Definitions 1 - Principals of infectious Disease MBI111

Host

organism which provides nutrients, etc. to another organism

Parasite

organism which lives at the expense of (and may even harm) its host; the parasite is generally smaller than the host and is metabolically dependent upon it

Disease

an upset in the homeostasis of the host, resulting in generation of observable changes

Symptom

subjective evidence of damage to the host

Sign

objective evidence of damage to the host

Infectious Disease

one in which detrimental changes in health of the host occur as a result of damage caused by a parasite

Pathogen

microorganism that is capable of causing disease

Virulence

a measure of pathogenicity, which is the ability to cause disease

Virulent

microorganisms that readily cause disease (only small numbers of the microorganism are required to initiate and sustain infection)

Attenuated

microorganisms with reduced ability to cause disease

Avirulent

microorganisms that do not cause disease

Opportunistic

microorganisms that may or may not cause disease generally colonize, but do not infect, the host when usually found associated with a host, called normal microbiota can cause disease if they are inadvertently introduced into a site where they do not usually reside, especially inside host tissues

Present

in every case of the disease (may or may not be present in the healthy host)

Isolated

and grown in pure culture

Cause

when a pure culture is inoculated into a healthy host

Re-isolated

from the host that was inoculated with the pure culture

Contact the host

be transmissible

Colonize the host

adhere to and grow or multiply on host surfaces

Infect the host

proliferate in host cells or tissues

Evade the host defense system

by avoiding contact that will damage it

Damage host tissues

by physical (mechanical) or chemical means

Adhesins

enable parasites to attach to host cells or tissues

Invasins

enable parasites to enter and/or move through host cells or tissues

Evasis

enable parasites to escape from host defenses

Toxins

enable parasites to damage host cells