Most Common Foodborne Pathogens

Contributors: Barbara Gordon, RDN, LD
salmonella bacterium


According to the Centers for Disease Control and Prevention, approximately 48 million Americans get sick, 128,000 are hospitalized and 3,000 die each year from food poisoning.

Bacteria, viruses and parasites are the sources of many food poisoning cases, usually due to improper food handling. Some bacteria, in small amounts, are not harmful to most healthy adults because the human body is equipped to fight them off. The trouble begins when certain bacteria and other harmful pathogens multiply and spread, which can happen when food is mishandled. Foods that are contaminated may not look, taste or smell any different from foods that are safe to eat. Symptoms of food poisoning vary and develop as quickly as 30 minutes to as long as several days after eating food that's been infected.

As identified by the CDC, eight known pathogens (bacteria, viruses and parasites) account for the majority of foodborne illness, hospitalization and death in the United States.


Salmonella is the name of a group of bacteria that causes the infection salmonellosis. It is one of the most common bacterial causes of diarrhea and the most common cause of foodborne-related hospitalizations and deaths. Salmonella is more severe in pregnant women, older adults, younger children and those with a weakened immune system. Because Salmonella bacteria can live in the intestinal tract of humans and other animals, it can spread easily unless you use proper hygiene and appropriate cooking methods.

Sources: You can contract salmonellosis by consuming raw and undercooked eggs, undercooked poultry and meat, contaminated raw fruits and vegetables (such as sprouts and melons), as well as raw milk and other dairy products that are made with unpasteurized milk. It also can be transmitted through contact with infected animals or infected food handlers who have not washed their hands after using the bathroom.

Prevention: Cook foods such as eggs, poultry and ground beef, thoroughly, to their recommended internal temperatures. Wash raw fruit and vegetables before peeling, cutting or eating. Avoid unpasteurized dairy products and raw or undercooked meats, poultry and seafood. Wash hands often, especially after handling raw meat or poultry. Clean kitchen surfaces and avoid cross-contamination.

Clostridium perfringens

Clostridium perfringens, also known as C. perfringens, is very common in our environment. It can multiply very quickly under ideal conditions. Infants, young children and older adults are most at risk.

Sources: Illness usually occurs by eating foods contaminated with large numbers of this bacteria that produce enough toxin to cause sickness in the form of abdominal cramping and diarrhea. C. perfringens is sometimes referred to as the "buffet germ" because it grows fastest in large portions of food, such as casseroles, stews and gravies that have been sitting at room temperature in the danger zone. If food isn't originally cooked, reheated or kept at the appropriate temperature, live bacteria may be consumed and cause illness.

Prevention: Cook food thoroughly and keep it out of the danger zone, above a temperature of 140°F or below 40°F. Practice leftover safety by dividing roasts and stews into smaller quantities for faster cooling and refrigerate right away. Leftovers should be reheated to an internal temperature of 165°F or higher before serving. However, any foods left out at room temperature for more than two hours should be thrown out and after only one hour if it’s 90 degrees or warmer.


Campylobacter is a common cause of diarrhea. Most cases of campylobacteriosis, the infection caused by Campylobacter bacteria, are associated with eating raw or undercooked poultry and meat or from cross-contamination of other foods by these items. Freezing reduces the number of Campylobacter bacteria on raw meat but will not kill them completely, so proper heating of foods is important. Campylobacteriosis occurs more frequently in the summer and is most common in infants and young children.

Sources: Sources include consuming raw and undercooked poultry and other meats, unpasteurized dairy products and untreated water or contaminated produce.

Prevention: Cook all foods thoroughly to their appropriate internal temperatures, prevent cross-contamination by using separate cutting boards when handling raw and cooked foods, don't drink unpasteurized milk or untreated water and wash hands frequently. Wash raw fruits and vegetables before peeling, cutting and eating.

Staphylococcus aureus

Staphylococcus aureus (staph) is commonly found on the skin, throats and nostrils of healthy people and animals. Therefore, it usually doesn't cause illness unless it is transmitted to food products where it can multiply and produce harmful toxins. Staphylococcal symptoms include nausea, stomach cramps, vomiting or diarrhea. Staphylococcal bacteria can be destroyed by cooking but their toxins are heat resistant and cannot. Anyone can develop a staph infection but certain groups of people are at greater risk, including people with chronic conditions such as diabetes, cancer, vascular disease, eczema and lung disease.

