Do virulence factors include capsules?

Capsules and Other Surface Components Bacteria have evolved numerous structural and metabolic virulence factors that enhance their survival rate in the host. Capsule formation has long been recognized as a protective mechanism for bacteria (see Ch. 2).

How do capsules contribute to bacterial pathogenicity and virulence?

The capsule is considered a virulence factor because it enhances the ability of bacteria to cause disease (e.g. prevents phagocytosis). The capsule can protect cells from engulfment by eukaryotic cells, such as macrophages. A capsule-specific antibody may be required for phagocytosis to occur.

How do capsules confer bacterial pathogenicity in bacteria?

The capsule is the pathogen’s most important determinant of virulence because it allows the bacterial cells to escape phagocytes in the lung. The B. anthracis capsule is composed of poly-D-glutamic acid. Its capsule is antiphagocytic, and it protects the bacteria from complement- mediated lysis in serum or blood.

What are the five virulence factors of bacteria?

5: Virulence Factors that Promote Colonization

The ability to use motility and other means to contact host cells and disseminate within a host.
The ability to adhere to host cells and resist physical removal.
The ability to invade host cells.
The ability to compete for iron and other nutrients.

What is a capsule in a bacterial cell?

3.2 Capsules. The bacterial capsule is usually a hydrated polysaccharide structure that covers the outer layer of the cell wall, and in most bacteria it is composed of monosaccharides linked together via glycosidic bonds.

What is the most important role of capsule with regards to virulence of a bacteria?

Capsules have a significant role in determining access of certain molecules to the cell membrane, mediating adherence to surfaces, and increasing tolerance of desiccation. Furthermore, capsules of many pathogenic bacteria impair phagocytosis (22, 29, 30) and reduce the action of complement-mediated killing (7, 31, 35).

How might a capsule contribute to pathogenicity How might flagella contribute to pathogenicity?

Flagella contribute to virulence of pathogenic bacteria through chemotaxis, adhesion to and invasion of host surfaces. Flagellin is the structural protein that forms the major portion of flagellar filaments.

How is the capsule formation influenced by environmental conditions?

The size of the capsule is influenced by a variety of host and environmental factors that include host tissue location, CO 2 levels, serum, temperature, and the availability of nutrients such as iron and glucose 10, 12.

Why are the capsules resistant to phagocytic digestion?

Capsules can resist unenhanced attachment by by preventing pathogen-associated molecular patterns or from binding to endocytic pattern-recognition receptors on the surface of the phagocytes. The capsules of some bacteria interfere with the body’s complement pathway defenses.

Why is the capsule considered a virulence factor?

Capsules contain water which protects the bacteria against desiccation. They also exclude bacterial viruses and most hydrophobic toxic materials such as detergents and help the cells to adhere to surfaces. The capsule is considered a virulence factor because it enhances the ability of bacteria to cause disease.