A 46-year-old HIV-positive man is hospitalized with fever, cramping abdominal pain, and watery diarrhea. Evaluation shows high fever, hypotension, tachycardia, and lower abdominal distension and tenderness. Abdominal x-ray reveals free intraperitoneal air, and the patient is taken for urgent exploratory laparotomy. Operative findings include an erythematous and dilated colon. A focus of bowel wall necrosis with perforation is resected. Histopathologic analysis reveals acute inflammatory changes, epithelial necrosis, and a layer of denuded epithelium, fibrin, and inflammatory cells overlaying the mucosa. Which of the following pathogens is most likely responsible for this patient's current condition?

Question

A 46-year-old HIV-positive man is hospitalized with fever, cramping abdominal pain, and watery diarrhea.  Evaluation shows high fever, hypotension, tachycardia, and lower abdominal distension and tenderness.  Abdominal x-ray reveals free intraperitoneal air, and the patient is taken for urgent exploratory laparotomy.  Operative findings include an erythematous and dilated colon.  A focus of bowel wall necrosis with perforation is resected.  Histopathologic analysis reveals acute inflammatory changes, epithelial necrosis, and a layer of denuded epithelium, fibrin, and inflammatory cells overlaying the mucosa.  Which of the following pathogens is most likely responsible for this patient's current condition?

Quizplus · Accepted Answer

This patient with diarrhea, abdominal pain, and fever developed a colonic perforation. Given his histologic findings consistent with pseudomembrane formation, this presentation is highly suggestive of Clostridioides difficile infection (CDI) (formerly Clostridium genus). C difficile is an anaerobic, spore-forming, toxigenic, gram-positive rod that causes infectious colitis. The most significant risk factor for the development of CDI is antibiotic use. Antibiotics (particularly clindamycin, fluoroquinolones, and cephalosporins) alter the normal bowel flora, thereby predisposing to C difficile overgrowth. Other risk factors include hospitalization, older age, and proton pump inhibitor use. C difficile produces 2 toxins: Toxin A (enterotoxin) and Toxin B (cytotoxin). These toxins disrupt cellular cytoskeletons and intercellular tight junctions, leading to colonocyte apoptosis. The colonic mucosa responds to toxin exposure by forming yellow-white, patchy pseudomembranes, which consist of a neutrophil-predominant inflammatory infiltrate, fibrin, bacteria, and necrotic epithelium. Patients with severe disease may develop a nonobstructive colonic dilation known as toxic megacolon, which leads to increased risk of colonic perforation (as seen in this patient). (Choice A) Campylobacter jejuni is associated with watery diarrhea that may become bloody, abdominal cramping, and fever. Neutrophilic infiltrate and crypt abscesses are identified on histology. (Choice C) Salmonella typhi causes typhoid fever, which manifests with diarrhea, abdominal pain, high fever, and salmon-colored macules located mainly on the trunk. Histology demonstrates histiocytes, a lymphoplasmacytic inflammatory infiltrate, and associated hemorrhage. (Choice D) Shigella flexneri infection is characterized by sudden onset of severe abdominal cramping, bloody diarrhea, vomiting, and high fever. Cryptitis, ulcerations, and crypt abscesses are identified on histology. (Choice E) Vibrio cholerae causes cholera, which manifests with sudden onset, voluminous, "rice water" diarrhea and vomiting. Histology typically remains normal. Educational objective: Clostridioides (formerly Clostridium) difficile infection is associated with yellow-white, patchy pseudomembranes on the bowel mucosa. These pseudomembranes consist of a neutrophil-predominant inflammatory infiltrate, fibrin, bacteria, and necrotic epithelium. Patients may develop a nonobstructive colonic dilation known as toxic megacolon, which can lead to colonic perforation.

A 46-Year-Old HIV-Positive Man Is Hospitalized with Fever, Cramping Abdominal