• General
  • General

What is a salmonella infection?

Written by: Editors

Last update:

Salmonella infection (salmonellosis) is a bacterial disease that affects the intestinal tract.

What is Salmonella?

Salmonella is a type of bacteria named after the American veterinary pathologist Daniel E. Salmon, who first identified the bacteria in 1885. Salmonella outbreaks occur around the world. Salmonella bacteria typically live in the intestines of animals. Eating food infected with Salmonella bacteria can lead to salmonellosis, or salmonella poisoning.

How does salmonella infection occur?

People can get salmonella infection by eating contaminated foods, such as meat, poultry or dairy products (milk and eggs). Infection usually occurs immediately after eating contaminated food. This can cause a variety of symptoms.

The bacteria also spread through contaminated water, or in rare cases, from person to person if hands are not washed properly.

Who is most at risk?

While anyone can get a salmonella infection, young children and people whose immune systems are weakened, such as elderly people or people taking immune-suppressing medications, are more likely to get infected. Travellers to high-risk areas with poor food hygiene practices are also at greater risk for salmonella infection.

What are the symptoms of a salmonella infection?

Salmonella bacteria take 12-48 hours to multiply and trigger a reaction. In the small intestine, Salmonella bacteria produce a toxin which affects intestinal walls, causing salts and sugars and so water to leak out.
In the large intestine, the bacteria cause inflammation of the intestinal walls.

Together, this process causes the typical symptoms of salmonella infection: stomach cramps and watery diarrhoea. Less common symptoms are fever, vomiting and blood/mucus mixed diarrhoea. More rarely, salmonellosis can be invasive with bacteria crossing into the bloodstream infecting other organs such as the joints, lungs, kidneys or spleen.

How can you tell that you have food poisoning?

Diarrhoea is a common symptom of salmonella infection, but it can also be caused by many other things. One important disease to exclude is inflammatory bowel disease in which the stool has blood or mucus mixed in. This is not caused by an infection and requires further investigation.

Examination of stool

Salmonella infection is distinguished from other bacterial causes of diarrhoea like campylobacter and shigella through stool cultures. This involves sending faecal samples in bottles (ideally on three different occasions) to the laboratory for microscopic examination.

How long can you carry Salmonella bacteria in your body?

The presence of Salmonella bacteria confirms the diagnosis. However, it can take some time – even up to eight weeks after symptoms have subsided in a third of all cases – for the bacteria to completely disappear from the stool.

What is the difference between salmonellosis and typhoid fever?

Salmonellosis should be distinguished from typhoid fever and paratyphoid, which are caused by different strains of salmonella. Their typical feature is high fevers rather than diarrhoea. Typhoid fever is more common in tropical countries like India but can be very serious and require immediate treatment and antibiotics.


Symptoms of salmonellosis typically last three to four days. During this time, it is very important to replace the water lost through diarrhoea to avoid dehydration. Although it is better to allow the gut to continue to expel the bacteria through the loose stool, if the diarrhoea is uncontrollable, then Loperamide can be taken.

Should I take antibiotics?

Diarrhoea usually settles down by itself. However, sometimes antibiotics (such as Ciprofloxacin) may be needed if there are signs of salmonella spreading into the bloodstream. Unnecessary use or overuse of antibiotics should be avoided as this can prolong the course of the disease and in some people shift them into being a carrier of the disease.

Antibiotics are also a risk factor for picking up infections because of how they affect the body’s own defences.

Should I wash my clothes?

To avoid spread to others, all clothes and bed sheets should be washed at high temperatures as this is the only way the bacteria are killed. Furthermore, crowds should be avoided for up to 48 hours after symptoms have stopped.

How can I prevent a salmonella infection?

As ever, prevention is better than cure! So, to avoid salmonellosis it is important to take strict hygiene measures when preparing food.

  • Make sure food preparation surfaces are kept clean.
  • Wash animal products thoroughly.
  • Keep them away from other raw food.
  • Always wash your hands thoroughly before and after preparing food.

Proper hygiene plays a critical role in keeping Salmonella bacteria at bay.


© Syed Z Arfeen, Medisch adviseur, juli 2017

All treatments