A 5-year-old boy is brought to the emergency department due to diarrhea and a low-grade fever. He attends a day care center where other children developed similar symptoms. The boy has no known medical problems. He is up to date with age-appropriate vaccinations. He has not traveled abroad. Physical examination shows abdominal tenderness on deep palpation but no rigidity. Stool is sent for culture, and the patient is diagnosed with Shigella sonnei infection. The outbreak is reported to public health authorities and is traced to consumption of a potato salad handled by a food worker who recently had a mild diarrheal illness. Which of the following cells are primarily responsible for uptake of the bacteria that initiated the infection in this boy?

Question

A 5-year-old boy is brought to the emergency department due to diarrhea and a low-grade fever.  He attends a day care center where other children developed similar symptoms.  The boy has no known medical problems.  He is up to date with age-appropriate vaccinations.  He has not traveled abroad.  Physical examination shows abdominal tenderness on deep palpation but no rigidity.  Stool is sent for culture, and the patient is diagnosed with Shigella sonnei infection.  The outbreak is reported to public health authorities and is traced to consumption of a potato salad handled by a food worker who recently had a mild diarrheal illness.  Which of the following cells are primarily responsible for uptake of the bacteria that initiated the infection in this boy?

Quizplus · Accepted Answer

Shigellosis is an infectious form of hemorrhagic diarrhea that can be caused by a variety of Shigella species (S dysenteriae, S flexneri, S boydii, S sonnei); shigellosis is most commonly due to S sonnei in industrialized nations (80%). Shigella cannot bind all intestinal cells. Shigella exhibits specificity for the microfold (M) cells at the base of mucosal villi within a Peyer patch region of the ileal mucosa. M cells sample gut lumen contents and transfer antigens to their basal lamina within endosomes. At the base of the cell, macrophages and lymphocytes ready to mount an immune response await within a special pocket (microfold). Shigella penetrates the mucous membrane by passing through M cells via endocytosis. It subsequently lyses the endosome, multiplies, and spreads laterally into other epithelial cells. This results in denuding and ulceration of the mucosa and subsequent leakage of blood, inflammatory elements, and mucus into the intestinal lumen. Patients pass frequent stools mixed with blood and mucus. Stools are frequent and loose due to water absorption inhibition. (Choice A) Endothelial cells form the innermost lining of blood vessels. The Shiga-like toxin of Escherichia coli O157:H7 can cause toxicity to renal endothelial cells, leading to renal insufficiency and uremia. (Choice B) Enteroendocrine cells in the gastrointestinal tract secrete hormones such as somatostatin and cholecystokinin. (Choice C) Goblet cells are responsible for mucus secretion into the gut lumen. Mucus release is increased in inflammatory states; stool will have visible mucus in conditions such as inflammatory diarrhea, giardiasis, and Crohn disease. (Choice E) Paneth cells, which occur in small groups at the base of intestinal crypts, are both phagocytic and secretory, thereby providing first-line immune defense against microorganisms. They secrete lysozyme (an enzyme that dissolves the cell walls of many bacteria) and defensins (polypeptides with antimicrobial properties). (Choice F) In patients with diarrhea, stool is tested for fecal leukocytes (polymorphonuclear cells) when it is unclear whether the etiology is noninflammatory (enterotoxigenic E coli, enteroaggregative E coli, Vibrio cholerae, Clostridium perfringens, Rotavirus) or inflammatory (Shigella, enterohemorrhagic E coli, enteroinvasive E coli, Clostridium difficile, Campylobacter jejuni). Educational objective: Shigellosis is an infectious disease that can be caused by variety of Shigella species; S sonnei is the most common cause of shigellosis in industrialized nations. Shigella invades the gastrointestinal mucosa by gaining access to microfold cells in ileal Peyer patches through endocytosis. Shigella subsequently lyses the endosome and spreads laterally into other epithelial cells, causing cell death and ulceration with hemorrhage and diarrhea.

A 5-Year-Old Boy Is Brought to the Emergency Department Due