Which of the following anaerobes is known to cause antimicrobial-associated diarrhea?

Clostridium difficile is recognized as the primary pathogen responsible for antimicrobial-associated diarrhea. This organism is a spore-forming, gram-positive anaerobe that can overgrow in the intestine following the disruption of normal gut flora, often due to antibiotic therapy. The toxins produced by Clostridium difficile can lead to inflammation of the colon, resulting in symptoms such as diarrhea and abdominal pain.

The relationship between antibiotic use and the proliferation of Clostridium difficile is well-documented; antibiotics can diminish the competing microbial population in the gut, facilitating the overgrowth of this particular pathogen. Consequently, the resulting infection, known as Clostridium difficile infection (CDI), is a significant concern in clinical settings, particularly among patients on broad-spectrum antibiotics.

The other choices listed are not commonly associated with antimicrobial-associated diarrhea, as they do not have the same pathogenic mechanisms or prevalence in the context of antibiotic disruption of gut flora.