When present in food, several different microorganisms classified as bacteria are capable of causing illness among people. Among the comparatively common bacteria capable of causing illness when they are eaten are strains of Salmonellae, Streptococci, Clostridia, and Staphylococci. Illnesses resulting from eating food contaminated with Salmonella species or C. perfringens are classified as food infections. Salmonella and other food-borne bacterial poisonings are identified in Table 3.1.
Illnesses caused by eating foods containing the toxins produced by Staphylococcus aureus and C. botulinum are classified as food intoxication. To persons afflicted with the very unpleasant symptoms triggered either directly by the bacteria or by the toxin produced by some, this distinction is of little concern. The main focus of the victim in the throes of an episode is more likely to be the temporary conflict between wishing to live or wishing to die.
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1986 and subsequent years to prevent continuing spread of the disease to animals throughout the world. The infection originally spread through sale of animal feed containing animal tissue from infected sheep whose BSE did not produce immediate symptoms. International efforts are being made to prevent the spread of the disease by regulating the sources of cattle feed. The United States has been able to mostly avoid contamination by BSE due to a ban on feeding scrapie-infected tissue as far back as 1932 and the important ruminant feed ban that has been in effect since 1997. Additionally the United States has been proactive in putting up necessary firewalls to protect the U.S. food supply and its exports.
Figure 3.2
Chemist Chris Silva (left) and research leader J. Mark Carter load samples to characterize BSE prions with unprecedented precision using nanospray liquid chromatography coupled to mass spectroscopy. Courtesy of Agricultural Research Service.
http://www.cdc.gov/ ncidod/dvrd/prions/
—Information on prion diseases, including BSE.
http://www.fda.gov/Anim alVeterinary/Resourcesfor You/AnimalHealthLiteracy/ ucm136222.htm
—FDA site for BSE information.
http://www.cdc.gov/ foodsafety/diseases/
—Centers for Disease Control site information about food-borne illnesses.
http://www.cdc.gov/ foodsafety
—Food-borne illnesses and food safety information.
Table 3.1
Some Food-borne IllneSSeS From bacTerIa
Name of Illness What Causes It Symptoms Characteristics of Illness Control Measures
Salmonellosis Salmonellae. Bacteria widespread in
nature that live and grow in intestinal tracts of human beings and animals. About 1,200 species are known; one species causes typhoid fever. Bacteria grow and multiply at temperatures between 44° and 115°F (6–46°C).
Severe headache, followed by vomiting, diarrhea, abdominal cramps, and fever. Infants, elderly, and persons with low resistance are most susceptible. Severe infections cause high fever and may even cause death.
Transmitted by eating contaminated food or by contact with infected persons or carriers of the infection. Also transmitted by insects, rodents, and pets.
Onset: usually within 12–36 hours. Duration: usually 2–7 days.
Salmonellae in food are destroyed
by heating the food to a temperature of 140°F (60°C) and holding for 10 minutes or to higher temperatures for less time. Refrigeration at 45°F (7°C) inhibits the increase of Salmonellae, but they remain alive in the refrigerator or freezer and even in dried foods. Perfringens
poisoning
Clostridium perfringens.
Spore-forming bacteria that grow in the absence of oxygen. Spores can withstand temperatures
usually reached in cooking most foods. Surviving bacteria continue to grow in meats, gravies, and meat dishes held without proper refrigeration.
Nausea without vomiting, diarrhea, acute inflammation of stomach and intestines.
Transmitted by eating food contaminated with abnormally large numbers of bacteria.
Onset: usually within 8–20 hours. Duration: may persist for 24 hours.
To control growth of surviving bacteria on cooked meats that are to be eaten later, cool meats rapidly and refrigerate promptly at 40°F (5°C) or below.
Staphylococcal poisoning (frequently called staph)
Staphylococcus aureus. Bacteria
fairly resistant to heat. Bacteria growing in food produce a toxin that is extremely resistant to heat. Bacteria grow profusely with production of toxin at temperature between 44° and 115°F
(6–46°C).
