M2 Basis of Infectious Disease Flashcards
Define the term Gram-negative bacteria
bacteria which has only 1-3 layers of peptidoglycan but has a lipopolysaccharide outer layer
Define the term Gram-positive bacteria
bacteria which has many multiple layers of peptidoglycan
Role of outer membrane of gram negative bacteria in sepsis
lipopolysaccharides, aka bacterial endotoxin
Explain the term pathogenesis
the ability of endogenous bacteria to shift to a parasitic lifecycle through adaptation
What is bacterial adhesion?
The adhesion of bacterial ligands to adhere to receptors on the host’s cells
What are the 5 things that bacteria must do to evade host defences?
- Immunity at mucosal surfaces
- Destroy immune cells
- Interfere with inflammatory response
- Evade innate immunity
- overome acquired immunity
Give the main features of a bacterial capsule
- secreted layer external to outer membrane and cell wall
- is a polysaccharide layer
- immunogenic
Give 3 abilities that bacterial capsules have to fight immune response
- interfere with deposition of complement
- can mask antibodies
- composition can mimic host
Explain the term acquired immunity
immunity through memory pretty much
Give the 2 ways that bacteria can overcome acquired immunity
Phase variation
Antigenic variation
Explain Phase variation
switching between on and off to control a gene
Explain Antigenic variation
allows the bacterium to change the sequence of a gene
Give an example of a bacteria that uses Phase variation
Salmonella
Give an example of a bacteria that uses Antigenic variation
Neisseria gonorrhoeae Pili
Give the 6 ways in which infection can spread
superficial systemic extracellular intracellular general contact injection
Give the 2 methods of bacterial intracellular invasion
Zipper mechanism
Trigger mechanism
how does the zipper mechanism of bacterial intracellular invasion work?
through ligand binding and membrane engulfment
how does the trigger mechanism of bacterial intracellular invasion work?
through T3SS needles on the bacteria injecting into the cell membrane
If the bacteria penetrates blood vessel endothelium, what is the result?
bacteria circulate in blood
If the bacteria penetrates phagocytic cells, what is the result?
bacteria establish new sites of infection
If the bacteria penetrates lymphatic tissue endothelium, what is the result?
bacteria accumulate in lymph nodes
what are the basic building blocks of a lipopolysaccharide?
Lipid A
Core polysaccharide
O-antigen
what is the main role of lipopolysaccharides on the outer membrane of gram-negative bacteria?
to bind to receptors on macrophages, B cells and other cells that stimulates release of acute phase inflammatory cytokines
what is 1 main symptom of sepsis?
fever
Explain the term spore and give an example
inert structures, resistant to physical and chemical challenge, e.g. C difficile
What type of bacteria is Clostridium spp.?
Gram positive, anaerobic
Where is Clostridium spp. found?
found in faeces and soil
What does Clostridium spp. produce?
Spores that can survive outside the body for many months and can cause severe tissue damage
Give 3 infections that are caused by Clostridium spp.
Diarrhoea - antibiotic associated
Gangerene
Tetanus
Explain the term biofilm
a complex community of bacteria found on surfaces e.g. hard surfaces of the mouth
