Basic guide: Salmonella infections

Salmonellosis — an infection with bacteria called Salmonella — has been known to be a common cause of food poisoning for more than a hundred years.

Infants, elderly people, and those with weakened immune systems are more likely than others to develop severe illness.

Salmonella infections

What are the signs & symptoms of Salmonella infections?

Most people infected with Salmonella develop diarrhea, fever, and abdominal cramps 12 to 72 hours after infection. The illness usually lasts 4 to 7 days, and most people recover without treatment.

However, in some people, the diarrhea may be so severe that the patient needs to be hospitalized. When severe infection occurs, Salmonella can be fatal unless the person is treated promptly with antibiotics. (Typhoid fever, a more serious disease caused by Salmonella Typhi, is not common in the United States, but frequently occurs in developing countries.)

How do people get Salmonella?

Salmonella are usually transmitted to humans by eating foods contaminated with animal feces. Contaminated foods usually look and smell normal. Contaminated foods are often of animal origin, such as beef, poultry, milk, or eggs — but any food, including vegetables, may become contaminated, though thorough cooking kills Salmonella.

Symptoms of salmonella infections

  • Diarrhea (which may be bloody)
  • Vomiting
  • Fever
  • Abdominal cramps
Food may also become contaminated by the hands of an infected food handler — for example, one who did not wash hands properly with soap after using the bathroom.

Salmonella may also be found in the feces of some pets, especially those with diarrhea, and people can become infected if they do not wash their hands after contact with pets or pet feces.

Reptiles, such as turtles, lizards, and snakes, are particularly likely to harbor Salmonella in their intestinal tracts, and many chicks and young birds carry Salmonella in their feces. People should always wash their hands immediately after handling a reptile or bird, even if the animal is healthy. Adults should also assure that children wash their hands after handling a reptile or bird, or after touching its environment. (Also see Reptiles & amphibians as pets: Not so safe for young kids.)



How can Salmonella infections be diagnosed?

Many different kinds of illnesses can cause diarrhea, fever, or abdominal cramps. Determining that Salmonella is the cause of the illness depends on laboratory tests that identify Salmonella in the stool of an infected person. Once Salmonella has been identified, further testing can determine its specific type.

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How can Salmonella infections be treated?

Salmonella gastrointestinal infections usually resolve in 5-7 days and most do not require treatment other than oral fluids. People with severe diarrhea may require rehydration with intravenous fluids.

Antibiotic therapy can prolong the duration of excretion of non-typhoidal Salmonella, and is recommended only for patients with severe illness (e.g., those with severe diarrhea, high fever, bloodstream infection, or who need hospitalization) or those at risk of severe disease or complications, including young infants, older adults (over 65 years old) and immunocompromised people.

Antibiotic resistance is increasing among some Salmonellabacteria; therefore, susceptibility testing can help guide appropriate therapy. Choices for antibiotic therapy for severe infections include fluoroquinolones, third-generation cephalosporins, and ampicillin (for susceptible infections).

How common is Salmonellosis?

Every year, approximately 42,000 cases of salmonellosis are reported in the United States. Because many milder cases are not diagnosed or reported, the actual number of infections may be twenty-nine or more times greater. There are many different kinds of Salmonella bacteria. Salmonella serotype Typhimurium and Salmonella serotype Enteritidis are the most common in the United States. Salmonellosis is more common in the summer than winter.

Children are the most likely to get salmonellosis. The rate of diagnosed infections in children less than five years old is higher than the rate in all other people. Young children, the elderly, and the immunocompromised are the most likely to have severe infections. It is estimated that approximately 400 people die each year with acute salmonellosis.

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Are there long-term consequences to a Salmonella infection?

People with diarrhea usually recover completely, although it may be several months before their bowel habits are entirely normal. A small number of people with Salmonella develop pain in their joints, irritation of the eyes, and painful urination. This is called reactive arthritis. It can last for months or years, and can lead to chronic arthritis which is difficult to treat. (Antibiotic treatment does not make a difference in whether or not the person develops arthritis.)

If you think that you or your child has a Salmonella infection, contact your health care provider immediately.

Quick tips for preventing salmonella

  • Cook poultry, ground beef, and eggs thoroughly.
  • Keep food properly refrigerated before cooking.
  • Chill foods promptly after serving and when transporting from one place to another.
  • Avoid eating high-risk foods, including raw or lightly cooked eggs, undercooked ground beef or poultry, and unpasteurized (raw) milk.
  • Separate cooked foods from ready-to-eat foods. Do not use utensils on cooked foods that were previously used on raw foods, and do not place cooked foods on plates where raw foods once were unless it has been cleaned thoroughly.
  • Cook foods to a safe internal temperature. Use a meat thermometer to make sure foods are cooked to a safe temperature.
  • If you are served undercooked meat, poultry or eggs in a restaurant, don’t hesitate to send it back to the kitchen for further cooking.
  • Wash hands, kitchen work surfaces, and utensils with soap and water immediately after they have been in contact with raw meat or poultry.
  • Be particularly careful with foods prepared for infants, the elderly, and the immunocompromised.
  • Wash hands with soap after handling reptiles, amphibians, birds, or baby chicks, and after contact with pet feces.
  • Avoid direct or even indirect contact between reptiles (turtles, iguanas, other lizards, snakes) and infants or immunocompromised people.
  • Wash your hand after contact with animals, their food or treats, or their living environment.
  • Don’t work with raw poultry or meat, and an infant (e.g., feed, change diaper) at the same time.
  • Mother’s milk is the safest food for young infants. Breastfeeding prevents salmonellosis and many other health problems.
  • Also see: How you can prevent salmonella infection in the kitchen
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Why the name Salmonella? The bacteria was discovered in 1885 by scientist Theobald Smith, who working as a research lab assistant in the Veterinary Division of the US Department of Agriculture. The administrator of the USDA was veterinary pathologist Daniel Elmer Salmon, for whom the  rod-shaped, Gram-negative bacteria was named.



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