be found here.
S. aureus is a spherical bacterium (coccus) which on microscopic examination appears in pairs, short chains, or bunched, grape-like clusters. These organisms are Gram-positive (a cell with a thick wall). Some strains are capable of producing a highly heat-stable protein toxin (a poisonous substance) that causes illness in humans.
- Infective dose
a toxin dose of less than 1.0 microgram in contaminated food will produce symptoms of staphylococcal intoxication. This toxin level is reached when S. aureus populations exceed 100,000 per gram.
Foods that are frequently incriminated in staphylococcal food poisoning include meat and meat products; poultry and egg products; salads such as egg, tuna, chicken, potato, and macaroni; bakery products such as cream-filled pastries, cream pies, and chocolate eclairs; sandwich fillings; and milk and dairy products. Foods that require considerable handling during preparation and that are kept at slightly elevated temperatures after preparation are frequently involved in staphylococcal food poisoning. Staphylococci exist in air, dust, sewage, water, milk, and food or on food equipment, environmental surfaces, humans, and animals. Humans and animals are the primary reservoirs. Staphylococci are present in the nasal passages and throats and on the hair and skin of 50 percent or more of healthy individuals. This incidence is even higher for those who associate with or who come in contact with sick individuals and hospital environments. Although food handlers are usually the main source of food contamination in food poisoning outbreaks, equipment and environmental surfaces can also be sources of contamination with S. aureus. Human intoxication is caused by ingesting enterotoxins produced in food by some strains of S. aureus, usually because the food has not been kept hot enough (60°C, 140°F, or above) or cold enough (7.2°C, 45°F, or below).
The true incidence of staphylococcal food poisoning is unknown for a number of reasons, including poor responses from victims during interviews with health officials; misdiagnosis of the illness, which may be symptomatically similar to other types of food poisoning (such as vomiting caused by Bacillus cereus toxin); inadequate collection of samples for laboratory analyses; and improper laboratory examination. Of the bacterial pathogens causing foodborne illnesses in the U.S. (127 outbreaks, 7,082 cases recorded in 1983), 14 outbreaks involving 1,257 cases were caused by S. aureus. These outbreaks were followed by 11 outbreaks (1,153 cases) in 1984, 14 outbreaks (421 cases) in 1985, 7 outbreaks (250 cases) in 1986 and one reported outbreak (100 cases) in 1987.
Death from staphylococcal food poisoning is very rare, although such cases have occurred among the elderly, infants, and severely debilitated persons. All people are believed to be susceptible to this type of bacterial intoxication; however, intensity of symptoms may vary.
The onset of symptoms in staphylococcal food poisoning is usually rapid and in many cases acute, depending on individual susceptibility to the toxin, the amount of contaminated food eaten, the amount of toxin in the food ingested, and the general health of the victim. The most common symptoms are nausea, vomiting, retching, abdominal cramping, and prostration. Some individuals may not always demonstrate all the symptoms associated with the illness. In more severe cases, headache, muscle cramping, and transient changes in blood pressure and pulse rate may occur. Recovery generally takes two days, However, it us not unusual for complete recovery to take three days and sometimes longer in severe cases.
Campylobacter jejuni is a Gram-negative (a cell with a thin wall) slender, curved, and motile rod. It is a microaerophilic organism, which means it has a requirement for reduced levels of oxygen. It is relatively fragile, and sensitive to environmental stresses (e.g., 21% oxygen, drying, heating, disinfectants, acidic conditions). Because of its microaerophilic characteristics the organism requires 3 to 5% oxygen and 2 to 10% carbon dioxide for optimal growth conditions. This bacterium is now recognized as an important enteric (intestinal) pathogen. Before 1972, when methods were developed for its isolation from feces, it was believed to be primarily an animal pathogen causing abortion and enteritis in sheep and cattle. Surveys have shown that C. jejuni is the leading cause of bacterial diarrheal illness in the United States. It causes more disease than Shigella spp. and Salmonella spp. combined.
