1.4 overcoming host immune response Flashcards
what are virulence factors?
help organism overcome host immune response
can help organism at any stage of infection
4 mechanisms to evade immune system
biofilms
capsules
bacterial toxins
metabolic dormancy
what are biofilms?
many adhesive cells embedded in an ECM and extracellular polymeric substances (EPS)
impenetrable to antibiotics
can become embedded on host material (wounds), or attached to surfaces (catheters)
where are biofilms?
common on prosthetic joints, toothbrush, stainless steel
what is quorum sensing?
regulation of gene expression in response to fluctuations in cell density
bacteria release autoindicers that increase in concentration with cell density
allows cells to communicate with each other to determine if they need to disperse (bc of crowding or nutrients)
stages of biofilm life cycle?
adhesion
accumulation
maturation
dispersion (quorum sensing)
what are capsules?
thick polysaccharide layer (virulence factor)
macrophage cannot engulf
what is toxin production?
small proteins or polysaccharides can arrest cellular functions or lyse host cells
many cellular targets
what are 2 types of bacterial toxins?
endotoxins
exotoxins (enterotoxin, neurotoxin, cytotoxin)
what are endotoxins?
not secreted, liberated when bacteria lyse
LPS on outer memrane of gram-
LPS has core, O antigen, and lipid A
lipid A: heat stable, stimulates immune, can cause septic shock
what are exotoxins?
secreted by bacteria
produced inside gram+
example of endotoxin
salmonella produce macrophage cytotozin
bacteria in macrophage produce toxins that impair function
what is metabolic dormancy?
bacteria can enter dormant state
most antimicrobials only act on metabolically active organisms
ex. SCV of staph aureus can phenotype switch to metabolically quiescent
