What is Salmonellosis?
Salmonella infections occur when people come into contact with the bacteria salmonella, which is often found in the intestines of birds, reptiles and mammals, as well as in feces of both humans and animals.
Anything that comes into contact with an infected animal's intestines or feces can transmit the bacteria, which can then develop into a salmonella infection (called salmonellosis). In most cases, people ingest salmonella through contaminated food or water. Also, most cases of food contamination are not evident – contaminated foods usually look and smell normal.
Salmonella bacteria enter the body through the mouth then travel into the stomach and intestines. After salmonella has entered the body, it may be hours or days before symptoms of infection occur. During this time, bacteria attach to the intestinal wall, where they multiply.
The presence of salmonella bacteria in the intestines causes gastroenteritis (also known as "food poisoning"), in which the intestines become irritated and their normal function is disrupted. This, in turn, causes symptoms such as diarrhea, vomiting, abdominal pain and cramping.
In most cases, a salmonella infection resolves on its own and does not cause any serious complications. Gastric fluid normally present in the body kills some bacteria, helping to regulate the amount of bacteria in the intestines. Peristalsis (muscle contractions that keep contents moving through the digestive tract) helps to flush bacteria from the intestines.
Although most cases of salmonellosis usually resolve on their own, complications can occur. For instance, patients who experience severe diarrhea may become dehydrated. In people with poor health or weakened immune systems, salmonella can penetrate through the mucosal lining of the intestines, enter the bloodstream (bacteremia) and cause life-threatening infections. In rare cases, salmonella infection can lead to Reiter's syndrome (inflammation and pain of the joints, eye and urinary tract). Chronic arthritis may result.
Some people infected with salmonella do not develop symptoms, but instead become carriers and spread the infection through close contact with others
Salmonella infection is one of the most common types of foodborne illnesses. According to estimates by the Centers for Disease Control and Prevention (CDC), there are approximately 40,000 cases of salmonella infection reported each year. However, most cases of salmonella infection are mild, and therefore never diagnosed by a physician or reported to health agencies. The CDC estimates the actual number of infections to be more than 30 times greater than the number reported (about 1.4 million cases of the most common form of salmonellosis). Of the 40,000 reported cases of infection, about 15,000 result in hospitalizations and an estimated 500 result in death each year.
More than 2,000 different types (serotypes) of salmonella exist that can affect humans, according to the CDC. They are generally divided into the following categories:
Non-typhoidal salmonellaThis type of salmonella can infect a wide variety of animals as well as humans. There are estimated to be 1.4 million non-typhoidal salmonella infections every year in the United States, according to the CDC. The five most common non-typhoidal serotypes are:
- S. Typhimurium
- S. Enteritidis
- S. Newport
- S. Javiana
- S. Heidelberg
Typhoidal salmonellaThis type of salmonella only infects humans and is transmitted via contaminated human feces. Typhoidal salmonella causes gastroenteritis as well as enteric fever (also known as typhoid fever), which includes symptoms of diarrhea accompanied by a rash on the abdomen and chest. Fewer than 500 cases of enteric fever are reported in the United States each year. Most cases are the result of exposure while in developing countries (e.g., Southeast Asia, India, Africa, South America). Typhoidal salmonella serotypes include:
- S. Typhi
- S. Paratyphi
How is it diagnosed?
Diagnosis of a salmonellosis begins with a visit to a physician for a physical examination and medical history. This may include a discussion of current medications, recently-consumed foods and the duration and extent of symptoms. It may also include any other information (e.g., recent travel, restaurants visited) that may be relevant to the contraction of a foodborne illness such as a salmonella infection.
Many different conditions can cause the symptoms commonly seen with a salmonella infection. In order to identify a salmonellosis as the cause of symptoms, patients may need to undergo fecal tests or blood tests, including a complete blood count. Examination of a sample of patient's feces or blood under a microscope can identify the presence of salmonella bacteria in a patient's body. Salmonella is usually identified after culturing the stool for one or two days.
After an infection, salmonella may continue to be passed in a patient's stool for one to two months. A small percentage of patients continue to pass the bacteria in their stool for at least one year. They become known as carriers because they may infect others but show no symptoms themselves.
