Brachyspira pilosicoli

Brachyspira pilosicoli is a Gram-negative, spiral-shaped, obligate anaerobe bacterium. It is a member of the Spirochaete family. The bacterium is loosely coiled and is 6–11 µm long. It has several flagellae, inserted at either pole of the cell, and a lipopolysaccharide cell wall. It causes intestinal spirochaetosis in pigs, but it has also been isolated from dogs, birds and mice. It causes zoonotic infection in humans, with infection thought to originate from dogs. Infection of B. pilosicoli is acquired the faecal-oral route. Once in the alimentary tract, the bacterium invades its target cells in the large intestine causing oedema, haemorrhage and the infiltration by inflammatory cells. The consequences of this are the sloughing of cells into the intestinal lumen, malabsorption and secretory diarrhoea. B. pilosicoli is the cause of porcine intestinal spirochaetosis. The presence of the spirochaetes in grey-pink diarrhoea is diagnostic.