Colorado State University Cooperative Extension Tips (Bacterial Food-Borne Illness)

Bacterial Food-Borne Illness

Preventing Salmonella poisoning

Food contaminated with Salmonella bacteria is a frequent cause of food-borne illness. Salmonella bacteria thrive at temperatures between 40 degrees and 140 degrees. The bacteria can survive at refrigerator or freezer temperatures, and, although the bacteria does not continue to grow at these temperatures, it will grow again once warmed to room temperature. The bacteria are destroyed by cooking food to 165 degrees.

The bacteria are spread through indirect or direct contact with human or animal intestinal contents or excrement. For example, the bacteria may accidentally be spread to food at meat processing plants; to produce that has come into contact with animal feces or to food by a person preparing or handling the food who does not wash his or her hands after using the toilet.

Symptoms of food-borne salmonella poisoning include headache, diarrhea, abdominal pain, nausea, chills, fever and vomiting. These symptoms occur 12 to 36 hours after eating contaminated food and may last two days to a week. Arthritis symptoms may follow three to four weeks after the onset of acute symptoms. Food that is the common cause of these illnesses include eggs or egg-based food, salads, tuna, chicken or potato, poultry, pork, processed meat, meat pies, fish, cream desserts and fillings, sandwich fillings and milk products.

For more information about bacterial food-borne illnesses, visit, click on publications, then fact sheets, then food and nutrition.

Preventing food-borne campylobacteriosis poisoning

Campylobacteriosis, or campylobacter enteritis, is an illness caused by eating food or drinking water contaminated with the Campylobacter jejuni bacteria. Until recently, this bacteria was primarily only something that veterinarians looked for, but it is now thought to be responsible for two and half times more food poisoning outbreaks per year than Salmonella.

The bacteria is commonly found in the intestinal tracts of healthy animals, especially chickens, and in untreated surface water. Raw and in adequately cooked animal food, such as undercooked chicken, raw hamburger or raw shellfish, and non-chlorinated water are the most common sources of human infection.

The bacteria is easily killed by heating food past 120 degrees and is also reduced when food is dried or when salt or acid are added. Diarrhea, nausea, abdominal cramps, muscle pain, headache and fever are common symptoms which usually occur two to five days after eating contaminated food. The symptoms usually last two days to a week, but can last longer with complications such as urinary tract infections and reactive arthritis. Other rare complications include meningitis and Guillain-Barre syndrome.

For more information about bacterial food-borne illnesses, visit, click on publications, then fact sheets, then food and nutrition.

Preventing food-borne listeriosis

Listeriosis, the disease caused by Listeria monocytogenes bacteria, is frequently carried by humans and animals. It primarily affects infants, pregnant women, the elderly and people with compromised immune systems. In other populations, the illness is milder with fever, headaches, nausea and vomiting as symptoms. Among pregnant women, intrauterine or cervical infections may cause spontaneous abortion or stillbirths. Infants born alive may develop meningitis.

The incubation period for the pathogens is a few days to three weeks. The bacteria has caused illnesses in people who have eaten contaminated cole slaw, deli meats, hot dogs, unpasturized milk and cheeses made with unpasturized milk. Preventative measures include maintaining good sanitation when preparing food, consuming only pasteurized milk and cooking food thoroughly.

For more information about bacterial food-borne illnesses, visit, click on publications, then fact sheets, then food and nutrition.

Clostridium Perfringens food-borne illness

Clostridium Perfringens belong to the same genus as the organism that causes botulism. However, the disease produced by C. perfringens is not as severe as botulism. These spores are in soil, nonpotable water, unprocessed food and the intestinal track of animals and humans. Poultry and meat are frequently contaminated with these spores from one or more sources during processing.

Some strains of this bacteria are so resistant to heat they can survive boiling for four or more hours. In fact, cooking can promote germination. Once the spores germinate, a warm, moist, protein-rich environment with little or no oxygen is necessary for growth.

If such conditions exist, such as in meats held at warm room temperature for several hours or large pots of gravy or meat cooling too slowly in a refrigerator, enough cells may be produced to cause illness. Symptoms from the bacteria occur within eight to 24 hours after contaminated food is eaten and include acute abdominal pain and diarrhea. Nausea, vomiting and fever are less common symptoms. People affected by this illness usually recover within one to two days, but symptoms may persist for one to weeks.

General tips to prevent food-borne illness

Purchasing and storing food:

  • Keep packages of raw meat and poultry separate from other food, particularly food to be eaten without further cooking. Use plastic bags or other packaging to prevent raw juices from dripping on other food or refrigerator surfaces.
  • Buy products labeled "keep refrigerated" only if they are stored and displayed in a refrigerated case in the grocery store. Refrigerate these items promptly after purchasing them.
  • Buy dated products before the sell-by; use-by or pull-by date on the label has expired.


