Salmonella infection
Salmonella infection, also known as salmonellosis, is a bacterial infection caused by various types of Salmonella bacteria, leading to a spectrum of illnesses that primarily affect the gastrointestinal system and can also enter the bloodstream. It is commonly transmitted through the ingestion of contaminated food or contact with infected animals, such as farm animals and pet reptiles. Symptoms typically include fever, headache, muscle aches, abdominal pain, diarrhea, and vomiting, and the illness can last from six hours to three days.
The severity of the infection can vary based on the type of Salmonella, the amount ingested, and the individual's age and immune status. Young children and individuals with compromised immune systems are at greater risk for severe complications. Salmonella can cause conditions such as gastroenteritis, which is prevalent in the United States, and typhoid fever, which is less common and often acquired while traveling abroad. Diagnosis is made through culturing samples, and treatment generally focuses on managing fluid and electrolyte imbalances rather than antibiotics, unless severe symptoms arise. Preventative measures include proper hygiene, food safety practices, and vaccination in specific cases, particularly for typhoid fever.
Salmonella infection
ALSO KNOWN AS: Salmonellosis
ANATOMY OR SYSTEM AFFECTED: Blood, gastrointestinal system
DEFINITION: A broad spectrum of clinical diseases caused by many types of salmonella bacteria
CAUSES: Bacterial infection transmitted through ingestion or exposure to infected animals
SYMPTOMS: Fever, headache, muscle aches, abdominal pain, lethargy, diarrhea, vomiting
DURATION: Six hours to three days
TREATMENTS: Correction of fluid and salt abnormalities, supportive care
Causes and Symptoms
Salmonella are a group of bacteria that can cause infections, blood infections, and various local infections. All types of can be carried in the without symptoms after recovery from infection.
The clinical disease caused by salmonella depends on the type of bacteria, the amount of organisms ingested, and the age and immune status of the person infected. Infection with salmonella can take place with the ingestion of one or 100 million organisms. Increasing the dosage of decreases the and increases the severity of the resulting disease. After ingestion, the bacteria adhere to and invade the gastrointestinal tract. In the wall of the intestinal tract, salmonella survive and multiply in immune cells and then enter the bloodstream, where they proceed to any area of the body. Young infants and people with immune deficiencies and hemolytic are at increased risk for severe and complicated infections.
One specific type of serious illness caused by salmonella is enteric or typhoid fever. Typhoid fever is rare in the United States, causing an estimated 350 cases per year, according to the Centers for Disease Control and Prevention (CDC) in 2023, primarily in people who acquired it in other countries. This disease is caused by the Typhi variety of the Salmonella enterica bacterium. Symptoms during the first week of illness include progressively increasing fever with associated headache, muscle aches, abdominal pains, and lethargy. In the second week, the decreases, the liver and enlarge, small red bumps form on the trunk, and the patient enters into a stupor. During the third to fourth week, intestinal and are common. The fever begins to remit in the fifth to sixth week of illness. Diarrhea usually starts in the first week and resolves within six weeks. Without treatment, death can occur from gastrointestinal hemorrhage and perforation. Infants tend to have much more severe disease than older children.
Salmonellosis caused by nontyphoid salmonella is more common in the United States, causing about 1.35 million reported cases of illness per year according to the CDC in 2024; the number of unreported cases is thought to be far higher. The major of nontyphoid salmonella is the gastrointestinal tract of many animals, including mammals, reptiles, birds, and insects, although plants may also become contaminated. Farm animals and pet reptiles commonly carry salmonella. Some resistance is caused by the use of antibiotics in animal feeds. Contaminated eggs and milk products are common sources of human infection.
Gastroenteritis is the most common disease caused by nontyphoid salmonella. The incubation period for this disease is about one day, with a range from six hours to three days. Symptoms include nausea, vomiting, and abdominal pain. Diarrhea typically contains blood and mucus. Usually, symptoms disappear in less than a week in healthy children, but in young infants and in children with immune deficiencies, symptoms may persist for several weeks.
Bacteremia can occur in 1 to 5 percent of patients with salmonella gastroenteritis. Bacteremia is generally associated with fever, chills, and toxicity in the older child but may be in the infant. Children with an increased risk of include those with acquired immunodeficiency syndrome (AIDS) or other immune deficiencies and hemolytic anemias such as sickle cell anemia.
Bacteremia can lead to infection of almost any organ. Children with sickle cell anemia are more prone to bone infections and meningitis. Salmonella may localize to areas of the body that have received or that contain damaged tissue or a foreign body. Meningitis, of the covering of the and brain, is primarily seen as a of bacteremia in infants. Patients who have persistent bacteremia should also be evaluated for heart infection.
The diagnosis of a salmonella infection is best made by culturing and blood samples. With enteric fever, it is important to culture multiple sites multiple times. Antibiotic susceptibility testing must be performed routinely to guide therapy. Other bacterial causes of can be confused with salmonella infection.
Treatment and Therapy
Treatment for gastroenteritis usually does not require antibiotics. Antibiotics do not speed the resolution of disease but instead lead to prolonged excretion of salmonella. Therapy is primarily focused on the correction of and salt imbalances and on general supportive care. If the patient has indications of sepsis, shock, or chills, however, then antibiotics should be administered. Infants under three months of age and children with immune deficiencies should also be treated with antibiotics. Ampicillin is usually used as the initial treatment in uncomplicated cases, and third-generation cephalosporin antibiotics are used in severe and complicated cases. Some percentage of nontyphoid salmonella in the United States is resistant to ampicillin as well as to other antibiotics. Antibiotic treatment should last ten days to two weeks in children with bacteremia and four to six weeks in children with bone infection or meningitis. Local infections may require surgical drainage.
Typhoid fever is treated for a minimum of two weeks. It is important to perform susceptibility testing for the possibility of resistance so that proper antibiotic therapy can be chosen. Chronic carriers of Salmonella enterica Typhi should be treated with antibiotics. If eradication is unsuccessful, surgical of the biliary tract should be sought.
Prevention of the spread of salmonella requires a number of procedures. Hand washing is critical to the prevention of transmission. Persons who are carriers of salmonella should be excluded from food preparation and childcare settings. Hospitalized infants and children should be isolated. Proper sewage disposal, water purification, and chlorination are essential public health measures. In developing countries, the promotion of prolonged breast-feeding also reduces the infection rate.
There are two typhoid vaccines commercially available in the United States. The first is an oral, live attenuated that requires four doses given over a period of one week and a booster every five years. The second is a capsular polysaccharide vaccine given as a single intramuscular injection and a booster every two years. The vaccines are 50 to 80 percent protective. The live attenuated vaccine should not be given to patients who are pregnant, taking antibiotics, or immunocompromised, such as persons with the Human immunodeficiency virus (HIV).
Perspective and Prospects
Salmonella was identified as the cause of typhoid fever in 1880 and was first cultured in 1884. Since 1920, improvements in sanitation, water supplies, and sewage disposal have resulted in a marked decrease of typhoid fever in the United States. However, it is still a problem in the developing world, where it affects more than 11 to 21 million people per year, according to the CDC in 2024.
Recent research is focused on public health. Measures to decrease food contamination such as improved cleanliness, decreased use of antibiotics in animal feeds, and food irradiation are being evaluated and used to decrease transmission to humans. Research into alternate vaccines with fewer side effects and improved is also being performed.
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