Quick Facts...
- Salmonella, Campylobacter, E. coli and Listeria
bacteria in food cause food infection.
- Staphylococcus and Clostridium botulinum bacteria
produce a toxin (or poison) as a by-product of growth and multiplication
in food and cause food intoxication.
- Clostridium perfringens can multiply in foods to sufficient
numbers to cause food poisoning.
- By following simple steps (clean, separate, cook, and chill) you can
prevent most food-related illness. And, when in doubt, throw it out!.
Food-borne infection is caused by bacteria in food. If bacteria become numerous and the food is eaten, bacteria may continue to grow in intestines and cause illness. Salmonella, Campylobacter, hemorrhagic E. coli and Listeria all cause
infections.
Food intoxication results from consumption of toxins (or poisons) produced
in food by bacterial growth. Toxins, not bacteria, cause illness. Toxins
may not alter the appearance, odor or flavor of food. Common kinds of
bacteria that produce toxins includeStaphylococcus aureus and
Clostridium botulinum. (See fact sheet 9.305, Botulism,
for more information on its prevention.) In the case of Clostridium
perfringens, illness is caused by toxins released in the gut when
large numbers of vegetative cells are eaten.
Salmonellosis
Salmonellosis is a form of food infection that may result when foods
containing Salmonella bacteria are consumed. Once eaten, the
bacteria may continue to live and grow in the intestine, set up an infection
and cause illness. The possibility and severity of the illness depends
in large part on the size of the dose, the resistance of the host and
the specific strain of Salmonella causing the illness.
The bacteria are spread through indirect or direct contact with the intestinal
contents or excrement of animals, including humans. For example, they
may be spread to food by hands that are not washed after using the toilet.
They also may be spread to raw meat during processing so that it is contaminated
when brought into the kitchen. Because of this, it is important to make
sure hands and working surfaces are thoroughly washed after contact with
raw meat, fish and poultry and before working with foods that require
no further cooking.
Salmonella bacteria grow at temperatures between 41 and 113
degrees F. They are readily destroyed by cooking to 160 F and do not grow
at refrigerator or freezer temperatures. They do survive refrigeration
and freezing, however, and will begin to grow again once warmed to room
temperature.
Symptoms of salmonellosis include headache, diarrhea, abdominal pain, nausea, chills, fever and vomiting. These usually
occur within 12 to 36 hours after eating contaminated food and may last two to seven days. Arthritis symptoms may follow
three to four weeks after onset of acute symptoms. Infants, the elderly or people already ill have the least resistance to
disease effects.
Foods commonly involved include eggs or any egg-based food, salads (such
as tuna, chicken or potato), poultry, beef, pork, processed meats, meat
pies, fish, cream desserts and fillings, sandwich fillings, raw sprouts,
and milk products. These foods may be contaminated at any of the many
points where the food is handled or processed from the time of slaughter
or harvest until it is eaten.
Campylobacteriosis
Campylobacteriosis or Campylobacter enteritis is caused by consuming
food or water contaminated with the bacteria Campylobacter jejuni.
C. jejuni commonly is found in the intestinal tracts of healthy animals
(especially chickens) and in untreated surface water. Raw and inadequately
cooked foods of animal origin and non-chlorinated water are the most common
sources of human infection (e.g. raw milk, undercooked chicken, raw hamburger,
raw shellfish). The organism grows best in a reduced oxygen environment,
is easily killed by heat (120 F), is inhibited by acid, salt and drying,
and will not multiply at temperatures below 85 F.
Diarrhea, nausea, abdominal cramps, muscle pain, headache and fever are common symptoms. Onset usually occurs two to
five days after eating contaminated food. Duration is two to seven days, but can be weeks with such complications as
urinary tract infections and reactive arthritis. Meningitis, recurrent colitis, acute cholecystitis, and Guillain-Barre syndrome
are rare complications. Deaths, also rare, have been reported.
Preventive measures for Campylobacter infections include pasteurizing
milk; avoiding post-pasteurization contamination; cooking raw meat, poultry
and fish; and preventing cross-contamination between raw and cooked or
ready-to-eat foods.
Listeriosis
Prior to the 1980s, listeriosis, the disease caused by Listeria monocytogenes,
was primarily of veterinary concern, where it was associated with abortions
and encephalitis in sheep and cattle. As a result of its wide distribution
in the environment, its ability to survive for long periods under adverse
conditions, and its ability to grow at refrigeration temperatures, Listeria
has since become recognized as an important food-borne pathogen. L.
monocytogenes is frequently carried by humans and animals. The organism
can grow in the pH range of 4.1 to 9.6. It is salt tolerant and relatively
resistant to drying, but easily destroyed by heat. (It grows between 34
F and 113 F).
