A 4-year-old, previously healthy boy is brought to the emergency department due to fever, abdominal pain, and frequent bloody diarrhea for 2 days. A few children at day care have developed diarrhea over the past week as well. He takes no medications and has not traveled outside the United States. Temperature is 39 C (102.2 F), blood pressure is 110/70 mm Hg, and pulse is 90/min. Physical examination shows increased bowel sounds and left sided abdominal tenderness. Which of the following is the most likely causal organism?

Question

A 4-year-old, previously healthy boy is brought to the emergency department due to fever, abdominal pain, and frequent bloody diarrhea for 2 days.  A few children at day care have developed diarrhea over the past week as well.  He takes no medications and has not traveled outside the United States.  Temperature is 39 C (102.2 F), blood pressure is 110/70 mm Hg, and pulse is 90/min.  Physical examination shows increased bowel sounds and left sided abdominal tenderness.  Which of the following is the most likely causal organism?

Quizplus · Accepted Answer

11ec160b_3808_1d7d_9249_2ff35bf30059_MD0001_00 This child has acute-onset fever, abdominal pain, and diarrhea, findings suggestive of acute bacterial gastroenteritis. Common causative organisms in bacterial gastroenteritis with bloody diarrhea include Escherichia coli O157:H7, Shigella, and Campylobacter. Of the given choices, the most likely pathogen is Shigella sonnei, which is transmitted by ingestion of contaminated food or water. S sonnei is also sometimes implicated in outbreaks in community settings (eg, day care facilities) due to the low infectious dose required for person-to-person spread. Shigella gastroenteritis presents abruptly with high fever, abdominal cramping, and stools that are initially watery before mucus and/or blood appears. Shigella preferentially involves the rectosigmoid region (ie, left-sided abdominal tenderness), causing frequent episodes of small-volume bloody/mucoid diarrhea. Nausea and vomiting are often absent but may occur, and seizure is a severe, uncommon complication that can occur in children. Stool culture is diagnostic. (Choice A) Clostridioides difficile infection most commonly causes profuse, watery diarrhea. This diagnosis is rare without risk factors, such as recent antibiotic use or hospitalization, neither of which is seen in this patient. (Choice B) Clostridium perfringens gastroenteritis, which typically occurs after ingestion of contaminated food (particularly meat) that was inadequately cooked or refrigerated, causes watery, not bloody, diarrhea. (Choice C) Enterotoxigenic Escherichia coli infection is a common cause of watery diarrhea, particularly in resource-limited countries (travelers' diarrhea). In contrast, this patient has bloody diarrhea and no travel history outside the United States. (Choice D) In contrast to nontyphoidal Salmonella gastroenteritis, which can cause bloody diarrhea, Salmonella serovar Typhi infection is most common in resource-limited countries. It causes fever and bacteremia; abdominal pain with or without diarrhea is common but typically begins a week after initial symptoms. This patient's acute-onset bloody diarrhea and lack of travel history make this diagnosis unlikely. Educational objective: Acute-onset bloody diarrhea is most commonly due to Escherichia coli O157:H7, Shigella, or Campylobacter infection. Shigella infection also classically causes high fever and left-sided abdominal tenderness (due to rectosigmoid involvement) and often occurs in outbreaks (eg, day care center). __________ References: Shigella sonnei: virulence and antibiotic resistance. (http://www.ncbi.nlm.nih.gov/pubmed/32929595)

A 4-Year-Old, Previously Healthy Boy Is Brought to the Emergency