Pathogenicity

Pathogenicity refers to the ability of an organism, specifically a microorganism, to cause disease (pathogenesis) in another organism. This ability is determined by the pathogen's virulence factors. The term is often used interchangeably with virulence, but some authors have drawn a distinction between the two.

Overview

Pathogenicity is the quality of causing disease, but the term is most commonly used to describe the degree to which a particular organism is pathogenic. This is often described in terms of the number of organisms required to cause disease in a host organism, with the pathogenicity increasing as the number decreases.

Determinants of Pathogenicity

The pathogenicity of an organism - its ability to cause disease - is determined by its virulence factors. These are characteristics of the organism that enable it to establish itself on or within a host of a particular species and enhance its potential to cause disease. Virulence factors include toxins, enzymes, and adhesion molecules.

Virulence Factors

Virulence factors are molecules produced by bacteria, viruses, fungi, and protozoa that add to their effectiveness and enable them to achieve the following:

• colonization of a niche in the host (this includes attachment to cells)
• immunoevasion, evasion of the host's immune response
• immunosuppression, inhibition of the host's immune response
• entry into and exit out of cells (if the pathogen is an intracellular one)

Pathogenicity vs Virulence

While the terms pathogenicity and virulence are often used interchangeably, some authors have drawn a distinction between the two. They define pathogenicity as the potential capacity to cause disease, while virulence is the degree of pathogenicity within a group or species of parasites as indicated by case fatality rates and/or the ability of the organism to invade the tissues of the host. The virulence of a microorganism's disease is its degree of pathogenicity.

See Also

• Infectivity
• Toxigenicity
• Virulence
• Pathogenesis

References

Pathogenicity Resources
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