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Virulence Factors

Virulence factors are the properties of an organism that enable it to cause infection. This can be due to its ability to evade host defenses or to use the body's nutrients. Virulence factors are often encoded by genes that are close to each other on the bacterial chromosome, forming 'pathogenicity islands'.

Virulence factors include:

colonization factors (fimbriae, adhesins, biofilms): allow bacteria to stick to cells or devices

antiphagocytic mechanisms (capsule, protein A): prevent flashlights

exotoxins: enzymes and toxic proteins that are excreted by bacteria

endotoxin (ie pyrogens): LPS is found in the outer membrane of gram negative bacteria and released following destruction of bacteria. It acts on macrophages and B cells, causing a release of cytokines (which ones)?. This causes fever, low blood pressure, vasodilation, and increased vascular permeability (toxic shock)

invasive substances: often degradative enzymes

Gene Transfer

DNA can be transferred on plasmids through direct conjugation, ediated by pili. DNA can also be transferred by bacterophages in a process called transduction.