Explanation

Shigella species (feces): what is measured?

Shigella is a bacterium that can cause inflammation of the large intestine (bacillary dysentery). Infection spreads through stool: from person to person, through contaminated food or water, and also through sex. According to the LCI guideline (RIVM), the laboratory first tests with a PCR; after a positive PCR, a culture follows, but this only succeeds in about a third of samples. The PCR also finds enteroinvasive E. coli (EIEC), a related bacterium that causes the same disease.

What can it detect?

Shigellosis: an intestinal infection with fever, abdominal cramps and diarrhea, sometimes with blood or mucus
An infection without symptoms, which according to the LCI guideline (RIVM) occurs regularly in men who have sex with men

Result

What does the result mean?

Positive result

A positive result fits an infection with Shigella or the related EIEC. Symptoms are fever, abdominal cramps, diarrhea and a constant urge to pass stool without result, sometimes with blood or mucus, and sometimes joint inflammation follows. According to the LCI guideline (RIVM), about half of people get the infection abroad. Shigella is increasingly resistant to antibiotics.

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

Shigellosis is notifiable (group B2): after a positive culture, the laboratory and the doctor report this within 1 working day to the GGD (municipal public health service), which may contact you for source and contact tracing and hygiene advice. According to the LCI guideline (RIVM), a mild infection is not treated with antibiotics; moderately severe to severe illness or a weakened immune system is, preferably based on a sensitivity test. With symptoms, you may not work in the food sector, direct patient care or childcare until you recover, and children do not go to childcare or primary school.

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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