<I>Shigella</I>

Shigella

Shigella is a Gram-negative bacterium that causes a spectrum of intestinal disease in humans. The majority of infections occur in children ages 1-4 years old - the "hands in the mouth" ages. This germ can be a real problem in group child care settings.

The incubation period varies from 1 to 7 days but is usually 2 to 4 days. The mildest form of disease consists of loose stools for a few days, with little else in the way of symptoms. Patients with small bowel involvement with the germ can have a sudden onset of fever, systemic toxic effects, headache, and a profuse, watery diarrhea. Seizures can occur, triggered by a toxin released by the germ. In fact, sometimes the seizure is the first manifestation of illness in a previously healthy child with no seizure history in the past. The mystery is solved when the child subsequently has a large diarrhea stool, which subsequently tests positive for Shigella bacteria.

Infection of the large intestine produces a fairly classic picture of abdominal cramps, tenderness, straining to have a stool even though not much is produced (tenesmus), and mucousy stools with or without blood (bacillary dysentery).

Feces of infected persons are the source of infection (the fecal-oral route). Animals do not harbor this germ. Transmission of Shigella can occur by ingestion of a very small amount of material - literally a fly-speck. Hence flies are an important route of transmission; a single fly-speck can contain enough bacteria to produce illness. Eating or drinking contaminated food or water or contact with a contaminated toy or other object also are important modes of transmission of the disease.

Patients are thus contagious until the germ is no longer present in the feces. Even without antibiotic treatment, the carrier state usually ceases within 4 weeks of the beginning of illness. A chronic carrier state is rare, which differentiates Shigella from Salmonella infections. Again in contrast to the management of Salmonella infections, symptomatic patients with Shigella infections are treated with antibiotics.

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