Vomiting, diarrhea, prostration, abdominal cramps. Generally mild and often attributed to other causes.
Transmitted by food handlers who carry the bacteria and by eating the food containing the toxin.
Onset: usually within 3–8 hours. Duration: 1–2 days.
Growth of bacteria that produce toxin is inhibited by keeping hot foods above 140°F (60°C). Toxin is destroyed by boiling for several hours or heating the food in pressure cooker at 240°F (116°C) for 30 minutes.
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Name of Illness What Causes It Symptoms Characteristics of Illness Control Measures
Botulism Clostridium botulinum. Spore-
forming organisms that grow and produce toxin in the absence of oxygen, such as in a sealed container. The bacteria can produce a toxin in low-acid foods that have been held in the refrigerator for two weeks or longer. Spores are extremely heat resistant. Spores are harmless, but the toxin is a deadly poison.
Double vision, inability to swallow, speech difficulty, progressive respiratory paralysis. Fatality rate is high, in the United States about 65 percent.
Transmitted by eating food containing the toxin.
Onset: usually within 12–36 hours. Duration: 3–6 days.
Bacterial spores in food are destroyed by high temperatures obtained only in a pressure canner. More than 6 hours is needed to kill the spores at boiling temperatures (212°F or 100°C).
The toxin is destroyed by boiling for 10–20 minutes; time required depends on kind of food. Listeriosis Listeria monocytogenes. Bacteria
widespread in nature, particularly in animals. Multiplies slowly in cold to below freezing.
Fever, nausea, vomiting, diarrhea, fatigue; severe cases include meningitis, septicemia, endocarditis.
Transmitted by eating under- heated animal foods containing
L. monocytogenes. Onset: 12 hours. Duration: 5–10 days.
Avoid unpasteurized milk and soft cheese made from unpasteurized milk. Heat meats and fish to at least 160°F (71°C).
Campylobacter
infection
Campylobacter. Found commonly in
intestinal tract of pigs, poultry, and cattle. Easily killed by heat.
Fever, headache, muscle pain, diarrhea, nausea, stomach pain.
Transmitted by drinking untreated water or raw milk or by eating undercooked poultry or meat.
Don’t drink untreated water or unpasteurized milk. Avoid cross contamination after handling raw poultry and meat. Heat poultry and meat to at least 160°F (71°C). Traveler’s
diarrhea
May be caused by a wide variety of microorganisms, including bacteria such as enterotoxigenic E. coli and enteropathogenic E. coli, amoebae, and viruses.
Vomiting, diarrhea. Transmitted by eating contaminated raw or undercooked foods.
Onset: 8–44 hours. Duration: 24–30 hours.
Tight sanitation control. Adequate refrigeration of meat and poultry. Pasteurization of juices. Heat ground meats to at least 160°F (71°C) and other meats to at least 145°F (63°C). Heat poultry to at least 170°F (77°C).
Yersiniosis Yersinia enterocolitica Diarrhea, joint pain. Transmitted by eating undercooked pork or raw milk.
Onset: 4–7 days.
Duration: 3 weeks or longer.
Cook pork to 170°F (77°C); pasteurize milk.
