Virulence factors

Definition

Virulence factors are molecules produced by pathogens that contribute to the pathogenicity and severity of infections. They help the microorganism invade the host, evade the immune system, and obtain nutrients.

5 Must Know Facts For Your Next Test

1. Virulence factors include toxins, enzymes, and other molecules that assist in pathogen survival and proliferation.
2. Pathogens can acquire virulence factors through horizontal gene transfer, including transformation, transduction, and conjugation.
3. Many virulence factors are encoded on mobile genetic elements such as plasmids or pathogenicity islands within the genome.
4. Examples of virulence factors include adhesins for attachment, invasins for cell entry, and antiphagocytic proteins to evade immune cells.
5. The presence and expression of specific virulence factors are often used to identify and categorize pathogenic strains of bacteria.

Review Questions

• What are virulence factors, and why are they important for pathogens?
• Name three types of molecules that can act as virulence factors.
• How can pathogens acquire new virulence factors?

Related terms

Pathogenicity:

The ability of a microorganism to cause disease in a host.

Horizontal Gene Transfer:

The movement of genetic material between organisms other than by vertical transmission (parent to offspring).

Pathogenicity Island: A distinct class of genomic islands acquired through horizontal gene transfer which contains clusters of genes for virulence.