A 79-year-old woman is brought to the emergency department from the nursing home due to explosive diarrhea. Laboratory studies show leukocytosis, and results from a stool specimen return positive for Clostridium difficile toxin genes by polymerase chain reaction. Three days later, one of the nurses who cared for the patient at the nursing home is admitted with diarrhea and is found to have C difficile infection. However, the other nurses who also took care of the patient are asymptomatic and do not develop the infection. If all the nurses were similarly exposed to C difficile, which of the following is the most likely reason that the asymptomatic nurses did not develop the infection?

Question

A 79-year-old woman is brought to the emergency department from the nursing home due to explosive diarrhea.  Laboratory studies show leukocytosis, and results from a stool specimen return positive for Clostridium difficile toxin genes by polymerase chain reaction.  Three days later, one of the nurses who cared for the patient at the nursing home is admitted with diarrhea and is found to have C difficile infection.  However, the other nurses who also took care of the patient are asymptomatic and do not develop the infection.  If all the nurses were similarly exposed to C difficile, which of the following is the most likely reason that the asymptomatic nurses did not develop the infection?

Quizplus · Accepted Answer

Over 400 types of bacteria inhabit the healthy human gastrointestinal tract as part of the normal intestinal microbiome. In healthy humans, these include very few aerobes (eg, Pseudomonas), approximately 10% facultative anaerobes (eg, Escherichia coli, Klebsiella, Lactobacillus, Bacillus), and a majority of strict anaerobes (eg, Bacteroides, Fusobacterium, Clostridium). These intestinal bacteria effectively suppress overgrowth of Clostridium difficile and other potentially pathogenic bacteria by competing for nutrients and adhesion sites within the gut. Antibiotic therapy is the most important risk factor for C difficile infection (CDI) as it can alter the microbiome, leading to a potential overgrowth of pathogenic strains and clinical disease. The organism causes disease by releasing 2 toxins that damage the mucosal lining of the large intestine, leading to diarrhea (toxin A) and necrosis (toxin B) with pseudomembrane formation. (Choice A) Increased risk of CDI is seen with proton pump inhibitor use, suggesting that gastric acidity may have a protective role. The pancreas secretes protease, amylase and lipase, and trypsinogen, among others; however, there is no association between pancreatic enzyme secretion and CDI. (Choice B) Cell-mediated immunity is not essential for prevention of CDI, but it is required to eradicate infections with intracellular agents that avoid the humoral (antibody) immune response (eg, Legionella, Neisseria gonorrhoeae, Listeria monocytogenes, viruses, Leishmania). (Choice C) Individuals usually develop serum antibodies against C difficile toxins, not spores. (Choice E) Rapid gastrointestinal transit is rarely effective at "washing away" pathogenic diarrhea-causing organisms as they are well-adapted to adhering to the gut mucosa in the setting of voluminous diarrhea. Educational objective: In the absence of normal intestinal microbial flora (as may be the case after a course of antibiotics), Clostridium difficile can overgrow and produce enterotoxin (toxin A) and cytotoxin (toxin B). Clinical disease resulting from C difficile overgrowth can range from transient diarrhea to severe pseudomembranous colitis. __________ References: The host immune response to Clostridium difficile infection. (http://www.ncbi.nlm.nih.gov/pubmed/25165542)

A 79-Year-Old Woman Is Brought to the Emergency Department from the Nursing