- Infective dose
The infective dose of C. jejuni is considered to be small. Human feeding studies suggest that about 400-500 bacteria may cause illness in some individuals, while in others, greater numbers are required.
C. jejuni frequently contaminates raw chicken. Surveys show that 20 to 100% of retail chickens are contaminated. This is not overly surprising since many healthy chickens carry these bacteria in their intestinal tracts. Raw milk is also a source of infections. The bacteria are often carried by healthy cattle and by flies on farms. Non-chlorinated water may also be a source of infections. However, properly cooking chicken, pasteurizing milk, and chlorinating drinking water will kill the bacteria.
C.jejuni is easily destroyed by heat. Bacteria is sensitive to salt (>2%) and very sensitive to drying.
C. jejuni is the leading cause of bacterial diarrhea in the U.S. There are probably numbers of cases in excess of the estimated cases of salmonellosis (2- to 4,000,000/year). The estimated case/fatality ratio for all C. jejuni infections is 0.1, meaning one death per 1,000 cases. Fatalities are rare in healthy individuals and usually occur in cancer patients or in the otherwise debilitated.
Campylobacter jejuni causes food and waterborne gastroenteritis, and it must survive passage through the stomach in order to reach the gastrointestinal tract.C. jejuni infection causes diarrhea, which may be watery or sticky and can contain blood (usually occult) and fecal leukocytes (white cells). Other symptoms often present are fever, abdominal pain, nausea, headache and muscle pain. The illness usually occurs 2-5 days after ingestion of the contaminated food or water. Illness generally lasts 7-10 days, but relapses are not uncommon (about 25% of cases). Most infections are self-limiting and are not treated with antibiotics. However, treatment with erythromycin does reduce the length of time that infected individuals shed the bacteria in their feces.
Complications are relatively rare, but infections have been associated with reactive arthritis, hemolytic uremic syndrome, and following septicemia (the invasion and persistence of pathogenic bacteria in the blood-stream), infections of nearly any organ.
This is a Gram-positive bacterium ( a cell with a thick wall), motile by means of flagella. Some studies suggest that 1-10% of humans may be intestinal carriers of L. monocytogenes. It has been found in at least 37 mammalian species, both domestic and feral, as well as at least 17 species of birds and possibly some species of fish and shellfish. It can be isolated from soil, silage, and other environmental sources. L. monocytogenes is quite hardy and resists the deleterious effects of freezing, drying, and heat remarkably well for a bacterium that does not form spores. Most L. monocytogenes are pathogenic to some degree.
- Infective dose
The infective dose of L. monocytogenes is unknown but is believed to vary with the strain and susceptibility of the victim. From cases contracted through raw or supposedly pasteurized milk, it is safe to assume that in susceptible persons, fewer than 1,000 total organisms may cause disease. L. monocytogenes may invade the gastrointestinal epithelium. Once the bacterium enters the host's monocytes, macrophages, or polymorphonuclear leukocytes, it is bloodborne (septicemic) and can grow. Its presence intracellularly in phagocytic cells also permits access to the brain and probably transplacental migration to the fetus in pregnant women.
L. monocytogenes has been associated with such foods as raw milk, supposedly pasteurized fluid milk, cheeses (particularly soft-ripened varieties), ice cream, raw vegetables, fermented raw-meat sausages, raw and cooked poultry, raw meats (all types), and raw and smoked fish. Its ability to grow at temperatures as low as 3°C permits multiplication in refrigerated foods.
The 1987 incidence data prospectively collected by CDC suggests that there are at least 1600 cases of listeriosis with 415 deaths per year in the U.S. The vast majority of cases are sporadic, making epidemiological links to food very difficult.
The manifestations of listeriosis include septicemia, meningitis (or meningoencephalitis), encephalitis, and intrauterine or cervical infections in pregnant women, which may result in spontaneous abortion (2nd/3rd trimester) or stillbirth. The onset of the aforementioned disorders is usually preceded by influenza-like symptoms including persistent fever. It was reported that gastrointestinal symptoms such as nausea, vomiting, and diarrhea may precede more serious forms of listeriosis or may be the only symptoms expressed. Gastrointestinal symptoms were epidemiologically associated with use of antacids or cimetidine. The onset time to serious forms of listeriosis is unknown but may range from a few days to three weeks. The onset time to gastrointestinal symptoms is unknown but is probably greater than 12 hours.
