6. Virulence Factors Flashcards
define virulence
refers to the degree of damage caused by a microbe to its host
what do adhesins bind to
sugar residues in host receptors
what do the pili of neisseria gonorrhoea bind to
galactose
what do the fimbriae of Escherichia coli bind to
mannose
what do flagella (adhesin) bind to
toll-like receptor 5
this is not a glycoprotein
adhesins provide initial attachment, what follows this?
docking with membrane adhesin proteins
what do membrane adhesin proteins bind to
collagen, fibronectin & laminin
what virulence factors ARE quorum-sensing controlled
capsule
invasions
exotoxins
what virulence factors ARE NOT quorum-sensing controlled
adhesins
endotoxins
siderosphores
briefly describe the capsule
polysaccharide layer (mainly composed of alginate), lies outside the cell envelope
involved in attachment, protection from antimicrobials
what do invasins do
act to break down host cells in the immediate vicinity of bacterial growth
what enzymes do invasion’s use to penetrate through epithelium cells
hyaluronidase, neuraminidase, collagenase, coagulase
what produces hyaluronidase
Gram-positives
name two Gram-positive bacteria
streptococci, staphylococci
what does hyaluronidase do
attacks interstitial cement of connective tissues by depolymerising hyaluronic acid
what does collagenase target? how? what produces it?
muscles
breaks down collagen
clostridium
what has longer range: invasins or toxins
toxins - these can be spread around the body
what are endotoxins? when does it become toxic?
the lipopolysaccharide found in the walls of gram negative bacteria, it becomes toxic when the cell wall is damaged and lipid A leaks from the cell wall
once in its toxic state, what effects do lipid A have
- causes host cels to release endogenous pyrogens which target the hypothalamus
- this activates many host systems that cause damage
what is the problem with endotoxins in the pharmaceutical industry
what is the solution?
drugs are filtered for Gram-ve bacteria which can cause lysis = lipid A leakage.
- must be carbon filtered once again to remove endotoxin traces
what bacteria produce exotoxins
both gram+ and gram-ve
name 3 types of exotoxins
cytolytic toxins
A-B toxins
superantigens
describe cytolytic toxins mechanism of action
insert a pore into the membrane or producing enzymes to attack phospholipids
staph aureus Alpha toxin is a cytolytic toxin, how does it work
inserts itself into the host membrane, allowing cell contents to flow out of its pore
