Pathogenicity Flashcards
Pathogenicity
ability to cause disease
virulence
the degree of pathogenicity
steps microbe must take to cause disease/infection
- enter organism
- adhere to tissues
3.penetrate the tissues - damage cells to establish disease
(evade immune system)
Portals of entry
mucous membrane, skin, parental route (cuts),
-don’t necessarily cause disease at this point
ID50
infectious dose for 50% of sample population
LD50
lethal dose for 50% of population
Adherence
adhesins/ligands bind to receptors on host cells
- adhesins on glycocalyx, fimbriae, pili, flagella
- adhesions are typically glycoproteins or lipoproteins
- receptors are usually sugar detectors
- biofilms
- glycocalyx capsules
antigenic variateion
pathogens alter their surface antigens
glycocalyx
prevents phagocytosis
helps with adherence
can be antigenic
invasins
- surface proteins produced by bacteria that rearrange actin filaments of cytoskeleton, causing membrane ruffling in host cells
- some use actin to propel themselves
- some can survive inside phagocytosis or escape before lysosomal fusion or prevent lysosomal fusion
virulence factors
molecules produced by bacteria
-coagulases, kinases, hyaluronidase, collagenase, IgA proteases
coagulases
coagulate fibrinogen
-clotted blood protects bacteria from phagocytosis
kinases
digest fibrin clots to sneak into cells
hyaluronidase
digest polysacchrides that hold cell together
collagenase
breaks down collagen
IgA proteases
destroy IgA antibodies
four methods to damage cell
- use host nutrients
- 2. direct damage in immediate area - toxin production that’re transported to damage far sites
- hypersensitivity reactions (allergic reactions)
using host’s nutrients
siderophores = proteins secreted by pathogens that bind iron better than host cells
direct damage
disrupts host cell’s function
produces waste products
multiplies in host cells and cause ruptures
toxins
poisonous substances produced by microbes –> fever, heart problems, diarrhea and shock
toxigenicity
ability of microbe to produce a toxin
intoxication
presence of toxin without microbial growth (e.g. food poisoning)
toxemia
presence of toxins in blood
exotoxin
proteins produced inside cell and secreted out
- reusable, so a little goes a long way
- may act at far site
- antigenic
- very specific
- destroy host cells or stop host’s functions
antitoxin
antibodies against specific exotoxins (usually injected)
toxoids
inactivated exotoxins used in vaccines
AB exotoxin
contains enzyme component (A) and binding component (B)
-Diptheria toxin and typhoid toxin
B binds to host cell and causes endocytosis
-A exits endosome and does damage while B leaves cell
superantigens
cause intense immune response due to release of cytokines from host cells (T cells)
-nausea, vomiting, diarrhea, shock, death
genotoxins
damage DNA, causing mutations, disrupting cell division, leading to cancer
Endotoxins
Part of the cell, not a metabolic product
-Lipid A portion of LPS in G- bacteria
-released during bacterial multipulcation or death
-stimulate macrophages to release cytokines in high concentrations
-make hypothalamus produce prostaglandins to increase body temp
-
Endotoxins and septic shock
- shock = life threatening decrease in blood pressure
- caused by cytokines
- damages capillaries
portals of exit
respiratory tract - coughing and sneezing
gastrointestinal tract - feces and saliva
genitourinary tract - urin and genital secretions
skin
blood - arthropods that bite + needles
saliva
