Shigella dysenteriae- Pathogenicity and Clinical Manifestation


Shigella dysenteriae is a type of bacteria that causes a severe form of intestinal infection called shigellosis or bacillary dysentery. Shigellosis is characterized by bloody diarrhea, fever, abdominal cramps, and tenesmus (straining to defecate). Shigellosis can lead to serious complications such as dehydration, sepsis, and hemolytic uremic syndrome (HUS), which is a life-threatening condition that affects the kidneys and blood cells.

Shigella dysenteriae belongs to the genus Shigella, which consists of four species: S. sonnei, S. flexneri, S. boydii, and S. dysenteriae. These bacteria are Gram-negative, non-spore-forming, facultatively anaerobic, and nonmotile rods. They are closely related to Escherichia coli (E. coli) but differ in their ability to invade and replicate in the cells lining the colon.

Shigella dysenteriae is the most virulent species of Shigella and can cause outbreaks of epidemic dysentery in developing countries with poor sanitation and hygiene. It is also the only species that produces an exotoxin called Shiga toxin, which is responsible for the damage to the intestinal epithelium and the renal endothelium. Shiga toxin can also be produced by some strains of E. coli, such as E. coli O157:H7.

Shigella dysenteriae is transmitted by the fecal-oral route, meaning that it can spread through contaminated food, water, surfaces, or direct contact with infected people or animals. It can also be transmitted through sexual contact with someone who has a Shigella infection or who has recently recovered from one. Shigella dysenteriae is highly contagious; it takes only a small number of bacteria (10 to 200) to cause infection.

The incubation period of Shigella dysenteriae ranges from 1 to 3 days after exposure. The duration of the illness varies depending on the severity of the infection and the treatment received, but it usually lasts for 7 days. In some cases, people may develop chronic bowel problems or become asymptomatic carriers of the bacteria after recovery.

Shigella dysenteriae infection can be diagnosed by isolating and identifying the bacteria from stool samples using culture methods or molecular techniques. Antibiotic treatment is recommended for patients with severe shigellosis or those who are at risk of complications or transmission. However, antibiotic resistance is a growing problem among Shigella species, especially S. dysenteriae type 1, which can be resistant to multiple classes of antibiotics. Therefore, prevention measures such as improving sanitation and hygiene, providing safe water and food, and promoting handwashing are essential to control the spread of Shigella dysenteriae infection.