Explanation

Salmonella species (feces): what is measured?

Salmonella is a bacterium that can cause an intestinal infection. Infection usually happens through contaminated food, such as undercooked eggs, chicken or pork, through raw milk or through contact with animals, including reptiles. According to the LCI guideline (RIVM), a PCR is preferred as the first test; after a positive PCR, a culture follows to type the bacterium and test its sensitivity to antibiotics.

What can it detect?

Salmonellosis: an intestinal infection with diarrhea, abdominal cramps and fever
Typhoid or paratyphoid fever caused by Salmonella Typhi or Paratyphi, a more serious disease that mainly occurs after travel

Result

What does the result mean?

Positive result

A positive result fits an infection with Salmonella. Symptoms usually start within a few days after infection with sudden abdominal cramps, diarrhea, sometimes with blood, and fever, and according to the LCI guideline (RIVM) usually last 3 to 7 days. In young children, older people and people with a weakened immune system, the bacterium can enter the blood. After recovery, adults still shed the bacterium for days to weeks.

Negative result

A negative result means that the pathogen was not found in this stool sample. Some pathogens are shed irregularly, and shortly after infection the pathogen sometimes cannot be detected yet; so an infection is not always ruled out. According to Thuisarts.nl, diarrhea is usually caused by stomach flu; diarrhea that lasts longer than 2 weeks can also have other causes, such as medicines, not tolerating lactose well or an irritable bowel.

After an abnormal result

According to the LCI guideline (RIVM), a mild infection is not treated with antibiotics; drinking enough is the most important. Antibiotics are only needed in a severe infection or a higher risk of complications. A single Salmonella infection is not notifiable, but it is if 2 or more people are ill from the same food; typhoid and paratyphoid fever are always notifiable (group B2). For work with food or in healthcare, work advice may apply.

Reliability

How reliable is the test?

Testing the stool for pathogens that cause intestinal infections is routine testing in Dutch laboratories. According to the LCI guidelines (RIVM), a PCR is preferred over microscopy or culture for most pathogens, because it is more sensitive; a culture is sometimes still needed afterwards to type the bacterium or test its sensitivity to antibiotics. According to Thuisarts.nl, stool testing for diarrhea is mainly useful if you are very ill or if the diarrhea lasts longer than 2 weeks and does not get better; short-term diarrhea is usually caused by stomach flu and usually clears up on its own.

What can affect the result?

Parasites and worm eggs are shed irregularly; one sample can miss an infection, which is why laboratories sometimes ask for samples from several days.
Shortly after infection, the pathogen may not yet be detectable in the stool.
The longer the sample is in transit, the smaller the chance of a positive culture.
A PCR can also find genetic material from a pathogen that is no longer alive or from an infection that has already passed.

Who it is for

Who is the test useful for?

Useful for

According to Thuisarts.nl, stool testing is useful if you are very ill from diarrhea, or if the diarrhea lasts longer than 2 weeks and does not get better, including after travel. In people without symptoms, a positive result says less, because it may fit carriage or an infection that has already passed. Without symptoms, testing is mainly useful if the GGD (municipal public health service) asks for it, for example during an outbreak or because of work in the food sector or in healthcare.

How common is it?

Diarrhea is common and, according to Thuisarts.nl, is usually caused by stomach flu; bacteria and parasites are less often the cause. According to the LCI guidelines (RIVM), a few hundred to over a thousand infections with, for example, Salmonella, Shigella or Cryptosporidium are confirmed by a laboratory in the Netherlands each year, and the real number is much higher because most people are not tested. After travel to a country with poorer hygiene, the chance of a bacterial or parasitic intestinal infection is higher.

LCI guidelines (RIVM) and Thuisarts.nl

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