Clinical Syndromes - Shigella

Clinical Syndromes

Shigella spp. cause shigellosis, a clinical syndrome encompassingthe whole spectrum of disease caused by the bacteria. Bacillary dysentery is a severe clinical form of the shigellosis.

Bacillary dysentery: It is an acute gastrointestinal illness mani-fested by fever, vomiting, abdominal cramps, and tenesmus. Incubation period is usually short. It lasts from 12 hours to 7 days, usually 48 hours, and is inversely related to the load of ingested bacilli. The condition manifests with a sudden onset of high-grade fever along with abdominal cramp, tenesmus, urgency, and passage of loose, scanty feces containing frank blood and mucus.

Infection is usually self-limiting. In a small number of patients, asymptomatic colonization of shigellae occurs in the colon, which makes the patient a persistent reservoir for infection. Complications are most often associated with dysenteriae type 1 infection. These include:

·           Arthritis, toxic neuritis, conjunctivitis, and, in children, intussusception.

·           Hemolytic uremic syndrome may also occur follow-ing infection with S. dysenteriae because of vasculopathy mediated by Shiga toxin.

·           Reiter syndrome (arthritis, urethritis, conjunctivitis) is usually observed in adults with HLA-B27 histocompatibility antigen.

·           Shigella septicemia is rare, except in malnourished childrenwith S. dysenteriae infection.

·           Disseminated intravascular coagulation, bronchopneumo-nia, and multiple organ failure may occur in lethal cases of Shigellasepticemia.

In patients with HIV infection, shigellosis is often a protracted, chronic, relapsing disease, even when treated with antibiotics and may be complicated by bacteremia.

S. sonnei causes the mildest form of bacillary dysentery in manypatients; the species may cause only a mild diarrhea. S. flexneri and S. boydii causes more severe illness than that caused by S. sonnei.