Pathogens Flashcards
pathogens
microorganisms capable of causing disease
do all species have the same virulence properties?
No and not all strains of a species have disease cause ability
how is a pathogen I identified
set of virulent genes it carries
what is virulence
the measure of the ability to cause harm depending on virulence factors
what factors determine virulence
Invasiveness: the ability of the microorganism to be established in the host
Toxigenicity: the capacity of an organisms to produce substances known as toxins that damage specific tissues in the host
what do pathogens use to invade host tissues
virulence factors : Adhesins: capsules enzymes that destroy host tissues invassins type 3 secretion systems (T3SS) and type 4 secretion system (T4SS)
Adhesins
promote specific attachment to host.
able to attach to one kind or a few kinds and able to determine site of colonization
what do afimbrial adhesins do and give examples of them
Glyco/lipo proteins.
mediate close attachment
caspsules
they prevent the pathogen from being destroyed baby host immune cells
mediates attachment to host cells and other bacteria
streptococcus pneumonias
can also be found in non pathogenic organisms as well
how invasion works
some pathogens use a breach in the skin, wound.
penetration of the mucosa : destruction of the single-cell layer or invasion of cells.
release of extracellular enzymes as a virulence factor
Hyaluronidase: degrades hyaluronic acid, a sticky that holds host cells together.
Collagenase: degrades the protein collagen present in connective tissues
Lecithinase: degrades lecithin (phosphatidylcholine) in the cell membrane and causes lysis of red blood cells.
Gas gangrene
caused by clastodium perfringes which infects a deep wound and uses lecithinase to lyse hose cells and hyaluronidase to break though ECM
hemolysins
cause lysis of red blood cells> some are enzymes and some are cytolysins
leucocidins
cause the lysis of leucocytes. Produced by staphylococci and streptococci.
proteases
degrade complment proteins and other antibodies
coagulase
cause insoluble fibrins to be deposited bacteria surface and this protects them from host immune systems
invasins
surface proteins or injected proteins that allow microorganisms to enter cells
is a ,major virulence factor for intracellular pathogens
protect the bacterial pathogens against the host immune system
examples of microbes that use invasins
mycobacterium, salmonella, Listeria and chlamydia
how to pathogens adapt to to environments in the host cell
they modify properties and behaviour of the host cells
block phagosome maturation ( block digestion)
increase the size of the vacuole
acquire nutrients
block host defenses.
Type 3 and 4 secretion systems
most common in gram neg bac.
T3SS forms a whole in the bacterial cytoplasmic membrane and periplasmic and outer membrane
most common in gram neg bac. T3SS forms a whole in the bacterial cytoplasmic membrane and periplasmic and outer membrane function: invasion of host cells block pathogosome take control of the host
difference between T3SS AND T4SS
The lack of a needle like strructure called injectiosmoes
Toxin
exctracellular enzymes that cause damage
disease categories associated with bacterial pathogens
Infectious disease: result from pathogen growth
intoxication:
result from the presence of a toxin
2 categories of toxins
exotoxin: excreted into surrounding as bacterial pathogen grows
endotoxin: a apart of the bacteria
Exotoxins
these are soluble chemicals that are secreted or rereleased when the organism dies.
usually proteins so they can denatured by heat
highly immunogenic
antibody response inactivates exotoxins
extremely potent
very Lethal
how are toxins categorized
by their target in the host body
name the categories of toxins
neurotoxins enterotoxins nephrotoxins hepatoxins cardiotoxins
AB toxins
modify the host cells and are composed of 2 subunits
enzymatic subunit A:Modifies target inside the host
and binding cell B: binds to specific receptor.
clastridium botulinum
toxin: botulinum
neurotoxin that blocks acetylcholine in neuromuscular junction
flaccid paralysis
how botulism works
blocks the release of A and this blocks the muscle contraction
AB toxin Tetanus toxin
clastridium Tetanii
toxin: TeNT
bacteria lives in soil as spores, can enter a deep would and dissolve into blood stream and affects the neutrons
causing muscle spastic paralysis.
How TeNT works
TeNT bind to inhibitory interneurons that produce glycine and allow the relation of muscle and inhibits their function. results in contraction
AB5 toxins : Cholera toxin
b: binds to intestinal cells
A: acticavates adenylate cyclase leads to the production of CAMP and this blocks Na movement and starts up Cl movement
endotoxins
inside the bacteria
infection by Gram-negative bacteria
Lipid A from LPS layer is released. it is heat stable and activates the immune system
causes fever, shock and diarrhea
vaccines
made with toxins which are firstinactiated with heat or formaldehyde making toxoids which are still antigenic
are there vaccines for endotoxins
no because they can not be in captivated by heat or formaldehyde
pathogenicity island
section of chromosome encoding virulence factor
