Clostridioides difficile, formerly known as Clostridium difficile, (C. diff), is a spore-forming, toxin-producing, gram-positive, anaerobic bacterium. It has a spore, rod/spindle shape and is a common bacterium of the human intestine. C diff is considered an anaerobic motile bacterium that is ubiquitous in nature. Microscopically, the bacteria appear as long irregular cells, often drumstick-like or spindle-shaped, with a bulge at the terminal ends. When stressed, the bacteria produce spores that are capable of tolerating extreme conditions. Spores are not typically produced in routine culture.
In approximately 65% of healthy infants and 3% of healthy adults, C diff may be present as part of the normal bacterial flora in the digestive tract. Usually, C diff colonizes the intestinal tract after the normal gut flora has been disrupted. In some individuals, using broad-spectrum antibiotics to treat infections, especially when used over extended periods, can disrupt the balance of the normal flora in the digestive tract. Under these conditions, C diff can produce spores that tend to protect the bacteria from antibiotics. In turn, this can cause an environment in which there is an overgrowth of the C diff bacteria in the colon. The bacteria then begin producing various toxins that can lead to the production of diarrhea and inflammation in the infected individual. An infection of the intestines leading to diarrhea and inflammation caused by the C diff bacteria is termed Clostridioides difficile infection (CDI).
C. difficile colonies on a blood agar plate after 48 hours of growth.
C. difficile, an anaerobic gram-positive rod, is the most frequently identified cause of antibiotic-associated diarrhea (AAD).
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