Most healthy persons probably show no symptoms. The "complications" are the usual clinical expressions of the disease.
When listeric meningitis occurs, the overall mortality may be as high as 70%; from septicemia 50%, from perinatal/neonatal infections greater than 80%. In infections during pregnancy, the mother usually survives. Successful treatment with parenteral penicillin or ampicillin has been reported. Trimethoprim-sulfamethoxazole has been shown effective in patients allergic to penicillin.
Currently, there are four recognized classes of enterovirulent E. coli (collectively referred to as the EEC group) that cause gastroenteritis in humans. Among these is the enterohemorrhagic (EHEC) strain designated E. coli O157:H7. E. coli is a normal inhabitant of the intestines of all animals, including humans. When aerobic culture methods are used, E. coli is the dominant species found in feces. Normally E. coli serves a useful function in the body by suppressing the growth of harmful bacterial species and by synthesizing appreciable amounts of vitamins. A minority of E. coli strains are capable of causing human illness by several different mechanisms. E. coli serotype O157:H7 is a rare variety of E. coli that produces large quantities of one or more related, potent toxins that cause severe damage to the lining of the intestine. These toxins [verotoxin (VT), shiga-like toxin] are closely related or identical to the toxin produced by Shigella dysenteriae. The illness is characterized by severe cramping (abdominal pain) and diarrhea which is initially watery but becomes grossly bloody. Occasionally vomiting occurs. Fever is either low-grade or absent. The illness is usually self-limited and lasts for an average of 8 days. Some individuals exhibit watery diarrhea only.
- Infective dose
unknown, but from a compilation of outbreak data, including the organism's ability to be passed person-to-person in the day-care setting and nursing homes, the dose may be similar to that of Shigella spp. (as few as 10 organisms).
Undercooked or raw hamburger (ground beef) has been implicated in many of the documented outbreaks, however E. coli O157:H7 outbreaks have implicated alfalfa sprouts, unpasteurized fruit juices, dry-cured salami, lettuce, game meat, and cheese curds.
Hemorrhagic colitis infections are not too common, but this is probably not reflective of the true frequency. In the Pacific Northwest, E. coli O157:H7 is thought to be second only to Salmonella as a cause of bacterial diarrhea. Because of the unmistakable symptoms of profuse, visible blood in severe cases, those victims probably seek medical attention, but less severe cases are probably more numerous.
Some victims, particularly the very young, have developed the hemolytic uremic syndrome (HUS), characterized by renal failure and hemolytic anemia. From 0 to 15% of hemorrhagic colitis victims may develop HUS. The disease can lead to permanent loss of kidney function. In the elderly, HUS, plus two other symptoms, fever and neurologic symptoms, constitutes thrombotic thrombocytopenic purpura (TTP). This illness can have a mortality rate in the elderly as high as 50%. All people are believed to be susceptible to hemorrhagic colitis, but young children and the elderly appear to progress to more serious symptoms more frequently.
Shigella are Gram-negative (a cell with a thin wall), nonmotile, nonsporeforming rod-shaped bacteria. The illness caused by Shigella (shigellosis) accounts for less than 10% of the reported outbreaks of foodborne illness in this country. Shigella rarely occurs in animals; principally a disease of humans except other primates such as monkeys and chimpanzees. The organism is frequently found in water polluted with human feces.
Salads (potato, tuna, shrimp, macaroni, and chicken), raw vegetables, milk and dairy products, and poultry. Contamination of these foods is usually through the fecal-oral route. Fecally contaminated water and unsanitary handling by food handlers are the most common causes of contamination.
An estimated 300,000 cases of shigellosis occur annually in the U.S. The number attributable to food is unknown, but given the low infectious dose, it is probably substantial.
