Shigella sonnei

Shigella sonnei is the main bacterial pathogen causing shigellosis. These are infectious microorganisms discovered 100 years ago by a Japanese scientist named Shiga, after whom they took their name.

Taxonomy

There are several different classes of Shigella bacteria:

• Shigella sonnei, also known as Shigella of the “D Group”, which causes more than two thirds of all cases of shigelosis in the world.

• Shigella flexnerior Shigella of the “Group B”, causes almost all remaining infections.

• Other type Shigellawhich are rare in the developing world, although they continue to be major causes of disease. A guy in the developing world, Shigella dysenteriaetype 1, causes deadly epidemics of bacilar dysentery.

Infection

A small inoculum (10 to 200 microorganisms) is sufficient to cause infection. The incubation period is from 12 h to 6 days, usually between 2 and 4 days.

Infections with Shigella can be contracted by eating contaminated food that looks and smells normal. Food can be contaminated by contact with infected people who handle it and forget to wash their hands with soap after using the bathroom. Pulses can become contaminated if they are harvested from a field where irrigation is contaminated by fecal residues. Flies can breed in infected feces and then contaminate food. Infections with Shigella can also be acquired by drinking or bathing in contaminated water. Water can become contaminated if it receives sewage or if someone with shigellosis bathes in it.

Types of disease

Most people infected with Shigella develop diarrhea, fever, and stomach cramps within a day or two of exposure to the bacteria. The diarrhea is often bloody. Shigellosis usually resolves in 5 to 7 days. In some people, especially young children and the elderly, diarrhea can be so severe that the patient needs to be hospitalized. An acute infection with high fever may also be accompanied by fits or convulsions in children under 2 years of age.

In addition, Shigella reaches the submucosa of the distal colon and is capable of ulcerating these tissues, but it only produces bacteremia in absolutely exceptional cases. However, by causing colonic involvement, it causes an intense inflammatory reaction with mucus and pus, which can form bleeding ulcers, so the stools are small in volume and may be accompanied by mucus and blood, giving rise, as a whole, to the condition called bacillary dysentery.. S. dysenteriae is the species that usually produces the most serious clinical pictures.

Transferability

Shigellae have humans as their only reservoir and their minimum infective dose is low, which allows their transmission not only through food, but also through water and through direct contact between children in day care centers. Some infected people may not have any symptoms but will still transmit the Shigella bacteria to others. However, like all microorganisms with fecal-oral transmission whose only reservoir is human (shigelas and Salmonella typhi), they can be eradicated with personal and environmental hygiene measures.

Prophylaxis

Infections caused by Shigella continue to be a public health problem on the world scene, being associated with a low standard of living in developing countries and risk groups or people who travel from industrialized countries to places endemic.

There is no vaccine to prevent shigellosis. However, the spread of Shigella from an infected person to others can be stopped by careful and frequent hand washing with soap. It is advisable to use disinfectants such as household bleach or bactericidal liquids after proper hand washing.

People who have shigellosis should not prepare food or serve water to others until they have been shown to no longer carry the Shigella bacteria.

For the food industry, certain measures can be adopted to prevent this disease, such as blanching food, since treated or boiled water prevents the spread of the bacteria; in addition to using fruits and vegetables without skin for the production of processed foods. Or, minimize direct contact of food with hands and cook food intensely and store below 4 °C.