Yersinia spp.

Question 1

What three Yersinia spp. are able to cause disease in humans?

Answer 1

1. Y. pestis (plague)
2. Y. enterolitica (gastroenteritis)
3. More rarely, Y. pseudotuberculosis (gastroenteritis)

Question 2

Describe the invasion of Yersinia enterolitica.

Answer 2

1. Attachment: mediated by the adhesins invasin, Ail, and YadA. These bind ECM molecules and cells. Invasin binds beta1-containing integrins with higher affinity than the natural ligand (fibronectin) due to N-terminal homology and two C-terminal cysteines needed for disulphide bond formation. Attachments are made at multiple points and the bacteria are ‘zippered’ inside the cell through cytoskeletal actin rearrangement.
2. Morphological change: the binding of integrins induces their clustering, activating a PTK-containing pathway that leads to actin polymerisation. The bacterium takes advantage of the cells normal ‘spreading’ function and is engulfed as a result. This is seen as a transient pseudopod formation.
3. Intracellular: Y. enterolitica survives within the vacuole and does not reproduce.
4. Invasion: Y. enterolitica resists hagocytosis and the bacterium transverses the epithelium, invading cells on the basolateral surface.

In the body this process is seen in microfold cells (M cells) of Peyer’s patches (small masses of lymphatic tissue found throughout the ileum region of the small intestine)