An outbreak of diarrheal illness occurs in a community after a massive hurricane. The affected patients experience voluminous, watery diarrhea that quickly leads to severe dehydration. Stool examinations of these patients yield oxidase-positive, curved, highly motile, gram-negative rods. Epidemiologic study reveals the source as a contaminated water supply. Which of the following patient populations would be most susceptible to developing this illness?

Question

An outbreak of diarrheal illness occurs in a community after a massive hurricane.  The affected patients experience voluminous, watery diarrhea that quickly leads to severe dehydration.  Stool examinations of these patients yield oxidase-positive, curved, highly motile, gram-negative rods.  Epidemiologic study reveals the source as a contaminated water supply.  Which of the following patient populations would be most susceptible to developing this illness?

Quizplus · Accepted Answer

Vibrio cholerae is a comma-shaped, oxidase-positive, highly motile, gram-negative rod that is acquired after ingesting contaminated food or water. The infection is not invasive and does not disseminate outside of the gastrointestinal tract. However, the elaboration of the cholera enterotoxin leads to severe, watery diarrhea that can cause death from electrolyte imbalance and dehydration within 12 hours of symptom onset. Cholera is endemic in southern Asia and parts of Africa and Latin America, where seasonal outbreaks are common (peaks occur prior to and after rainy seasons). In the United States, the disease is rare and occurs mainly in patients who ingest contaminated seafood from the Gulf Coast. V cholerae must survive the acidic environment of the stomach to reach the small intestine and cause disease. Because the organism is very acid-sensitive, a high burden of V cholerae is generally required to cause clinical symptoms (>10¹⁰ organisms from contaminated water or >10⁶ organisms from contaminated food). However, those with inadequate gastric acid production (achlorhydria) can develop the disease with much smaller infectious doses as there is insufficient acid to kill the bacteria. Patients on long-term proton pump inhibitor therapy (eg, omeprazole) have pharmacologically induced achlorhydria; it can also be seen in those with gastritis. (Choice A) Patients with splenectomy are at much higher risk of fulminant infection with encapsulated bacteria such as Streptococcus pneumoniae, Neisseria meningitidis, and Haemophilus influenzae. V cholerae is not encapsulated and not invasive; patients with splenectomy are unlikely to be at greater risk. (Choice C) Recent antibiotic use is a strong risk factor for Clostridium difficile colitis, which typically manifests with watery diarrhea, abdominal pain, and low-grade fever. C difficile is a spore-forming, toxin-producing, gram-positive organism. (Choice D) Patients with chronic liver disease are at increased risk for severe disease with Vibrio vulnificus, which can cause watery diarrhea. However, the ingestion of this pathogen usually leads to severe, rapid-onset sepsis in susceptible patients. In addition, V vulnificus is more likely to cause wound infections than gastroenteritis. (Choice E) Patients with cystic fibrosis are at high risk for infections with Pseudomonas aeruginosa, an oxidase-positive, gram-negative rod. This pathogen is a common cause of pneumonia in this population; it does not cause gastroenteritis outbreaks. Educational objective: Vibrio cholerae must survive the acidic environment of the stomach to reach the small intestine and cause disease. Because the organism is easily destroyed by acid, a high burden of organisms must be ingested to cause infection. However, conditions that decrease gastric acidity (eg, antacid use) lower the minimum infectious dose of V cholerae by multiple orders of magnitude. __________ References: Cholera. (http://www.ncbi.nlm.nih.gov/pubmed/22748592)

An Outbreak of Diarrheal Illness Occurs in a Community After