  • Wash hands – gloved or not – with soap and water for 20 seconds before preparing food and after handling raw meat or poultry, touching animals, using the bathroom, changing diapers, smoking or blowing your nose.
  • Thaw frozen foods only in the refrigerator, under cold water changed every 30 minutes or in the microwave.
  • Scrub containers and utensils that have been in contact with raw food with hot soapy water before using them with prepared food. Use separate cutting boards for raw food and prepared food.
  • Don’t eat raw meat, poultry, eggs, fish or shellfish. Use pasteurized milk and milk products.
  • Never partially cook products and then refrigerate and finish cooking them later. Don’t put food in the oven with a timer set to begin cooking it later in the day.
  • Cook meat and poultry to a safe internal temperature (160 degrees or higher for meat, 180 degrees or higher for poultry). Check the temperature with a thermometer.

For more information about bacterial food-borne illnesses, visit, click on publications, then fact sheets, then food and nutrition.

Preventing E. coli contamination in home-grown produce and during food preparation

Is E. coli a risk from food out of the garden?

Fresh fruits and vegetables once were thought to be relatively free of disease-producing pathogens, but recent outbreaks of food-borne illness linked to these foods are becoming more common. Food-borne illness outbreaks have been linked to E. coli and Salmonella on apples, lettuce, cantaloupe and sprouts; Listeria monocytogenes on cabbage; Shigella on parsley and lettuce; and Cyclospora on imported raspberries.

Changes in microorganisms that cause illness have likely contributed to the increase in pathogens. Listeria monocytogenes, Clostridium botulinum and Bacillus cereus are naturally present in soil and their presence on produce is not uncommon. Salmonella, E. coli 0157:H7, Campylobacter jejuni, Vibrio cholerae, parasites and viruses can contaminate produce through raw or improperly treated compost manure, irrigation water containing untreated sewage or manure, and contaminated wash water. These foods may also be contaminated through contact with mammals, reptiles, birds, insects, unpasteurized animal products, and contaminated surfaces such as counter tops or the ground, and dirty human hands.

Wash produce in plain water or with water with bleach (1 to 3 teaspoons of chlorine bleach per gallon) followed by a plain-water rinse can reduce the number of pathogens and other microorganisms on produce. However, neither method is reliable to totally eliminate pathogens. Carefully controlling points of contamination before food is eaten is essential.

For more information, visit, click on publication, then fact sheets, then food and nutrition and view fact sheet No. 9.369.

Keep animals out of gardens to prevent E. coli contamination

Fresh produce and meat can be the source of many pathogens that cause food-borne illness. However, E. coli 0157:H7 is of particular concern because it is hardy and can cause illnesses with only a few cells. It can survive for extended periods of time in water and soil, in the temperatures of refrigerators and freezers and in dry conditions. People who become ill from E. coli often do so quickly and the consequences in susceptible people, particularly young children and the elderly, can be severe.

To minimize potential contamination of food grown in a garden, locate the garden away from any potential source of fresh manure, such as animal pens or compost piles. Keep pets, livestock and wildlife out of the garden, especially during the growing season. Check for manure contamination in runoff water from uphill neighbors.

For more information, visit, click on publication, then fact sheets, then food and nutrition and view fact sheet No. 9.369.

Check water sources for gardens for E. coli contamination

When using surface water in your garden, check the area around the water source. Is manure stored near the water? Is there a septic system near the water? Is manure applied to land near the water? Do livestock or wildlife have unrestricted access to the water? Are neighbors allowing contaminated runoff to enter the water?

It is important to prevent direct contact of potentially contaminated water with fruits, vegetables and other produce growing in the garden that will be eaten. Depending on the type of plant, different watering systems are more efficient for preventing contamination. If the edible portion of the crop is located above the soil, it is better to water with a drip system or a furrow or flood system than with sprinklers. This will limit direct contact between the water and the crop. When watering with a limited drinking water supply, save the "best" water for the period just before harvest. Avoid using potentially contaminated water within 30 days of harvest.

For more information, visit, click on publication, then fact sheets, then food and nutrition and view fact sheet No. 9.369.

Using manure to fertilize gardens while reducing chances of E. coli contamination

Manure is an excellent fertilizer and soil conditioner. However, don’t apply fresh manure to the soil in fruit or vegetable gardens. Even aged manure can contain E. coli. Composting manure properly will kill most E. coli. Composting manure at home is riskier than purchasing commercial compost because it is difficult to get the compost to reach proper temperatures for an adequate length of time throughout the entire compost pile.

