الطاعون

Plague is a zoonotic disease caused by Yersinia pestis, a Gram-negative, rod-shaped bacterium.

Wild rodents usually carry these bacteria. Fleas that bite infected rodents can pass the bacteria to humans.

Once inside the host, macrophages engulf Y. pestis.

The bacteria activate stress-response pathways that inhibit phagosome maturation and acidification, allowing bacterial survival and proliferation.

These infected macrophages then migrate to the nearby lymph nodes.

Eventually, the bacteria trigger the apoptosis of infected macrophages, allowing them to escape into the extracellular space.

As the infection progresses, the bacteria utilize a type III secretion system to inject Yersinia outer proteins (Yops) into surrounding immune cells, inhibiting phagocytosis and inducing apoptosis.

At this stage, the bacteria express the F1 antigen, forming an antiphagocytic capsule.

This progression of infection leads to severe inflammation and swelling of the lymph node, characteristic of bubonic plague.