Human-Microbe Interactions and Pathogenicity

This flashcard set covers the fundamental definitions of human microbiota, sterile body sites, disease-related terminology, and the initial stages of microbial pathogenesis based on lecture notes.

Resident microbiota

Also known as normal microbiota or indigenous microflora, these are microbes that live on selected sites of the human body without causing disease under normal conditions.

Sterile areas

Certain areas of the human body, such as the nervous system, cardiovascular system (blood), and internal organs, that are considered and should be devoid of microbial life.

Blood-brain barrier

A structural impediment with restricted permeability consisting of endothelial cells, astrocytes, and neurons that prevents microbes from entering the nervous system.

Cerebrospinal fluid (CSF)

The fluid found within the meninges that should be sterile in a healthy individual.

Pathology

The scientific study of disease.

Disease

Any condition in which the normal structure or functions of the body are damaged or impaired.

Infection

The successful colonization of a host by a microorganism.

Pathogen

A microorganism that has the capacity to cause disease.

Pathogenicity

The capacity of an organism to cause infection and disease.

True Pathogen

A pathogen capable of causing disease in healthy persons with normal immune defenses.

Opportunistic Pathogen

A microorganism that normally resides in the body without causing disease but can become pathogenic under certain conditions.

Virulence

The degree of pathogenicity of a microbe.

Virulence Factors

Specific characteristics or components of a pathogen that contribute to its capacity to cause disease.

Portal of Entry

The specific route or site, such as the skin, GI tract, or respiratory tract, through which a microbe enters the host's body.

Parenteral Route

A means of entry through the skin barrier via accidental or intentional punctures, such as hypodermic needles or insect bites.

Infectious Dose

The minimum number of microbes needed to cause disease in a host.

Median Infectious Dose ($ID_{50}$)

The number of microbes required to cause infection in $50\%$ of inoculated animals.

Adhesion

The second step of pathogenesis where a microbe binds or attaches to the cells of the human body.

Adhesion Factors

Microbial structures such as fimbriae, glycocalyx (biofilms), viral protein spikes, or adhesive disks used to bind to host cell receptors.