Microbial Top Facts: Shigella

With a type of the bacteria used in our laboratory for testing, we wanted to shine a light on Shigella in our microbial top facts blog series.

Named after the Japanese scientist, Dr. Kiyoshi Shiga, Shigella was discovered in 1896 during a large epidemic of dysentery in Japan. The genus is divided in to four serogroups with multiple serotypes all of which vary significantly in genetic structure: S. flexneri, S. boydii, S. dysenteriae and S. sonnei, the latter being one of the bacteria that can be tested for at our laboratory. Here are some facts about Shigella you may not know.

Where can we find Shigella

Shigella is found in the stool of infected people, in food or water contaminated by an infected person, and on surfaces that have been touched by infected people.

What makes it thrive

Shigella thrives in the human intestine during infection and is commonly spread both through food and by person-to-person contact. Most Shigella infections are passed through the faecal-oral route. This occurs when basic hygiene and handwashing habits are inadequate.

What can it cause

The infectious dose of Shigella is very low – only a small number of bacterial cells are required to cause an infection. One complication of a Shigella infection is dysentery, a type of gastroenteritis which usually results in blood being excreted in the faeces due to an internal infection. Shigella is responsible for 80-165 million cases of disease and 600k deaths per year worldwide. It is considered far more serious than more commonly known bacteria, such as Salmonella or E. coli because it is becoming resistant to the main drug used to treat the infection it causes.

Why test for it

Shigella is usually spread as a result of poor hygiene or sanitation. Late diagnosis is one of the major causes of human death and spread of the disease, since it limits the effectiveness of control measures that may need to be applied in order to help reduce the spread and cross-contamination of bacteria.