Which of the following statements about acute infectious diarrhea are true: (a) In patients with acquired immunodeficiency syndrome, enterotoxigenic Escherichia coli are the most common pathogens; (b) Dysentery is characterized by acute diarrhea accompanied by abdominal pain; (c) Microscopic examination of a fresh stool sample is very useful; (d) Colonoscopy is essential; (e) Differential diagnosis must include antibiotic‑associated colitis?

Acute Infectious Diarrhea: Statement Analysis

Direct Answer to Each Statement

Statement (b) is TRUE: Dysentery is characterized by acute diarrhea accompanied by abdominal pain. 1 Additionally, statement (c) regarding microscopic examination and statement (e) regarding differential diagnosis with antibiotic-associated colitis are also TRUE. Statements (a) and (d) are FALSE.

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Detailed Analysis of Each Statement

Statement (a): FALSE - Enterotoxigenic E. coli in AIDS patients

Enterotoxigenic E. coli are NOT the most common pathogens in AIDS patients with diarrhea. 1

• The actual most common pathogens in AIDS patients with persistent diarrhea include: Cryptosporidium, Cyclospora, Cystoisospora, microsporidia, Mycobacterium avium complex, and cytomegalovirus 1
• AIDS patients with persistent diarrhea require additional testing beyond routine bacterial cultures specifically for these opportunistic organisms 1
• A broad differential diagnosis is mandatory in immunocompromised people with diarrhea, especially those with moderate and severe primary or secondary immune deficiencies 1

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Statement (b): TRUE - Dysentery characteristics

Dysentery is indeed characterized by acute diarrhea accompanied by abdominal pain, along with fever and bloody stools. 1, 2

• Classic presentation includes: Fever, bloody or mucoid stools, and severe abdominal cramping or tenderness 1
• The combination of loose stools, abdominal pain, and high-grade fever most strongly suggests acute bacterial gastroenteritis, particularly invasive pathogens like Campylobacter, Salmonella, Shigella, or Yersinia 2
• These invasive bacterial enteropathogens characteristically cause inflammatory diarrhea with this constellation of symptoms 2, 3

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Statement (c): TRUE - Microscopic examination utility

Microscopic examination of fresh stool samples is very useful, though with important caveats. 1

• Fresh stool is preferred for identification of viral and protozoal agents, and C. difficile toxin 1
• A diarrheal stool sample (one that takes the shape of the container) is the optimal specimen for laboratory diagnosis 1
• However, fecal leukocyte examination should NOT be used to establish the cause of acute infectious diarrhea (strong recommendation) 1
• Fecal leukocyte morphology degrades during transport and processing, making accurate recognition difficult, and they are intermittently present and unevenly distributed in stool, limiting sensitivity 1
• Despite this limitation, microscopic examination for parasites remains valuable, particularly in persistent diarrhea >7 days 4

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Statement (d): FALSE - Colonoscopy is NOT essential

Colonoscopy is NOT essential for routine acute infectious diarrhea diagnosis. 1

• Endoscopy or proctoscopic examination should be considered only in specific circumstances: 1
  • People with persistent, unexplained diarrhea who have AIDS 1
  • People with certain underlying medical conditions 1
  • People with acute diarrhea with clinical colitis or proctitis 1
  • People with persistent diarrhea who engage in anal intercourse 1
• Duodenal aspirate may be considered in select people for diagnosis of suspected Giardia, Strongyloides, Cystoisospora, or microsporidia infection 1
• The vast majority of acute infectious diarrhea cases are diagnosed through stool testing, not endoscopy 1

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Statement (e): TRUE - Differential diagnosis with antibiotic-associated colitis

Differential diagnosis must absolutely include antibiotic-associated colitis (C. difficile). 1

• Testing for C. difficile should be considered in: 1
  • People >2 years of age with a history of diarrhea following antimicrobial use 1
  • People with healthcare-associated diarrhea 1
  • People with persistent diarrhea without an etiology and without recognized risk factors 1
• C. difficile testing is indicated if antibiotic use occurred within the preceding 8-12 weeks 5, 2
• A single diarrheal stool specimen is recommended for detection of toxin or toxigenic organism 1
• This is a critical pitfall to avoid: Missing C. difficile in healthcare-associated diarrhea or recent antibiotic exposure 2

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Key Clinical Pitfalls to Avoid

• Never give empiric antibiotics for suspected STEC O157 or Shiga toxin 2-producing STEC due to increased risk of hemolytic uremic syndrome 5, 2, 3
• Do not rely solely on fecal leukocyte examination to establish infectious etiology 1
• Do not perform routine colonoscopy for uncomplicated acute infectious diarrhea 1
• Always consider C. difficile in patients with recent antibiotic exposure (within 8-12 weeks) 5, 2
• Remember that STEC characteristically presents WITHOUT fever despite causing severe abdominal pain and bloody stools 4, 5, 2