Microbiology and Immunology

WORLD OF MICROBIOLOGY AND IMMUNOLOGY Dysentery

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infection is weathered, the symptoms will subside within

approximately two weeks.

Adults experience a less severe course of disease. They

will initially feel a griping pain in the abdomen, develop diar-

rhea, though without any blood in the stool at first. Blood and

pus will appear soon, however, as episodes of diarrhea recur

with increasing frequency. Dysentery usually ends in the adult

within four to eight days in mild cases, and up to six weeks in

severe infections.

Shigella dysenteriaebrings about a particularly virulent

infection that can be fatal within 12 to 24 hours. The patient

has little or no diarrhea, but experiences delirium, convul-

sions, and lapses into a coma. Fortunately, infection with this

species is uncommon.

Treatment of the patient with dysentery usually is by

fluid therapy to replace the liquid and electrolytes lost in

sweating and diarrhea. Antibioticsmay be used, but some

Shigella species have developed resistance to them, and in

these cases, antibiotics may be relatively ineffective.

Some individuals harbor the bacterium without having

symptoms. Like those who are convalescent from the disease,

the carriers without symptoms can spread the disease. This

may occur by someone with improperly washed hands prepar-

ing food, which becomes infected with the organism.

Another form of dysentery called amebic dysenteryor

intestinal amebiasis is spread by a protozoan, Entamoeba his-

tolytica.The protozoan occurs in an active form, which infects

the bowel, and an encysted form, which forms the source of

infection. If the patient develops diarrhea, the active form of

amoeba will pass from the bowel and rapidly die. If no diarrhea

is present, the amoeba will form a hard cyst about itself and

pass from the bowel to be picked up by another victim. Once

ingested, it will lose its shell and begin the infectious cycle.

Amebic dysentery can be waterborne, so anyone drinking

infested water that is not purified is susceptible to infection.

Amebic dysentery is common in the tropics and rela-

tively rare in temperate climates. Infection may be so subtle as

to be practically unnoticed. Intermittent bouts of diarrhea,

abdominal pain, flatulence, and cramping mark the onset of

infection. Spread of infection may occur with the organisms

entering the liver, so abdominal tenderness may occur over the

area of the liver. Because the amoeba invades the lining of the

colon, some bleeding may occur, and in severe infections, the

patient may require blood transfusions to replace lost blood.

Treatment, again, is aimed at replacement of lost fluids

and the relief of symptoms. Microscopic examination of the

stool will reveal the active protozoan or its cysts. Special med-

Dysentery epidemic amongst Hutu refugees.

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