The correct answer is B. This patient is experiencing C. difficile colitis, also known as pseudomembranous colitis. This type of diarrhea is common in hospitalized patients; at least 30% of hospitalized patients are colonized with the organism. Certain antibiotics have a predilection for causing C. difficile colitis: clindamycin, ampicillin, amoxicillin, and cephalosporins have a high incidence of causing this infection but it can be linked with any of the antibiotics. These antibiotics suppress normal gut flora, allowing Clostridium to proliferate. Two endotoxins (A and B) cause the symptoms and the colonic pathology noted in the vignette. Diagnosis is made by identifying stool containing C. difficile toxin. ; Sigmoidoscopy also provides additional diagnostic information, particularly the presence of plaques (also called pseudomembranes). Treatment is oral metronidazole or vancomycin. Surgery is sometimes indicated for recurrences that are unresponsive to therapy or when complications such as toxic megacolon occur.
B. cereus (choice A) is a spore-forming gram-negative rod that causes diarrhea similar to that seen with C. difficile colitis. It is usually associated with food poisoning, however, particularly on reheated grain foodstuffs (such as fried rice). Treatment is symptomatic. Patients who have this pathogen develop nausea and vomiting within 6 hour of ingestion of this pathogen, and this is followed by diarrhea. There is no fever associated with this.
E. coli 0157:H7 (choice C) causes severe abdominal pain and severe bloody diarrhea. It is usually obtained by consumption of raw beef or unprocessed milk. This organism also has been implicated in hemolytic-uremic syndrome, a potentially deadly syndrome involving hemolysis and kidney failure. For hemolytic uremic syndrome to develop, the patient typically must be treated with antibiotics after ingestion of this pathogen. Shiga-like toxins cause direct damage to renal glomerular endothelial cells, which lead to the kidney damage. Treatment usually involves parenteral antibiotics.
Shigella (choice D) species cause fever, cramps, and diarrhea that can be watery but later develop into bloody, mucus-containing stools. It is usually obtained by poor hygiene, infected food, and transmission by flies. Children attending daycare are the most likely to acquire this condition. Treatment is symptomatic if mild, oral fluoroquinolones or trimethoprim-sulfamethoxazole if more severe.
The symptoms of Y. enterocolitica (choice E) infection are almost identical to those of Salmonella. Yersinia is typically acquired by ingestion of contaminated pork, beef, milk, or cheese. If it is associated with abdominal pain, the pain is classically located in the right lower quadrant, as this pathogen has a predilection for the cecum and terminal ileum. It is also known to cause mesenteric adenitis. Treatment is symptomatic. This condition is sometimes mistaken for appendicitis..
PEARL: The 2 main risk factors for Clostridium difficile colitis are recent antibiotic use (which disrupts the normal bowel flora and allows this native pathogen to replicate unchecked) and recent hospitalization (which increases risk for acquiring this pathogen, primarily because of poor handwashing techniques). Patients who have this pathogen typically present with diarrhea, abdominal pain, and leukocytosis. There may also be associated fever, abdominal tenderness, and abdominal distention. Identification of the stool cytotoxin tissue culture assay is diagnostic. Identification is usually done by stool enzyme immunoassay for toxins A and B. Patients may also have + fecal occult blood testing on the stool, but this is not specific for the diagnosis. Diagnosis can also be made via sigmoidoscopy or colonoscopy because of its classic appearance with pseudomembranes. Treatment involves discontinuing the antibiotic and administering oral metronidazole (Flagyl) or vancomycin.
Clostridium difficile can survive on the skin when using antibacterial gel for hand hygiene so the recommendation is to use hand washing with soap and water to prevent transmission to others.
