Clostridium scindens sp. nov., a Human Intestinal Bacterium with Desmolytic Activity on Corticoids

Clostridium scindens sp. nov., an obligate anaerobe with desmolytic activity, was isolated from human fecal flora. The desmolase, not associated previously with any specific intestinal microorganism, cleaves the carbon-carbon bond of 17-hydroxylated corticoids at C17-C20, thereby converting them to androstans (C19 steroids). In primary cultures on sheep blood agar plates, C. scindens forms minute, nonhemolytic colonies. The gram-positive rods (0.5 to 0.7 by 1 to 2.5 μm) are slightly curved. The rare oval terminal spores (0.8 to 2.0 μm in diameter) are extremely difficult to demonstrate in Gram-stained smears. More than 40% of the cells are fimbriated. Neither a capsule nor flagella are present. d-Fructose, d-glucose, lactose, d-mannose, d-ribose, and d-xylose are fermented. The major fermentation products are acetic acid, ethanol, and hydrogen. The type strain is ATCC 35704 (Bokkenheuser strain 19).