Sources: The bacteria can be found in unpasteurized dairy products and salty foods such as ham and other sliced meats. Foods that are made or come in contact with hands and require no additional cooking are at highest risk, including:

  • Salads, such as ham, egg, tuna, chicken, potato and macaroni
  • Bakery products, such as cream-filled pastries, cream pies and chocolate éclairs
  • Sandwiches.

Prevention: Keep foods out of the temperature danger zone and keep kitchen areas clean. Wash hands with soap and water, do not prepare or serve food if you have a nose or eye infection or if you have wounds or skin infections on your hands or wrists. 

E. coli O157:H7

Escherichia coli, better known as E. coli, are a large group of bacteria. Although most strains of E. coli are harmless, some can make you very sick. One strain, E. Coli O157:H7 (STEC) is commonly associated with food poisoning outbreaks because its effects can be extremely severe.

Sources: These include eating raw or undercooked ground beef or drinking unpasteurized beverages or dairy products.

Prevention: Wash your hands, cook meat (especially ground meat) and poultry thoroughly to their appropriate internal temperatures; avoid unpasteurized dairy products, juices or ciders; keep cooking surfaces clean; and prevent cross-contamination. Also, don't swallow water when playing or swimming in lakes, ponds, streams or pools.

Listeria monocytogenes

Eating food contaminated with Listeria monocytogenes bacteria causes listeriosis — a serious infection that primarily affects individuals who are at a high risk for food poisoning: older adults, pregnant women, young children and people with weakened immune systems. Listeria can grow at refrigerator temperatures where most other bacteria cannot grow.

Causes: Listeria is found in refrigerated, ready-to-eat foods such as hot dogs, deli meats, unpasteurized milk, raw sprouts, dairy products and raw and undercooked meat, poultry and seafood.

Prevention: Cook all foods to proper internal temperatures and reheat precooked foods to 165°F; wash raw fruits and vegetables before peeling, cutting or eating; separate uncooked meats and poultry from foods that are already cooked or ready-to-eat; wash hands thoroughly; store foods safely by making sure the temperature in your refrigerator is at or below 40F; maintain a clean refrigerator and kitchen area; and wash reusable grocery totes regularly.


Norovirus is one of the leading causes of food poisoning and often results in symptoms similar to stomach flu such as stomach cramping, nausea, vomiting and diarrhea. Norovirus spreads easily by coming in contact with someone who is infected, especially in crowded areas. Foods, drinks and surfaces also can become contaminated with the norovirus. Anyone can get sick with norovirus, but the illness can be especially serious for young children and older adults. You can contract norovirus many times in your life.

Sources: Fresh produce, shellfish, ice, fruit and ready-to-eat foods, especially salads, sandwiches and cookies that have been prepared by someone who is infected are sources of norovirus.

Prevention: Do not cook, prepare or serve foods or beverages while you are sick. Frequently wash your hands with soap and water for at least 20 seconds. Keep foods and utensils clean by washing all fruits and vegetables, cutting boards, knives, kitchen surface areas, table linens, cloth napkins and reusable grocery bags.

Toxoplasma gondii

Toxoplasma is a parasite that causes toxoplasmosis — a disease that can result in serious health problems in individuals who are at high risk for food poisoning: pregnant women, infants, older adults and people with weakened immune systems. Symptoms can be similar to flu and include swollen lymph glands or muscle aches and pains that last for months. Other symptoms affect the eyes, causing vision to be reduced or blurred or cause pain, redness or tearing.

Sources: Sources include eating undercooked, contaminated meat or using utensils or cutting boards that have had contact with raw meat; coming into contact with feces from an infected cat when cleaning the litter box; or drinking contaminated water. Toxoplasma also can be spread to infants if a mother has become infected before or while pregnant.

Prevention: Cook food to safe temperatures — a food thermometer should be used to ensure food has reached a safe internal temperature. Also, freeze meat properly; wash fruits and vegetables before peeling, cutting and eating; avoid unpasteurized dairy products; maintain clean cutting boards; and always wash your hands with soap and water. In addition, wear gloves when cleaning a cat's litter box or touching soil in case it is contaminated with cat feces, especially if pregnant or are at a higher risk of getting sick.

One of the best things you can do to reduce your risk of food poisoning is to practice safe food handling at home. Consult a physician if you think you or someone else has been sickened by food poisoning.

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