Ch 15: Mechanisms of Pathenogicity

pathogenicity

ability to cause disease

virulence

measurement of severity of disease produced

portal of entry

mucous membranes, skin, parenteral route

ID50

measures pathogenicity of microbe by evaluating the infectious dose for 50% of population to contract a disease

LD50

measures potency of toxin that evaluates the lethal dose to kill 50% of population

adherence

ability to hold on to host cells through adhesions/ligands binding to receptors

direct damage

enzymes disrupt host cell functions and produces waste products or toxins

exoenzymes

secretes outside of cell

coagulate exoenzymes

coagulate blood by binding to surface if bacteria and coats it with fibrin protecting it from phagocytosis

kinases exoenzymes

digest fibrin clots allowing bacteria to escape into circulation and infect other tissues

hyaluronidase exoenzymes

hydrolyses hyaluronic acid that breaks down junctions between cells

collagenase exoenzymes

hydrolyses collagen in tissues to allow bacteria to be more invasive

IgA protease exoenzymes

destroy IgA antibodies in immune system

siderophores

take iron from host binding proteins allowing potential for septicemia

invasins

rearrange acting filaments of host cytoskeleton that promote entry during initial stage of infections

toxins

substances that contribute to pathogenicity and virulence of pathogen

toxigenicity

ability to produce a toxin

antitoxin

antibodies against specifc toxin (passive immunotherapy)

type III (A-B) exotoxin

type of exotoxin that inhibit protein synthesis damaging cell functions

type II exotoxin

type of exotoxin that are membrane disrupting toxins that puncture holes in membranes

type I exotoxin

superantigens that cause intense immune response by releasing intense amount of cytokines from host cells that exacerbate symptoms

endotoxin shock

release of inflammatory cytokines that causes damage to blood vessels, loss of fluid, low BP, fever

endotoxin characteristics

gram (-), present in LPS, lipid A (heat stable), not neutralized by antitoxin, fever, large LD50

exotoxin characterisitics

gram (+), metabolic byproduct of growing cell, protein, neutralized by antitoxin, no fever, small LD50

fungi pathogenic properties

tichothecene toxins inhibit protein synthesis

proteases

capsule prevents phagocytosis + adherence

ergot toxin (LSD like)

aflatoxin - carcinogens

mycotoxin - neurotoxin

algae pathogenic properties

aflatoxin - carcinogens

mycotoxin - neurotoxin

saxitoxin - neurotoxin

protozoa pathogenic properties

avoid host defenses by growing in phagocytes and antigenic variation and proteases

pathogenic properties of helminths

interferes with host function by using host tissue

metabolic waste causes symptoms