Shigella dysenteriae Shigella dysenteriae

Shigella dysenteriae appearance

  • Gram-negative rods with rounded ends
  • nonmotile
  • non-spore-forming

Infections caused by Shigella dysenteriae

S. dysenteriae, spread by contaminated water and food, causes the most severe dysentery because of its potent and deadly Shiga toxin. Contamination is often caused by bacteria on unwashed hands during food preparation, or soiled hands reaching the mouth. The most commonly observed signs associated with Shigella dysentery include colitis, malnutrition, rectal prolapse, tenesmus, reactive arthritis, and central nervous system problems. Further, S. dysenteriae is associated with the development of hemolytic uremic syndrome, which includes anemia, thrombocytopenia, and renal failure (Wikipedia).


Shigellosis is an infectious disease caused by a group of bacteria called Shigella. Most who are infected with Shigella develop diarrhea, fever, and stomach cramps starting a day or two after they are exposed to the bacteria. The diarrhea is often bloody. Shigellosis usually resolves in 5 to 7 days. Persons with shigellosis in the United States rarely require hospitalization. A severe infection with high fever may be associated with seizures in children less than 2 years old. Some persons who are infected may have no symptoms at all, but may still pass the Shigella bacteria to others.

There are several different kinds of Shigella bacteria: Shigella sonnei, also known as "Group D" Shigella, accounts for over two-thirds of shigellosis in the United States. Shigella flexneri, or "group B" Shigella, accounts for almost all the rest. Other types of Shigella are rare in this country, though they continue to be important causes of disease in the developing world. One type found in the developing world, Shigella dysenteriae type 1, can cause deadly epidemics (CDC).

Shigella infections treatment
Should be always guided by in vitro susceptibility tests!!

Persons with mild infections usually recover quickly without antibiotic treatment. However, appropriate antibiotic treatment may shorten the duration of illness and decrease the spread of infection. Antibiotic treatment is recommended for patients with severe disease, bloody diarrhea, or compromised immune systems (CDC).

  • ampicillin
  • trimethoprim-sulfamethoxazole
  • Resistance to these traditional first-line drugs is common.

  • fluoroquinolones
  • ceftriaxone
  • azithromycin

  • List of antibiotics

some antidiarrheal agents can make the illness worse and should be avoided (see CDC recommendations)




Colony appearance

Shigella dysenteriae morphology S.dysenteriae bacteria morphology Shigella dysenteriae