Salmonella Infections

Salmonella infections are caused by one of more than 2,000 strains of a bacterium known as Salmonella.

What is going on in the body?

Salmonella infections occur worldwide. People acquire Salmonella bacteria from one another or from animals. Once the person swallows the bacteria, he or she may develop an infection of the gastrointestinal system known as gastroenteritis. This inflammation of the stomach and intestines commonly causes stomach upset, vomiting, and diarrhea.

Many animals may carry Salmonella bacteria. These include cats, dogs, livestock, fish, birds, rodents, reptiles, and amphibians.

What are the causes and risks of the infection?

Salmonella infections are caused by one of the more than 2,000 strains of the Salmonella bacteria. Salmonella infections are transmitted from animals to people, or from person to person, in the following ways:

The risk of acquiring this infection is increased by the following:

What are the signs and symptoms of the infection?

Most people who develop a Salmonella infection will not have any symptoms. If symptoms do occur, they usually start 12 to 72 hours after contact. Most symptoms last from 4 to 7 days. Diarrhea may last up to 2 weeks. Someone who has a Salmonella infection may have the following symptoms:

Sometimes the bacteria can enter the bloodstream. The bloodstream infection can cause very high fever and low blood pressure. From the bloodstream, the bacteria may spread to other parts of the body. The brain, bones, and other organs may be infected. This often happens in infants with the infection.

Typhoid fever, caused by a specific type of Salmonella known as Salmonella typhi, has a slow onset of symptoms including:

How is the infection diagnosed?

The diagnosis of Salmonella infection starts with a medical history and physical examination. Salmonella organisms can be identified in the stool, blood, urine, or pus of an infected person. In severe cases, they may be found in the cerebrospinal fluid. This is the clear fluid surrounding the brain and spinal cord.

What can be done to prevent the infection?

There are a few ways to help prevent this infection.

Public health measures are important in food processing plants. Outbreaks affecting thousands of people have occurred from a single dirty machine.

What are the long-term effects of the infection?

Salmonella infections usually have no long-term effects. Recovery takes less than a week in most cases. More severe infections are seen in the very young and the very old. People with weak immune systems may also develop more serious infections. In these cases, infections may involve the brain or heart. This can result in death or serious organ damage.

Those who have recovered from an attack of typhoid will have lifelong immunity. Complications of typhoid fever may include:

Some people develop a condition called Reiter syndrome following a Salmonella infection. Reiter syndrome causes joint pain, eye irritation, and painful urination.

What are the risks to others?

A Salmonella infection can easily be spread to others. People caring for children or preparing food should follow the rules of good hygiene.

What are the treatments for the infection?

Healthcare providers suggest that people with mild cases allow the disease to run its course. The main treatment in this case is drinking fluids to prevent dehydration. Some people are not able to keep any liquids down. Such people may need fluids given to them through an IV tube in their arm.

Antibiotics such as trimethoprim-sulfamethoxazole, ciprofloxacin, ampicillin, or gentamicin may be given to certain persons. These include:

What are the side effects of the treatments?

Antibiotics may cause allergic reactions, stomach upset, and rash.

What happens after treatment for the infection?

After a Salmonella infection, people often shed the bacteria in their stools for more than a month. Good hygiene is important to avoid giving the infection to others. Children may be excluded from day care until their stool is clear of the bacteria. Food handlers may be kept off the job until they are no longer carriers.

Three percent of people infected with the Salmonella typhi organism are chronic carriers. This means the organism is in their stool 1 year or more after treatment. They can infect others while having no symptoms themselves. Most carriers are women over the age of 50.

How is the infection monitored?

Any new or worsening symptoms should be reported to the healthcare provider.

Author:Danielle Zerr, MD
Date Written:
Editor:Crist, Gayle P., MS, BA
Edit Date:09/30/01
Reviewer:Eileen McLaughlin, RN, BSN
Date Reviewed:09/04/01