In order for the manure pile to be composted properly, the following requirements must be met:

  • Mix the compost regularly. This is important not only for aeration but also to ensure that the entire pile has reached the required temperature.
  • Monitor the temperature. Long-handled thermometers are available for this purpose. The temperature must reach 130 to 140 degrees for at least two five-day heating cycles. Mix the compost between cycles.
  • After composting, allow the compost to cure for two to four months before applying it to your garden soil. This allows the beneficial bacteria to kill disease bacteria.

Only apply non-composted manure to gardens in the fall after harvest and mix it into the soil; do not leave it on the surface where it can have direct contact with the crop. Wait 120 days between application and crop harvest. E. coli bacteria can survive freezing temperatures, so this time requirement does not include periods when the soil is frozen.

For more information, visit, click on publication, then fact sheets, then food and nutrition and view fact sheet No. 9.369.

Preventing E. coli contamination in the kitchen

Food handling and preparation practices are the last line of defense for preventing infection from E. coli 0157:H7 and other food-borne pathogens. To prevent food contamination with these pathogens:

  • Wash hands thoroughly before working with food and after using the toilet, changing diapers, handling animals or helping people who have diarrhea.
  • Thoroughly wash raw fruits and vegetables before eating them to remove dirt, bacteria, residual pesticides and stubborn garden pests. Separate and individually rinse lettuce and spinach leaves.
  • Clean and sanitize cutting boards, utensils and surfaces used to prepare raw food before using them to prepare another product. Use 1 teaspoon of chlorine bleach per gallon of water.
  • Store fresh meat below produce in the refrigerator. Never place cooked meat on an unwashed plate that held raw meat.
  • Cook ground meats thoroughly to 160 degrees. Check the internal temperature with a thermometer.
  • Don’t drink raw milk and avoid unpasteurized juices or ciders.
  • Use only safe, treated water.
  • Refrigerate leftovers promptly.


What is botulism?

Food-borne botulism is the most common cause of reported cases of botulism, which average about 30 reports per year. Inactive botulism spores are found in food and water around the world and are relatively harmless; when spores germinate into actively growing cells, which produce a deadly toxin, they pose a health threat.

There are seven different types of the bacteria that cause botulism, called Clostridium botulinum. Three types of the bacteria are very resistant to heat, so they aren’t necessarily killed when food is cooked or processed with heat. However, these types of the bacteria eventually cause the food to smell spoiled – a good warning that the food containing the bacteria is not safe to eat. Three other types of the bacteria can grow at refrigerated temperatures. They are easily destroyed by heat but cause problems in food that is unheated or pasteurized; they do not cause an odor, making them difficult to detect.

Since the early 1900s, most of the problems with botulism in the United States have been caused by improperly home-canned foods. Colorado has one of the highest incidences of botulism in the United States because the soil in the western United States contains higher counts of botulism spores that are harmful to humans and the state’s high altitude. High altitude is a factor because the temperature of boiling water decreases as the altitude increases, which means that foods being canned or prepared may not reach temperatures high enough to destroy harmful botulism-causing toxins.

For more information about botulism, visit, click on publications, then fact sheets, then food and nutrition.

What are the symptoms of botulism?

Food-borne illness from botulism rarely occurs in the United States. However, it is a very serious illness, and Colorado has one of the highest incidences of botulism in the nation. Nation-wide, about 30 cases are reported each year.

Botulism can be caused by eating food contaminated with bacteria. Symptoms of food-borne botulism usually appear within 12 to 72 hours after the contaminated food is eaten, but the time can vary from six hour to eight days. The most significant symptoms are blurred double vision and difficulty in swallowing and speaking. Fever is absent early in the disease. Some symptoms, such as nausea, vomiting, abdominal pain, constipation, cramps, headache and fullness may lead to a false diagnosis of appendicitis, bowl obstruction or heart attack.

Unless food-borne botulism is treated promptly at the onset of symptoms, it can be fatal. Detection methods are relatively sophisticated and antitoxins are readily available.

For more information about botulism, visit, click on publications, then fact sheets, then food and nutrition.

How can botulism be prevented?

Botulism can be controlled if consumers take preventative steps when preparing food.

  • Wash food before cooking or processing it to reduce bacteria on the food.
  • Use only up-to-date home canning methods that are properly adjusted for altitude.
  • Before eating home-canned food, examine the container and product. A bulging lid or leaking jar are signs of spoilage, as are spurting liquid when the jar is opened, an off-odor or mold.
  • Dispose of spoiled food in a place where it will not be eaten by children and pets.

For more information about botulism, visit, click on publications, then fact sheets, then food and nutrition.