Brachyspira pilosicoli

Brachyspira pilosicoli
Phylum	Spirochaetes
Class	Spirochaetes
Order	Spirochaetales
Family	Brachyspiraceae
Genus	Brachyspira
Species	B. pilosicoli

Introduction

Brachyspira pilosicoli is a gram negative spiral shaped obligate anaerobe bacterium, closely related to Brachyspira hyodysenteriae and one of the Spirochaetes family. The bacterium is loosely coiled and is 6-11µm long. It is only weakly haemolytic in contract to B. hyodysenteriae.

The bacterium may have 8-12 flagellae, inserted at each pole of the cell and has a lipopolysaccharide cell wall which also acts as a virulence factor.

This pathogen can also cause zoonotic disease in people.

Lifecycle

Infection of B.pilosicoli is acquired via ingestion of contaminated faeces.

Once in the Alimentary tract, the flagellae allow the bacterium to move through the mucus in the intestine and thus reach and invade its target cells in the large intestine.

The organism remains infective for long periods in organic matter but is inactivated by sunlight.

The pathogen has been isolated from dogs, birds and humans. Dogs are thought to be a source of infection for people.

Pathogenesis

The attachment of B. pilosicoli to epithelial cells of colonic mucosa causes oedema, haemorrhage and leucocyte infiltration, thus disrupting their function and leading to cell exfoliation and malabsorption. The invasion of goblet cells can also lead to secretory diarrhoea.

Toxins and proteins released by B. pilosicoli have haemolytic and cytotoxic effects. Its membranous LPS also contains an endotoxin (lipid A).

Diseases

B. pilosicoli is the cause of porcine intestinal spirochaetosis which is a much milder disease than the Swine Dysentery caused by Brachyspira hyodysenteriae.

Presence of the spirochaetes in grey-pink diarrhoeal faeces is diagnostic.

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References

Hirsh, D. C., Maclachan, N. J., Walker, R. L (19) Veterinary Microbiology. Pp131-133. Wiley-Blackwell, London.