bacterial pathogens and disease II

Question 1

describe gram negative cell wall

Answer 1

lipopolysaccharide = 3 main parts
O polysaccharide

1. repeat units of tri, tetra or pentra saccharide sugars
2. highly variable between species
3. hydrophilic

core polysaccharide

1. ketodeoxyoctanoic acid and heptose
2. relatively constant between species
3. hydrophilic

lipid A

1. phosphorylated glucosamine attached to long chain fatty acids
2. number and type of fatty acids vary by species
3. hydrophobic

Question 2

endotoxin characteristics

Answer 2

endotoxin = lipopolysaccharide
lipid a = active component, not immunogenic
o antigen = highly immunogenic and immune specific
found only in gram negative bacteria
heat stable
not converted to toxoids
major initiator of the sepsis pathway

Question 3

what is sepsis

Answer 3

life threatening organ dysfunction caused by dysregulated host response to infection
driven by innate immune system = macrophages, monocytes, granulocytes, NK cells and dendritic cells
cells detect many pathogen associated molecular patterns and damage associated molecular patterns
detection mediated by cell membrane receptors TLR and c-type lectin and cytosol receptors = NOD/RIG-1 like receptors

effect = proinflammatory cytokines = TNFA, IL1, IL6 or inflammasomes to produce iL6, IL1B cause rapid programmed cell death

Question 4

describe effects of pro-inflammatory cytokines

Answer 4

increase number, lifespan and activation state of innate immune cells

increase adhesion molecule and chemokine expression by endothelial cells
increase acute phase protein e.g. complement
cause fever
cause neutrophil to release extracellular traps made of DNA and antimicrobial proteins that form a scaffold for platelet activation
increase tissue factor expression for blood monocytes
formation of a thrombus

Question 5

describe sepsis resolution

Answer 5

active process
antiinflammatory = IL-10 produced early in process = suppresses production of iL-6 and Y-interferon and stimulates production of soluble TNF receptor and IL-1 receptor antagonist
autophagy of PAMPs and DAMPS removal

damaged cells = undergo apoptosis by englufment by macrophages