Abdominal pain; cramps; diarrhea; fever; vomiting; blood, pus, or mucus in stools; tenesmus. Infections are associated with mucosal ulceration, rectal bleeding, drastic dehydration; fatality may be as high as 10-15% with some strains. Reiter's disease, reactive arthritis, and hemolytic uremic syndrome are possible sequelae that have been reported in the aftermath of shigellosis. Infants, the elderly, and the infirm are susceptible to the severest symptoms of disease, but all humans are susceptible to some degree. Shigellosis is a very common malady suffered by individuals with acquired immune deficiency syndrome (AIDS) and AIDS-related complex, as well as non-AIDS homosexual men.
Bacillus cereus is a Gram-positive (a cell with a thick wall), facultatively aerobic (a bacterium that can live with or without air) sporeformer whose cells are large rods and whose spores (a dormant nonreproductive body formed by certain bacteria in response to adverse environmental conditions) do not swell the sporangium (organ containing or producing spores.
- Infective dose
The presence of large numbers of B. cereus (greater than 10^6 organisms/g) in a food is indicative of active growth and proliferation of the organism and is consistent with a potential hazard to health.
A wide variety of foods including meats, milk, vegetables, and fish have been associated with the diarrheal type food poisoning. The vomiting-type outbreaks have generally been associated with rice products; however, other starchy foods such as potato, pasta and cheese products have also been implicated. Food mixtures such as sauces, puddings, soups, casseroles, pastries, and salads have frequently been incriminated in food poisoning outbreaks.
In 1980, 9 outbreaks were reported to the Centers for Disease Control and included such foods as beef, turkey, and Mexican foods. In 1981, 8 outbreaks were reported which primarily involved rice and shellfish. Other outbreaks go unreported or are misdiagnosed because of symptomatic similarities to Staphylococcus aureus intoxication (B. cereus vomiting-type) or C. perfringens food poisoning (B. cereus diarrheal type).
The onset of watery diarrhea, abdominal cramps, and pain occurs 6-15 hours after consumption of contaminated food. Nausea may accompany diarrhea, but vomiting (emesis) rarely occurs. Symptoms persist for 24 hours in most instances. The emetic type of food poisoning is characterized by nausea and vomiting within 0.5 to 6 h after consumption of contaminated foods. Occasionally, abdominal cramps and/or diarrhea may also occur. Duration of symptoms is generally less than 24 h.
Although no specific complications have been associated with the diarrheal and vomiting toxins produced by B. cereus, other clinical manifestations of B. cereus invasion or contamination have been observed. They include bovine mastitis, severe systemic and pyogenic infections, gangrene, septic meningitis, cellulitis, panophthalmitis, lung abscesses, infant death, and endocarditis. All people are believed to be susceptible to B. cereus food poisoning.
Escherichia coli 0157:H7
The above was based on data from The United States Food and Drug Administration.
Yeasts and Molds
Yeast and molds grow much slower than bacteria and they develop later in the drying process. This means they are normally part of the traditionally made sausage process. Yeasts need little oxygen to survive, and live on the surface or near the surface inside of the sausage. Molds are aerobic (need oxygen) and will grow on the surface of the sausage only. On fermented European sausages, the development of mold is often seen as a desired feature as it contributes to the flavor of the sausage. Smoking sausages during or after fermentation, will prevent the growth of mold. If mold develops and is not desired, it can be easily wiped off with a cloth saturated in vinegar. Because molds can grow only on the outside of the sausage, there is nothing wrong with the meat itself.
Toxins of most concern are produced by Clostridium botulinum, Clostridium perfringens, Bacillus cereus, and Staphylococcus aureus. All are the result of the growth of bacteria in foods that have been mishandled. These bacteria are common in the environment and are often found on carcasses. Proper cooking, fermentation, cooling, and storage of food can prevent the growth of these bacteria and more importantly, the production of their toxins. Thermal processing (canning) at temperatures of greater than 240º F (115º C) for a specific amount of time is necessary to destroy most spores and toxins. Clostridium botulinum toxin is the most toxic substance known to man (it is estimated that 1 pound of toxin can kill all the people on earth).