A portal of entry is an anatomic site through which pathogens can pass into host tissue.

Portal of Entry

Pathogens can also enter through a breach in the protective barriers of the skin and mucous membranes. The skin is a natural barrier to pathogens, but breaks in the skin like wounds, insect bites, or needle pricks, can provide a parenteral portal of entry for microorganisms.

Parenteral Route of Entry

An encounter with a potential pathogen is known as exposure or contact. The food we eat and the objects we touch are ways that we can be exposed to potential pathogens. For a pathogen to cause disease, it needs to be able to gain access into host tissue. An anatomic site through which pathogens can pass into host tissue is called a portal of entry. 

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There are four stages of pathogenesis. The pathogen must be able to gain entry to the host, travel to the location where it can establish an infection, evade or overcome the host’s immune response, and cause disease to the host.
- exposure (contact)
- adhesion (colonization)
- invasion
- infection.

Stages of Pathogenesis

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Exposure

Following the initial exposure, the pathogen adheres at the portal of entry. Adhesion refers to the capability of pathogens to attach cells of the body using adhesion factors. Different pathogens use various mechanisms to adhere to the cells of the body.

Adhesion

Once adhesion is successful, invasion can proceed. Invasion involves the wide spread of a pathogen throughout local tissues or the body. Pathogens may produce exoenzymes or toxins, which serve as virulence factors that allow them to colonize and damage host tissues as they spread deeper into the body. 

Invasion

Following invasion, successful multiplication of the pathogen leads to infection. Infection is the final stage of pathogenesis.

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