A chemotherapy patient with severe diarrhea has anaerobic gram-positive, spore-forming bacilli isolated. What is the correct identification based on the culture results?

The identification of the anaerobic gram-positive, spore-forming bacilli as Clostridium difficile is appropriate in the context described. Clostridium difficile is well-known for its association with antibiotic use and chemotherapy, which can disrupt normal gut flora and lead to overgrowth of this opportunistic pathogen. The symptoms of severe diarrhea are a hallmark of C. difficile infection, often referred to as antibiotic-associated diarrhea or pseudomembranous colitis.

C. difficile produces toxins that can damage the intestinal lining, leading to diarrhea and potentially severe complications. Its spore-forming capability allows it to survive in harsh environments and contributes to its transmission and persistence in healthcare settings. Invoking the history of chemotherapy, which is frequently associated with immunosuppression and the disruption of normal gut bacteria, further supports this identification.

Other members of the Clostridium genus, such as Clostridium perfringens, Clostridium tetani, and Clostridium sordellii, are associated with different clinical conditions unrelated to the context of antibiotic use and diarrhea. Therefore, the specific isolation of C. difficile given the symptomology of severe diarrhea aligns perfectly with the clinical scenario provided.