Invasion

Definition

Invasion is the process by which pathogens enter host tissues and cells, overcoming barriers to establish infection. It is a critical step in the pathogenesis of both bacterial and viral infections.

5 Must Know Facts For Your Next Test

1. Invasion often involves specific virulence factors such as enzymes that degrade host tissues or toxins that disrupt cellular function.
2. Pathogens can invade through various routes, including mucosal surfaces, cuts, and insect bites.
3. Adhesins on the surface of pathogens play a key role in attaching to host cells before invasion.
4. Some bacteria use secretion systems like Type III or Type IV to inject effector proteins into host cells, facilitating invasion.
5. Viruses typically invade by binding to specific receptors on the host cell surface, followed by entry through endocytosis or membrane fusion.

Review Questions

• What are adhesins and how do they contribute to microbial invasion?
• Name two types of secretion systems used by bacteria for invasion and describe their function.
• How do viruses typically invade host cells?

Related terms

Adhesins:

Molecules on the surface of pathogens that help them attach to host cells.

Secretion Systems: Complex protein structures used by bacteria to transport effector molecules into host cells.

Endocytosis:

A cellular process where substances are brought into the cell via engulfment by the cell membrane.