Final: New material Flashcards
exotoxins
- produces and secreted by bacterium
- specific role in pathogenesis
- may act distant from bacterium
- our bodies produce antitoxin
endotoxin
- a part of the bacterial cell
- LPS
- acts systematically on host
hemolysins
red blood cells
leukocidins
white blood cells
what creates a channel in the membrane
hemolysins and leukocidins
what makes a lot of channels in the membrane
S. aureus and S. pyogenes
A-B subunit toxins
- toxins with two subunits
- toxin produced with subunits together
B subunit
binds cell surface
A subunit
active component
diphtheria toxin
- classic A-B subunit toxin
- transcribed, translated as a single gene unit
- post translational cleavage, reduction to active form performed by host cell
- B subunit binds to cell surface, endocytosed
- in acidic compartment, conformational change creates membrane pore, A subunit enters cytoplasm
- ADP ribosylation of EF-2
Super antigens
- toxins that bind to TCR and MHC activate immune system
- semi specific activation 3-30%
- results in massive overstimulation
medically important exotoxins
- botulinum
- tetanus
- cholera toxin
endotoxins
- LPS-lipopolysaccharide
- Lipid A portion is endotoxin
- released during cell death
- treatment w/ antibiotics may make this worse
- septic shock
- disseminated vascular clotting
- detect with limulus amoebocyte lysate assay
endotoxin induces…
fever and shock
- LPS released when bacteria are lysed in macrophage
- stimulated IL-1, tumor necrosis factor, other cytokines
genetics of pathogenicity
- mobile genetic elements contain toxin genes
- bacteriophage-lysogenic conversion
- plasmids
- transposons
- pathogenicity islands
plasmids and pathogens
toxin genes spread very rapidly
- virulence plasmids can be passed through the population
- tetanus toxin, staph. enterotoxins
lysogenic conversion
- bacteriophage can lyse their host or integrate into chromosome
- lysogens may carry virulence factor genes
- cholera toxin
- SEA
- diphtheria toxin
- botulinum toxin
pathogenicity islands
genomic elements containing virulence genes
- often id by different G+C content from rest of genome
- present in pathogenic strains, absent from avirulent
- potential horizontal transfer unclear
antimicrobial chemotherapy
- based on exploiting differences between our physiology and invading organisms
- antibiotic targets are enzymes or structures essential to pathogens success, but different from our essential parts
which microbe is hardest to treat?
viruses
- may essential parts to them are essential to us. makes it hard to make vaccine
which microbe is easiest to treat?
fungi? bacteria?
sources of antibiotics
natural compounds from bacteria (G+ rods), actinomycetes, fungi
example of a microbe that is very difficult to treat and needs specialized drugs
mycobacteria
bacteriostatic
inhibits growth