Listeriosis primarily affects newborn infants, pregnant women, the elderly
and those with compromised immune systems. In a healthy non-pregnant person,
listeriosis may occur as a mild illness with fever, headaches, nausea
and vomiting. Among pregnant women, intrauterine or cervical infections
may result in spontaneous abortion or still birth. Infants born alive
may develop meningitis. The mortality rate in diagnosed cases is 20 to
35 percent. The incubation period is a few days to several weeks. Recent
cases have involved raw milk, soft cheeses made with raw milk, and raw
or refrigerated ready-to-eat meat, poultry or fish products.
Preventive measures for listeriosis include maintaining good sanitation,
turning over refrigerated ready-to-eat foods quickly, pasteurizing milk,
avoiding post-pasteurization contamination, and cooking foods thoroughly.
Staphylococcal Intoxication
Staphylococcus bacteria are found on the skin and in the nose
and throat of most people; people with colds and sinus infections are
often carriers. Infected wounds, pimples, boils and acne are generally
rich sources. Staphylococcus also are widespread in untreated
water, raw milk and sewage.
When Staphylococcus bacteria get into warm food and multiply,
they produce a toxin or poison that causes illness. The toxin is not detectable
by taste or smell. While the bacteria itself can be killed by temperatures
of 120 F, its toxin is heat resistant; therefore, it is important to keep
the staph organism from growing. Keep food clean to prevent its contamination,
keep it either hot (above 140 F) or cold (below 40 F) during serving time,
and as quickly as possible refrigerate or freeze leftovers and foods to
be served later.
Symptoms include abdominal cramps, vomiting, severe diarrhea and exhaustion. These usually appear within one to eight
hours after eating staph-infected food and last one or two days. The illness seldom is fatal.
Foods commonly involved in staphylococcal intoxication include protein foods such as ham, processed meats, tuna, chicken, sandwich fillings, cream fillings, potato and meat salads, custards, milk products and creamed potatoes. Foods that are handled frequently during preparation are prime targets for staphylococci contamination.
Clostridium Perfringens Food-Borne Illness
Clostridium perfringens belong to the same genus as the botulinum organism. However, the disease produced by C.
perfringens is not as severe as botulism and few deaths have occurred. Spores are found in soil, nonpotable water,
unprocessed foods and the intestinal tract of animals and humans. Meat and poultry are frequently contaminated with these
spores from one or more sources during processing.
Spores of some strains are so heat resistant that they survive boiling for four or more hours. Furthermore, cooking drives off oxygen, kills competitive organisms and heat-shocks the spores, all of which promote germination.
Once the spores have germinated, a warm, moist, protein-rich environment with
little or no oxygen is necessary for growth. If such conditions exist
(i.e., holding meats at warm room temperature for several hours or cooling
large pots of gravy or meat too slowly in the refrigerator), sufficient
numbers of vegetative cells may be produced to cause illness. Foods commonly
involved in clostridium illness include cooked, cooled, or reheated meats,
poultry, stews, meat pies, casseroles, and gravies.
Symptoms occur within eight to 24 hours after contaminated food is eaten. They
include acute abdominal pain and diarrhea. Nausea, vomiting and fever
are less common. Recovery usually is within one to two days, but symptoms
may persist for one or two weeks.
E. coli Hemorrhagic Colitis
Escherichia coli belong to a family of microorganisms called
coliforms. Many strains of E. coli live peacefully in the gut,
helping keep the growth of more harmful microorganisms in check. However,
one strain, E. coli O157:H7, causes a distinctive and sometimes
deadly disease.
Symptoms begin with nonbloody diarrhea one to five days after eating contaminated food, and progress to bloody diarrhea,
severe abdominal pain and moderate dehydration. In young children, hemolytic uremic syndrome (HUS) is a serious
complication that can lead to renal failure and death. In adults, the complications sometimes lead to thrombocytopenic
purpura (TPP), characterized by cerebral nervous system deterioration, seizures and strokes.
Ground beef is the food most associated with E. coli O157:H7
outbreaks, but other foods also have been implicated. These include raw
milk, unpasteurized apple juice and cider, dry-cured salami, homemade
venison jerky, sprouts, lettuce, spinach, and untreated water. Infected
food handlers and diapered infants with the disease likely help spread
the bacteria.
Preventive strategies for E. coli infections include thorough washing and other measures to reduce the presence of the microorganism on raw food, thorough cooking of raw animal products, and avoiding recontamination of cooked meat with raw meat. To be safe, cook ground meats to 160 F.
