Toxins - Functions Flashcards
Exfoliatin toxin
Staphylococcal scalded skin syndrome
Produced by 5% of S. aureus
Absorbed into bloodstream and causes desquamation of skin
Acute exfoliation of skin following cellulitis
Act on desmosomes causing epidermal splitting
Toxic shock syndrome toxin
Causes toxic shock syndrome
20% of S. aureus produce it
8% mortality rate
Surgical would infections or super absorbant tampons
Fever, hypotension, multi-system shut down, organ failure, toxic shock
What does coagulase do?
Binds to fibrinogen on cell surfaces
This converts fibrinogen to fibrin
This produces fibrin clots
- Causes agglutination of bacterial cells
- Promotes bacterial attachment
- White cells penetrate fibrin clots poorly
What does catalase do
neutralises the production of oxygen free radicals in phagocytes
What does protein A do?
A surface protein
Binds IgG molecules by the Fc region
IgG is bound in he wrong orientation
This disrupts opsonisation and phagocytosis
What are invasins in staph
Degradative enzymes promote spread in tissues
Staphylokinase
Hyaluronidase
Thermostable deoxyribonuclease
What does staphylokinase do?
Dissolves fibrin clots laid down by during inflammation to try to wall of the infection
What does hyaluronidase do
Hydrolyses matrix of connective tissue
What does thermostable deoxyribonuclease do
Releases nutrients for organism
What does Panton-valentine leukocidan do
Produces pores in leukocytes - common in community-associated infection
What does haemolysin do
Produces pores in red blood cell
Staph food poisoning toxin
Produced by 30-50% of S. aureus strains
Heat stable (100 degrees for 10 minutes)
Resistant to gastric and jejunal enzyme
Ingestion cause vomiting, as it acts on the vagus nerve endings in the stomach) and diarrhoea (stimulate intestinal peristalsis)
What do pili do
They adhere to nonciliated mucosal epithelium
Antigenic variation - immune evasion
What does the Opa protein do
Assist in epithelium binding
Assist in antigenic variation and allow for immune evasion
What does iron binding protein do
Facilitates multiplication and colonisation
What does IgA protease do
This cleaves IgA1
Degrades host IgA
What does Por protein do
Forms pores
What does Lipooligosaccharide do
Causes tissue damage
Inhibits mucocillary clearance (nasal infections)
Immune evasion
Antigenic diversity
What do fimbriae do
Attach to nonciliated epithelial cells
Antigenic switching - allows for immune evasion
Bind ciliated epithelium
What does the capsule do
Prominent antiphagocytic polysaccharide
Immune evasion
What is iron acquisition for
Multiplication
What does haemagglutinin do
Attachment to epithelium
Pertussis toxin
Whooping cough
Lymphocytosis
Sensitisation to histamine
Activation of insulin producing causing hypoglycaemia
Dermonecrotic toxin
Vasoconstriction
Ischemic necrosis
Filamentous haemagglutinin
Facilitates attachment of bacteria to ciliated eipthelial cells
Adenyl cyclase toxin
Decreases chemotaxis and phagocytosis of bacteria
Tracheal cytotocin
Inhibits cillia movement and regeneration of damaged cells
Choline binding protein A
(4)
Anchors the protein to the choline residues present in the cell wall
Responsible for remodelling the cell wall
Responsible for adhesion
Promotes invasion
Autolysin LytA
Cell wall degrading protease
responsible for the release of S. pneumoniae virulence factors
Pneumolysin
Cytolytic protein
Released by autolysin
Attacks cell membranes
Proinflammatory
Inhibits PMN
Activates complement
M protein
Surface adhesin
Inhibits phagocytosis
Binds Fc portion of IgG
M types 1, 3, 12 and 28 are the most common isolates found in patients with shock and multiorgan failure
Strains lacking M protein are less virulent
Rheumatic heart disease
T-protein surface antigen
R-protein on some strains
S. pyogenes toxins
(6)
Pyogenic exotoxins
Streptolysin O and S
Streptokinase
C5a peptidase
Streptodornases
Hyaluronidase
Pyrogenic exotoxins
Cause various effects, including the rashes seen in scarlet fever and streptococcal toxic shock disease
Streptolysin O and S
Damages mammalian cells, resulting in cell lysis and release of lysosomal enzymes
Lysis of RBCs, PMNs and platelets
Streptokinase
Catalyses conversion of plasminogen to plasmin, causing lysis of clots, facilitating the rapid spread of organisms
C5a peptidase
Inactivates complement component C5a
Cleaves the chemoattractant C5a
Streptodornase
DNAses degrade the viscous DNA in necrotising tissue or exudates, aiding the spread of infection
Hyaluronidase
Disrupts the organisation of ground substance, facilitating the spread of infection
Breaks down tissue hyaluronic acid
Streptolysin S
Oxygen stable
Not antigenic
Leucocidal action
Streptolysin O
Oxygen labile
Cytotoxic for red blood cells, neutrophils, platelets, cardiac tissue
Responsible for haemolysis that we see on blood agar
SPE-A and SPE-C
Superantigens
Erythrogenic toxins
Similar to staph enterotoxins
Associated with invasive infections and toxic shock syndrome
SPE-B
Cysteine protease
Associated with tissue destruction
Pyocyanin
Interferes with the antioxidant defences in the lung
Facilitates oxidative damage to the lung epithelium
Alginate slime
Matrix of biofilm formation
Impairs cillary function
Elastase
Destruction of elastin
Cleaves IgG, IgA, Complement
Degrades surfactant proteins A and D
Alkaline protease
Lyses fibrin
Phospholipase C
A class of membrane-associated enzymes that cleave phospholipids
Leukocidin
A type of cytotoxin or exotoxin
A pore-forming toxin that kills or destroys white blood cells by creating holes in their membranes
Exotoxin A
A type of cytotoxin or exotoxin
A pore-forming toxin that kills or destroys white blood cells by creating holes in their membranes
Exotoxin S
It impairs the function of phagocytic cells
Four effector proteins of type III secretion system of Pseudomonas
ExoS
ExoT
ExoU
ExoY
ExoU
Rapid destruction of host cell membranes
Is greater in P. aeruginosa isolated in hospital ICUs and burn unit
ExoS
Relevant in patients with CF
