An 8-year-old boy is brought to the emergency department due to 2 days of fever, abdominal pain, and diarrhea. The patient has no significant medical history and has received all recommended vaccinations. He attends a primary school and has not traveled recently. The family recently brought home a new puppy from a kennel. The patient's stool is positive for occult blood but negative for ova and parasites. Which of the following is the most likely cause of this patient's symptoms?

Question

An 8-year-old boy is brought to the emergency department due to 2 days of fever, abdominal pain, and diarrhea.  The patient has no significant medical history and has received all recommended vaccinations.  He attends a primary school and has not traveled recently.  The family recently brought home a new puppy from a kennel.  The patient's stool is positive for occult blood but negative for ova and parasites.  Which of the following is the most likely cause of this patient's symptoms?

Quizplus · Accepted Answer

Campylobacter jejuni is a motile, curved, gram-negative rod that is a leading cause of gastroenteritis. The pathogen resides in the gastrointestinal tract of warm-blooded animals and is primarily transmitted to humans due to ingestion of contaminated food, particularly undercooked poultry. However, direct contact with domesticated animals (eg, dogs) is another important source of transmission; puppies from kennels are especially likely to harbor the bacteria. Following ingestion, Campylobacter colonizes the intestinal mucosa, enters enterocytes within endocytic vacuoles, and causes cytotoxic injury due to specific virulence factors (eg, cytolethal distending toxin, lipooligosaccharide). Patients typically develop fever, crampy abdominal pain, and watery diarrhea that may be bloody. Stool studies will show inflammation (leukocytes, erythrocytes) but no ova or parasites; stool culture is diagnostic (enriched media at 42 C [107.6 F] and microaerophilic conditions). Manifestations usually resolve spontaneously in 3-5 days. In a minority of cases, the host response to Campylobacter infection generates cross-reacting antibodies to peripheral nerve myelin gangliosides, leading to Guillain-Barré syndrome. (Choices A and E) Bacillus cereus and Staphylococcus aureus cause enterotoxin-mediated food-borne illness. Ingestion of the preformed toxin leads to rapid-onset nausea, vomiting, and abdominal pain (diarrhea can occur but is usually mild). S aureus food-borne illness is often linked to precooked foods, dairy products, custards, and mayonnaise-based salads; B cereus food-borne illness is often associated with starch-based foods, such as reheated rice. (Choice C) Giardia lamblia is usually transmitted by drinking contaminated water. Foodborne or person-to-person spread may also occur. Giardia typically causes foul-smelling, watery diarrhea that is noninflammatory; therefore, no fecal blood or leukocytes are typically present. In addition, stool ova and parasite testing often reveals Giardia trophozoites or cysts. (Choice D) Norovirus is the most common cause of viral gastroenteritis and is usually transmitted due to food or water contaminated with human feces. Patients typically develop a vomiting-predominant illness with abdominal pain and a moderate amount of watery diarrhea. However, the pathogen is noninflammatory and therefore no stool blood or leukocytes are seen. (Choice F) Vibrio parahaemolyticus lives in marine environments and is typically transmitted via contaminated seafood (eg, shellfish). Manifestations include a diarrhea-predominant gastroenteritis. Life-threatening sepsis can occur in those with liver disease or hemachromatosis. Educational objective: Campylobacter infection is a common cause of gastroenteritis and is typically acquired from contaminated food (eg, undercooked poultry) or domesticated animals (eg, household dogs). Manifestations usually include fever, cramping abdominal pain, and watery diarrhea that may be bloody. Stool studies typically show blood and leukocytes. Campylobacter infection is associated with Guillain-Barré syndrome.

An 8-Year-Old Boy Is Brought to the Emergency Department Due