The occurrence and possible spread of salmonella infection is a significant public health concern. Because of this, physicians and laboratories are required to report confirmed cases of salmonellosis to local or state health departments. These agencies report to the Centers for Disease Control and Prevention (CDC), which monitors the frequency of salmonella infection in the United States.
In addition, local and state health departments may investigate outbreaks (when two or more people get sick from the same source). This can help locate the source and prevent the spread of a salmonella infection. For example, public health officials may contact people recently diagnosed with a salmonella infection to ask about recent restaurants visited, foods eaten and where those foods were purchased. They may also contact people who ate at a suspected source (e.g., restaurant, catered event) but did not get sick, in order to identify which specific food may have been the source of infection.
How is Salmonella infection treated?
In the majority of cases, a salmonella infection usually resolves on its own within four to seven days. Most people with a salmonellosis do not require treatment.
Patients with a salmonellosis need to drink plenty of fluids and electrolytes (substances necessary for proper bodily chemistry and function, such as salt) to avoid dehydration. Increasing fluid intake is particularly important for children because they become dehydrated faster than adults. Small amounts of clear liquids are recommended. Soft drinks, tea, coffee, fruit juice and sports drinks should be avoided because they do not replace electrolytes appropriately.
Patients with a salmonella infection should switch to a bland diet for the duration of their illness to avoid aggravating any existing nausea. After the diarrhea, nausea and vomiting subside, patients can gradually reintroduce solid foods into their diet. This can include foods that help relieve diarrhea (e.g., bananas, rice, applesauce, toast) and foods that are easy to digest (e.g., chicken noodle soup). Foods that can aggravate diarrhea and should be avoided include high-fat and high-fiber foods, as well as any food product (including chewing gum) that contains the sugar substitute sorbitol.
Severe cases of salmonellosis may require hospitalization. In these cases, patients may receive fluids intravenously. They may be given antidiarrheal medications to ease diarrhea or antiemetics to treat nausea or vomiting. Non-aspirin pain relievers (e.g., acetaminophen) may be taken to reduce symptoms of fever, abdominal pain and cramping.
Patients are rarely given antibiotics to treat a salmonella infection. Most cases of salmonella do not respond to antibiotic treatment. In addition, antibiotics may prevent the quick expulsion of the bacteria, keeping salmonella within the intestines for longer periods of time.
Antibiotics are used, however, when the infection travels outside the intestines via the bloodstream (e.g., bacteremia) or in cases of a typhoidal infection (usually caused by exposure to contaminants in developing countries).
Antibiotics may also be used when there is a high risk of medical complications as a result of salmonella infection, such as in the following populations:
- Infants (3 months old and younger)
- Elderly (50 years old and older)
- Patients with immune system deficiencies (e.g., patients with HIV, cancer)
Stay in bed, except for trips to the bathroom, until at least 3 days after diarrhea, fever and other symptoms disappear. Then resume normal activities gradually. Flex the legs regularly in bed to prevent formation of blood clots.
Drink diluted electrolyte solutions, such as Gatorade or Pedialyte, until diarrhea stops. Then eat a bland but high-calorie, well-balanced diet. Vitamin and mineral supplements may be helpful after prolonged illness.
What might complicate it?
Complications include severe dehydration, shock, or collapse. Septicemia, a life-threatening illness, can occur when bacteria multiply rapidly in the blood stream.
Salmonellosis is usually a self-limited disease, meaning that most cases resolve within 48 to 72 hours. This may be life threatening in immunocompromised individuals.
Conditions with similar symptoms include inflammatory bowel disease, irritable bowel syndrome, or other forms of infective gastroenteritis.
Internist and infectious disease specialist.
Seek Medical Attention
- An infant has symptoms of a Salmonella infection and shows signs of dehydration, such as dry, wrinkled skin, decreased urination or dark urine.
- You or a family member has symptoms of aSalmonella infection that persist longer than 48 hours.
- The following occur during the illness: Fever of 102° F (38.9° C) or higher, jaundice (yellow skin or eyes), cough with blood, or worsening diarrhea.
Last updated 30 June 2015