24.3 Bacterial infections of the gastrointestinal tract  (Page 2/18)

The rapid onset of signs and symptoms helps to diagnose this foodborne illness . Because the bacterium does not need to be present for the toxin to cause symptoms, diagnosis is confirmed by identifying the toxin in a food sample or in biological specimens (feces or vomitus) from the patient. Serological techniques, including ELISA, can also be used to identify the toxin in food samples.

The condition generally resolves relatively quickly, within 24 hours, without treatment. In some cases, supportive treatment in a hospital may be needed.

Shigellosis (bacillary dysentery)

When gastrointestinal illness is associated with the rod-shaped, gram-negative bacterium Shigella , it is called bacillary dysentery , or shigellosis . Infections can be caused by S. dysenteriae , S. flexneri , S. boydii , and/or S. sonnei that colonize the GI tract. Shigellosis can be spread from hand to mouth or through contaminated food and water. Most commonly, it is transmitted through the fecal-oral route.

Shigella bacteria invade intestinal epithelial cells. When taken into a phagosome, they can escape and then live within the cytoplasm of the cell or move to adjacent cells. As the organisms multiply, the epithelium and structures with M cells of the Peyer’s patches in the intestine may become ulcerated and cause loss of fluid. Stomach cramps, fever, and watery diarrhea that may also contain pus, mucus , and/or blood often develop. More severe cases may result in ulceration of the mucosa, dehydration, and rectal bleeding. Additionally, patients may later develop hemolytic uremic syndrome (HUS) , a serious condition in which damaged blood cells build up in the kidneys and may cause kidney failure, or reactive arthritis , a condition in which arthritis develops in multiple joints following infection. Patients may also develop chronic post-infection irritable bowel syndrome (IBS).

S. dysenteriae type 1 is able to produce Shiga toxin , which targets the endothelial cells of small blood vessels in the small and large intestine by binding to a glycosphingolipid. Once inside the endothelial cells, the toxin targets the large ribosomal subunit, thus affecting protein synthesis of these cells. Hemorrhaging and lesions in the colon can result. The toxin can target the kidney’s glomerulus, the blood vessels where filtration of blood in the kidney begins, thus resulting in HUS.

Stool samples, which should be processed promptly, are analyzed using serological or molecular techniques. One common method is to perform immunoassays for S. dysenteriae. (Other methods that can be used to identify Shigella include API test strips, Enterotube systems, or PCR testing. The presence of white blood cells and blood in fecal samples occurs in about 70% of patients Jaya Sureshbabu. “Shigella Infection Workup.” Medscape . Updated Jun 28, 2016. http://emedicine.medscape.com/article/968773-workup. ( [link] ). Severe cases may require antibiotics such as ciprofloxacin and azithromycin , but these must be carefully prescribed because resistance is increasingly common.