Table 3.1 (continued)
food safety | chapter three
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salmonellosis Salmonella is a type of bacterium (Figure 3.3) capable of causing the gastrointestinal illness called salmonellosis. (The nomenclature recognizes the research of D. E. Salmon in 1885.) The symptoms of salmonellosis develop between 6 and 72 hours after eating the infected food, with 12 hours being the customary incubation period prior to evidence of symptoms. Evidence of salmonella infection includes abdominal cramps, fever, nausea, and diarrhea. Susceptibility to developing salmonellosis varies from one individual to another, but infants and people who already are sick are likely candidates. However, even healthy adults can develop salmonellosis if they eat a food with a high count of viable Salmonella. The increasing numbers of cases of salmonellosis being diagnosed may be the result of more problems with food sanitation, or it may simply mean that diagnosis is being done with increased accuracy, resulting in identification of the cause of the problem rather than the vague description of “something he ate.” Salmonellae are found commonly in protein foods such as pork, poultry, and eggs. To prevent serious episodes of intoxication by Salmonellae, keep foods containing these items at refrigerator temperatures or above the danger zone (above 140°F (60°C)) and minimize storage in the danger zone (40° to 140°F (5° to 60°C)). Frozen storage does not kill all Salmonellae in a food; even a storage period of six months at 0°F (–18°C) still is not sufficient to kill all Salmonellae. To ensure safety from Salmonellae infection, heat foods that might contain these bacteria to at least 140°F (60°C) and hold for 10 minutes, or use a somewhat higher tempera- ture for a shorter period.
Yersiniosis Yersinia enterocolitica in raw milk or pork can cause yersiniosis, a bacterial illness that may last three weeks or longer. These bacteria are related to Yersinia pestis, which caused the historically important bubonic plague. This problem can be avoided by pasteurizing milk and cooking pork adequately.
Perfringens Poisoning Perfringens poisoning is the result of the presence of an anaerobic bacterium, Clostridium perfringens. This bacteria is found in meats and meat dishes, and it can form spores that are extremely resistant to heat. The obvious means of protecting against
salmonella Type of bacteria capable of causing severe gastrointestinal upset when ingested in large quantities in a food.
salmonellosis Food-borne illness characterized by fever, nausea,
abdominal cramps, and diarrhea caused by eating food contaminated with viable Salmonella.
Yersinia enterocolitica
Bacteria sometimes found in raw and undercooked pork and raw milk, which cause yersiniosis.
Perfringens poisoning Food-borne illness caused by eating food containing viable C. perfringens.
clostridium perfringens Anaerobic, spore-forming bacteria that multiply readily at room temperature; ingestion can result in perfringens poisoning.
Figure 3.3
Salmonella enteritidis, a strain of Salmonella that can cause salmonellosis. Courtesy of Agricultural Research Service.
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section one | foundation for food studythis type of food contamination is to avoid infecting the meat and to prevent rapid reproduc- tion and increase in population. By avoiding storage at room temperature, this hazard can be reduced. Meats and meat-containing dishes should be served soon after they are prepared, or held for service at 140°F (60°C), and leftovers should be refrigerated promptly, not being allowed to sit on the kitchen counter for hours while cooling. Careful temperature control minimizes the reproductive capacity of these bacteria and is very important because of the strong resistance to heat exhibited by the spores when they have formed. The usual practice of simply heating foods to a temperature of 165°F (74°C) or more is not effective in killing C. perfringens. Avoidance of growth is the key to reducing the possibility of contracting perfringens poisoning. Nausea is a key symptom of perfringens poisoning. Vomiting does not occur, but there is a general feeling of discomfort due to irritation of both the stomach and the intestines.
staphylococcal infection Staphylococcal toxin infections (also referred to as staph) from food are common. This is due primarily to the ease with which infected food handlers transmit staphylococci. The signs prominently displayed in restrooms cautioning people to be sure to wash their hands well with soap are a public effort to help eliminate staph infections. The infec- tion is evidenced by vomiting, diarrhea, and stomach cramps and is due to eating food contain- ing the toxin produced by Staphylococcus aureus. This strain of bacteria reproduces with vigor in the danger zone between 44°F (6°C) and 115°F (46°C), resulting in a dangerous level of toxin in a matter of hours. Symptoms are evident within three to eight hours after ingestion and last for a day or two (although to the victim, it seems more like an eternity). toxin Poisonous substance produced by metabolic reactions;
S. aureus and C. botulinum
are the bacteria most commonly responsible for food poisoning from toxins.