Salmonella infection (salmonellosis) is a common bacterial infection of the intestinal tract. Salmonella typically live in the intestines of animals and humans and are shed through feces, where the bacteria remain highly contagious. Humans become infected most frequently through contaminated food sources, such as poultry, meat and eggs. Typically, people with salmonella infection develop diarrhea, fever and abdominal cramps within 12 to 72 hours. Signs and symptoms of salmonella infection generally last four to seven days. Most healthy people recover without specific treatment. In some cases, diarrhea can be extremely dehydrating and require prompt medical attention. Life-threatening complications may also develop should the infection spread beyond your intestines. our risk of salmonella infection is higher if you travel to countries with poor sanitation. Preventive measures include proper cooking, good hygiene such as hand washing, and avoiding raw or undercooked eggs and meat.
Salmonella infection begins when you ingest one of the various types of salmonella bacteria — with S. enteritidis, S. typhi and S. choleraesuis responsible for most salmonella-related illnesses. Those bacteria that survive the acidic environment of your stomach then travel to your small intestine and adhere to its lining, where they begin their life cycle. Fresh bacteria are shed in your feces, where they remain highly contagious.
You can contract salmonella infection by touching or ingesting anything contaminated with salmonella bacteria. Reservoirs for the microorganism include pet reptiles, dogs and cats, pigs and cattle, infected humans, contaminated water, raw dairy products and chicken eggs. Salmonella can survive for months in water, ice, sewage and frozen meat.
Most frequently, humans come in contact with salmonella through food sources such as contaminated poultry, meat, eggs and egg products.
Methods of salmonella infection include:
- Swallowing or putting something contaminated with salmonella into your mouth
- Drinking water contaminated with salmonella
- Touching contaminated reptiles, including iguanas, turtles or snakes — about 90 percent of reptiles carry salmonella
- Touching contaminated pet rodents
- Eating raw or undercooked food contaminated with salmonella
- Touching your hand to your mouth if your hand has been in contact with a contaminated surface or object
- Having close contact with other infected people or animals — especially their feces — allowing bacteria to be transmitted from your hands to your mouth
In general, salmonella symptoms begin with nausea and vomiting and progress to abdominal pains and diarrhea. Additional signs and symptoms include fever, chills and muscle pains, and can last anywhere from several days to two weeks.
There are more than 2,000 types of salmonella bacteria, although fewer than a dozen types are responsible for most illness in humans. Other symptoms may be present depending on the type of salmonella germ causing your infection. The most prevalent salmonella-related illnesses are:
Gastroenteritis. This increasingly common salmonella-induced illness is caused by the S. enteritidis bacterium, which is most often ingested through raw or undercooked meat, poultry, eggs or egg products. The incubation period ranges from several hours to two days, and additional signs include blood in the stool.
Enteric fever. Also known as typhoid fever, this illness is caused by the S. typhi bacterium and is most commonly contracted by drinking salmonella-contaminated water. The incubation period ranges from five to 21 days following infection. Additional signs and symptoms may include constipation, cough, sore throat, headache and mental confusion. Slightly raised, rose-colored spots on your upper chest also may appear. In addition, a slowing of your heartbeat (bradycardia) and enlargement of your liver and spleen (hepatosplenomegaly) may be present.
Bacteremia. This condition results when salmonella bacteria enter and circulate throughout your bloodstream. Infants and people with compromised immune systems are at special risk of developing serious complications, including infection of tissues surrounding the brain and spinal cord (meningitis) and infection within the bloodstream (sepsis). People with salmonella-induced bacteremia may show few symptoms; however, fever can be present.
If you have intestinal salmonella and you have a healthy immune system, you may not seem ill or show signs or symptoms. However, you may continue to shed the bacteria in your feces and remain contagious for up to a year.
Salmonella infection itself isn’t life-threatening. However, in certain people — especially children, older adults, transplant recipients and people with a weakened immune system — the development of complications can be dangerous.
Complications of salmonella infection may include:
- Reiter’s syndrome — an inflammatory condition characterized by eye irritation, painful urination and painful joints — which can lead to chronic arthritis
- Severe dehydration
- Infection of the tissues surrounding your brain and spinal cord (meningitis)
- Infection of your bloodstream (blood poisoning or septicemia)
- Inflammation of the lining of your heart or valves (endocarditis)
- Infection of your bones or bone marrow (osteomyelitis)
- Spread of infection to other parts of your body
The simplest way to diagnose salmonella infection is to isolate the bacteria in a stool or other culture. Typically, your doctor will ask for a stool sample and send it to a laboratory, where a technician will try to grow and identify the infectious organism under a microscope.
Although salmonella infection elsewhere in your body isn’t always present in your bloodstream, a blood culture might help identify certain types of bacteria and rule out other pathogens.
There’s no reliable treatment for salmonella intestinal infection, and recovery usually depends on the health of your immune system. In most otherwise healthy people, diarrhea and abdominal pains subside within several days to two weeks without specific treatment.
For people with weakened immune systems, the illness can endure and lead to severe diarrhea, fever and significant dehydration and malnutrition. The goal of salmonella treatment is to replace lost fluids, alleviate signs and symptoms, improve your immune response and destroy the invading pathogens. These options include:
Fluid replacement. You’ll need to replace fluids and electrolytes — minerals such as sodium, potassium and calcium that maintain the balance of fluids in your body — lost to persistent diarrhea. This can be done either by drinking lots of liquids, or in cases of serious fluid loss, receiving fluids intravenously. These precautions will help keep your body hydrated and functioning properly.
Dietary modifications. Avoid milk products to help alleviate abdominal pains. Substitute stomach-soothing foods, including bananas, rice, apples and toast.
Antibiotics. If infection has traveled outside your intestine, antibiotic medications can help destroy or inhibit the growth of salmonella bacteria. These drugs include ciprofloxacin (Cipro), a sulfamethoxazole and trimethoprim combination (Bactrim), ceftriaxone (Rocephin) and amoxicillin (Amoxil). Duration of treatment may vary depending on your illness, and range from 14 days for enteric fever to six weeks for bacteremia. Resistance to antibiotics is increasingly reported in various strains of salmonella.
Salmonella infection is contagious, so take precautions to avoid spreading bacteria to others.
Preventive methods are especially important when preparing food or providing care for infants, older adults and people with compromised immune systems.
Follow these suggestions:
- Keep eggs adequately refrigerated (lower than 41 F), and discard cracked or dirty eggs. Avoid keeping eggs unrefrigerated for more than two hours.
- Cook eggs for 15 seconds or more at 145 F. Eat eggs promptly after cooking.
- Avoid eating raw eggs, as in cookie dough, homemade ice cream or eggnog. If you must consume raw eggs, ensure that they have been pasteurized. Check the egg carton or package for labeling.
- Separate uncooked meats from produce and cooked foods to prevent transfer of any bacteria.
- Wash your hands after handling uncooked foods. Also be sure to thoroughly wash cutting boards and utensils.
- Wash your hands after contact with animals, including reptiles, rodents and other pets.
- Wash your hands after handling human and animal feces, including those of household pets.