Host Microbe Interactions

from the lecture slides

symbiosis

2 or more species living in contact.

mutualism

symbiosis in which BOTH organisms benefit.

commensalism

sybiosis in which one benefits and one is UNHARMED.

parasitism

symbiosis in ehcih one benefits and one is HARMED.

normal microbiota

group of MOs that routinely colonize the body & gut of a given host, usually don’t cause disease.

microbiome

the community of MOs, as well as their genetic information, in a given environment.

dysbiosis

an imbalance in the microbiome. 

• effects health (physical & mental).

colonization

establishment & growth of microbiome in a particular enviornment.

infection

colonization with a parasitic relationship.

subclinical infection

symptoms do not appear OR too mild to notice.

infectious disease

infection that results in disease.

disease

a condition that prevents the body from functioning normally.

symptoms

the SUBJECTIVE effects experienced by infected individuals. 

signs

the OBJECTIVE evidence of infection.

primary infection

infection in a previously healthy individual.

secondary infection

infection that occurs along with or immediately following another infection, usually the result of the first infection.

pathogen

a disease causing microbe.

primary pathogen

can cause disease in an otherwisely healthy individual.

opportunistic pathogen

(opportunist) causes disease ONLY when the bodys defenses are weakened, or when relatively high numbers of MO are introduced to an unusual site.

virulence

degree of pathogenicity; relative ability of a pathogen to overcome body defeneses and cause disease.

virulence factors

triaits of an MO that specifically allow it to cause disease.

communicable/contagious disease

infectious disease that can be transmitted from one host to another.

infection dose

number of MO sufficent to establish an infection.

ID50

number of MO in which 50& of hosts will be infected.

lethal dose

number of MO to cause DEATH post inoculation

LD50

also used for toxicology (mg toxin/kg body weight).

“The standard measurement in toxicology that indicates the amount of a specific substance or radiation required to kill 50% of a tested population”

incubation period

interval between entrence of pathogen into a host and the onset of illness caused by that pathogen.

illness

period of time during which symptoms & sings of the disease occur.

prodromal phase

a period of vague, early symptoms indicating the onset of disease.

convalesence

period of recuperation & recovery from an ilness.

acute

illness is short term because the pathogen is eliminated by the host’s defenses; person is usually immune to reinfection.

chronic

illness persists over a long period of time.

latent

illness may reoccur if immunity weakens.

localized infection

limited to one area, one site in/on the body.

systemic infection

an infectionous agent that spreads throughout the body.

-emia

(infections) in the blood.

bacteremia

bacteria circulating in the blood stream.

toxemia

presense of toxins circulating in the blood stream.

viremia

viral particles circulating in the blood stream.

adhesins

components of the MO to bind to surfaces

Examples:

• tips of fimbriae 

• capsules or cell wall proteins

Will attach to host cell receptors

• they’re typically GLYCOPROTEINS or GLYCOLIPIDS = sugar providing specificity.

Endotoxins

components of the gram negative cell wall or membranes that can trigger an immune response/system. 

• NOT PROTEINS + heat stable

• example: LPS (lipopolysaccharide)

• can’t be converted into a toxoid

can trigger: 

• sepsis, shock

• DIC (dissemented intravascular coagulation; widespread blood clotting.)

exotoxin

toxic protein produced by the MO, “toxin”

• secreted or leaked from the lysed cell.

antitoxin

“antibody that neutralizes a specific toxin, and it is used as both a natural defense mechanism and a medical treatment.”

suspension of ____ Ab to use as medicine.