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165°F
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Figure 1: Temperature of food for control
of bacteria.
Turkey and chicken
Leftovers, stuffing & casseroles
Hot dogs and lunch meats
Ground beef and pork
Pork, ham and game meat
Egg dishes
Beef, lamb and veal steaks and roasts
Fish (flakes with a fork)
Eggs (firm yolk and white)
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| 160°F |
| 145°F |
Preventing Food-Borne Illness
Food-borne illness can be prevented. The following food handling practices
have been identified by the Food Safety and Inspection Service of USDA
as essential in preventing bacterial food-borne illness.
Purchase and Storage
- Keep packages of raw meat and poultry separate from other foods, particularly
foods to be eaten without further cooking. Use plastic bags or other
packaging to prevent raw juices from dripping on other foods or refrigerator
surfaces.
- Buy products labeled "keep refrigerated" only if they are stored in
a refrigerated case. Refrigerate promptly.
- Buy dated products before the label sell-by, use-by or pull-by date
has expired.
- Use an appliance thermometer to make sure your refrigerator is 40
degrees F or below and your freezer is 0 F or below.
Preparation
- Wash hands (gloved or not) with soap and water for 20 seconds before
preparing foods and after handling raw meat or poultry, touching animals,
using the bathroom, changing diapers, smoking or blowing your nose.
- Thaw only in refrigerator, under cold water changed every 30 minutes,
or in the microwave (followed by immediate cooking).
- Scrub containers and utensils used in handling uncooked foods with
hot, soapy water before using with ready-to-serve foods. Use separate
cutting boards to help prevent contamination between raw and cooked
foods.
- Stuff raw products immediately before cooking, never the night before.
- Don't taste raw meat, poultry, eggs, fish or shellfish. Use pasteurized
milk and milk products.
- Do not eat raw eggs. This includes milk shakes with raw eggs, Caesar
salad, Hollandaise sauce, and other foods like homemade mayonnaise,
ice cream or eggnog made from recipes that call for uncooked eggs.
- Use a meat thermometer to judge safe internal temperatures for cooked
foods (see Table 1.) If your microwave has a temperature probe, use
it.
- When using slow cookers or smokers, start with fresh rather than frozen,
chunks rather than roasts or large cuts, and recipes that include a
liquid. Check internal temperature in three spots to be sure food is
thoroughly cooked.
- Avoid interrupted cooking. Never partially cook products, to refrigerate
and finish later. Also, don't put food in the oven with a timer set
to begin cooking later in the day.
- If microwave cooking instructions on the product label are not appropriate
for your microwave, increase microwave time to reach a safe internal
temperature. Rotate, stir and/or cover foods to promote even cooking.
- Before tasting, boil all home-canned vegetables and meats 10 minutes
plus one minute per 1,000 feet.
Serving
- Wash hands with soap and water before preparing, serving, or eating
food. Serve cooked products on clean plates with clean utensils and
clean hands.
- Keep hot foods hot (above 140 F) and cold foods cold (below 40 F).
- In environmental temperatures of 90 F or warmer, leave cooked food out no longer than one hour before reheating, refrigerating or freezing. At temperatures below 90 F, leave out no more than two hours.
Handling Leftovers
- Wash hands before handling leftovers and use clean utensils and surfaces.
- Remove stuffing before cooling or freezing.
- Refrigerate or freeze cooked leftovers in small, covered shallow containers
(2 inches deep or less) within two hours after cooking. Leave airspace
around containers to help ensure rapid, even cooling.
- Use cooked leftovers within 4 days. Don’t taste leftovers to
determine safety.
- If reheating leftovers, cover and reheat to appropriate temperature
before serving (a rolling boil for sauces, soups, gravies, "wet" foods;
165 F for all others).
- If in doubt, throw it out. So they cannot be eaten by people or animals,
discard outdated, unsafe or possibly unsafe leftovers in the garbage
disposal or in tightly-wrapped packages.
References
Jay, J.M. Modern Food Microbiology. Gaithersburg, MD: Aspen
Publishers, 2000.
U.S. Food and Drug Administration. Bad Bug Book. Foodborne Pathogenic
Microorganisms and Natural Toxins Handbook. Available at: www.cfsan.fda.gov/~mow/intro.html.
Accessed 5/10/2008.
U.S. Department of Agriculture Food Safety and Inspection Service. 2006.
Basics for Handling Food Safely. Available at: www.fsis.usda.gov/PDF/Basics_for_Safe_Food_Handling.pdf.
Accessed 5/18/08.
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