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water Identification Shigella dysenteriae is a facultative anaerobic, Gram-negative rod from the family Enterobacteriaceae. S. dysenteriae is primarily a human pathogen, as are all Shigellae. The disease has infected masses, particularly in close living quarters, such as refugee camps. Many prominent figures in history have also succumbed to the disease. President George Washington was known to suffer from recurring bouts of dysentery as early as 1755. During the United States Civil War, physicians would often refer to diarrhea as "diarrhea-dysentery," regardless of its cause. The Union army blamed the disease for more than 50,000 deaths. Shigella dysenteriae type 1 (Sd1) is the only cause of epidemic dysentery [1]. The Shiga bacillus is the most virulent of the four serogroups of Shigella. Laboratory indicators:
Pathogenesis Shigella differs from other members of the family of Enterobacteriaceae in that it has genes that code for epithelial cell invasion and for the production of a potent shiga toxin. The disease is highly communicable. According to some estimates, as few as 10 cells can cause an infection, whereas it can take tens of millions of cholera vibrios to induce disease. The bacterium is spread by fecal-contaminated food or water. Once ingested, the organisms colonize the intestines, then invade the colonic epithelial cells, causing disease. Cell death, tissue destruction, acute inflammation, and ulceration of the mucosa ensues. The Shiga toxin is a potent A-B type toxin with 1-A and 5-B subunits. B subunits bind to the cell and inject the A-subunit. By cleaving a specific adenine residue from the 28S ribosomal RNA in the 60S ribosome, the toxin inhibits protein synthesis, causing cell death. Manifestations The onset time is approximately 12-15 hours. In addition to bloody diarrhea, individuals afflicted with bacillary dysentery experience abdominal cramps, fever, and rectal pain. Severe cases, though uncommon, may advance to include septicemia, seizures, and eventual renal failure. 5-15% of Sd1 cases are fatal. Treatment S. dysenteriae has shown to be more susceptible to antibiotic resistance than other species. Local tests can predict to which antibiotics the bacterium is most sensitive. Ciprofloxacin and ampicillin most are the most frequently administered antibiotics. In the case of dehydration, fluids should be administered orally or, if necessary, intravenously. Prevention Since the bacterium is spread by fecal contamination, infection can usually be avoided by following proper sanitation practices. Maintaining clean water supplies is essential to preventing outbreaks. Additionally, safe food handling methods need to be observed. In the United States, approximately 300,000 cases of shigellosis occur each year. |
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