A 38-year-old woman comes to the emergency department due to abdominal discomfort and diarrhea. Her symptoms began after she returned yesterday from a Caribbean cruise. She consumed bottled water but ate raw, local seafood when visiting one of the islands. The cruise line has reported no other passengers with abdominal illness. On examination, the abdomen is soft with mild, generalized tenderness and hyperactive bowel sounds. A comma-shaped, oxidase-positive, gram-negative rod naturally found in salt water is implicated in her illness. Stool microscopy is most likely to demonstrate which of the following findings?

Question

A 38-year-old woman comes to the emergency department due to abdominal discomfort and diarrhea.  Her symptoms began after she returned yesterday from a Caribbean cruise.  She consumed bottled water but ate raw, local seafood when visiting one of the islands.  The cruise line has reported no other passengers with abdominal illness.  On examination, the abdomen is soft with mild, generalized tenderness and hyperactive bowel sounds.  A comma-shaped, oxidase-positive, gram-negative rod naturally found in salt water is implicated in her illness.  Stool microscopy is most likely to demonstrate which of the following findings?

Quizplus · Accepted Answer

11ec160b_3818_bf65_9249_b7e7a87e6903_MD0001_00 Vibrio cholerae is an oxidase-positive, gram-negative, comma-shaped organism that requires salt for growth and exists naturally in aquatic environments. Transmission occurs due to ingestion of contaminated food or water. Sporadic cases are often caused by the consumption of contaminated shellfish; outbreaks may occur in areas where safe water, sanitation, and health care services are limited. Pathogens typically cause diarrhea by invading/damaging the intestinal epithelium or releasing enterotoxins. V cholerae is a noninvasive organism. It clumps together in colonies along the surface of the small intestine and causes diarrhea via the elaboration of cholera toxin (related to enterotoxigenic Escherichia coli heat-labile toxin). This enterotoxin enters intestinal epithelial cells and activates adenylate cyclase, leading to increased chloride efflux, reduced sodium reabsorption, and the subsequent movement of water from the enterocyte to the gastrointestinal lumen. Patients typically present with high-volume, watery diarrhea that can cause dehydration and death within 12 hours. Because the pathogen is noninvasive and the toxin does not cause cell death, stool microscopy generally reveals no leukocytes or erythrocytes. However, flecks of mucus are often seen (rice-water stool) due to the activation of goblet cells. Aggressive fluid resuscitation is the mainstay of therapy. (Choice A) Charcot-Leyden crystals (from eosinophil breakdown) in the stool are sometimes seen in intestinal parasitic infections. Diarrhea with peripheral eosinophilia can be seen with Strongyloides, Ancylostoma, Ascaris, Toxocara, and Trichinella (but not with Giardia or Entamoeba). (Choice B) The presence of leukocytes with monocytic predominance is typical for typhoid fever caused by Salmonella Typhi. (Choices C and D) Invading bacteria that cause dysentery or inflammatory diarrhea (eg, Shigella species, Salmonella species, Campylobacter jejuni, enteroinvasive E coli [EIEC]) are usually marked by leukocytes with neutrophilic predominance and erythrocytes. A hemorrhagic organism (eg, enterohemorrhagic E coli O157:H7, which causes toxin-mediated enterocyte death and intestinal hemorrhage without mucosal invasion) would be characterized by erythrocytes without leukocytes. Educational objective: Vibrio cholerae and enterotoxigenic Escherichia coli cause a purely toxin-mediated watery diarrhea. The toxins secreted by these organisms modify electrolyte handling by enterocytes but do not cause cell death; therefore, no erythrocytes or leukocytes are typically noted on stool microscopy. __________ References: Laboratory diagnosis of bacterial gastroenteritis. (http://www.ncbi.nlm.nih.gov/pubmed/25567220) Complexity of rice-water stool from patients with Vibrio cholerae plays a role in the transmission of infectious diarrhea. (http://www.ncbi.nlm.nih.gov/pubmed/18024592)

A 38-Year-Old Woman Comes to the Emergency Department Due to Abdominal