Staphylococcus aureus

Fomites

an inanimate object that can hold a pathogen, doorknob, bedding, etc. 

Staphylococcus aureus can cause…

skin infections, boils, impetigo, scalded skin syndrome, abscesses 

Desiccation tolerant

ability of Staphylococcus aureus to survive in extremely dry conditions that would typically be lethal to other bacteria

If systemic it can cause

endocarditis, osteomyelitis, necrotizing fasciitis, necrotizing pneumonia, toxic syndrome, food poisoning

Necrotizing fasciitis/ flesh-eating disease is cause by

exotoxins: Cytolysins, Superantigens, and Exfoliative toxins

Necrotizing fasciitis/ flesh-eating disease does what?

destroy soft tissues and begins and spreads quickly

Necrotizing fasciitis/ flesh-eating disease symptoms

red or purple or black skin, swelling, severe pain, fever, and vomiting

toxins and adhesions are encoded on

lysogenic bacteriophage, plasmids, genomic islands

Three classes of toxins

Cytotoxins (cytolysins), Toxic Enzymes, Superantigens

Cytolysins

pore-forming toxins

Exfoliative Toxin causes what skin syndrome?

Staphylococcal Scalded Skin Syndrome (SSSS) caused by the cleaved of Dsg-1

types of T cell superantigens

Toxic shock syndrome toxin (TSST)

Staphylococcus enterotoxin (SE)

What do T cell superantigens do

Bind to MHC-II and T-cell receptor, simulating antigen presentation this destroy host cells

What is the result of the T cell superantigens

happens in a lot of T cells creating a cytokine storm

Protein A binds to…

the Fc portion of antibodies making them face away from the bacteria which makes them useless

Protein A is released from the cell wall by

there being a failure with stop transfer sequence or the cell wall hydrolases

Protein A is a ____ superantigen

B cell, resembles capping of B cell receptors by antigen and has multiple Ig so it binds to multiple

How is Protein A used in a molecular biology lab

immunoprecipitation/ pull assay

Pull down assay steps

Protein A attached to “Sepharose” beads (agarose beads)

Make rabbit antibodies against a protein of interest

Bind antibodies to the beads

Add cell extract containing antigen and a mixture of other proteins

Centrifuge

Wash the beads a few times

Characterize the cell pellet (find out what co-precipitated with the antigen)

CHIPS

chemotaxis inhibitory protein of Staphylococcus - can inhibit the N-formyl-Met receptor on neutrophils (white cells) and the C5a receptor

S. aureus defend against neutrophils by

lysing them, blocking C5a, detection N-formyl- Met proteins, and the first step in extravasation (when immune cells move out bloodstream)

Coagulase

causes a clot of fibrin to form around cells, protecting them (shield)

Immunothrombosis

Pathogens can be trapped by fibrin clots

Blood clots are formed by

a proteolysis cascade (red) where each protein is activated to end with thrombin converting fibrinogen to fibrin

Coagulase binds 1:1 with Prothrombin, and causes

prothrombin to become active without proteolysis

Staphylokinase

opposes the action of coagulase by dissolving blood clots, which allows the dissemination of bacteria

Fibrinolysis

a cascade that dissolves fibrin clots

Staphylokinase binds 1:1

with Plasminogen, and causes plasminogen to become active without proteolysis. This is more stable and forms Fibrin Degradation Products

Quorum Quenching

Autoinducing peptides from the same strain are agonists

Autoinducing peptides for heterologous strains are potent antagonists.

AgrABCD system

primary quorum sensing mechanism used to regulate its pathogenesis genes based on bacterial population density

two-component system

allowing the bacteria to detect extracellular signals and amplify their response across the entire colony

AgrABCD system

has four proteins:

AgrB (Export and Processing): This membrane protein processes the AgrD precursor and exports the mature AIP into the extracellular space

AgrD (The Pheromone): The precursor for the Autoinducing Peptide (AIP). All AIPs contain a characteristic thiolactone bond between a cysteine and the C-terminus

AgrC (The Receptor): A membrane-bound sensor kinase that detects the concentration of AIP in the environment

A - (Transcription Activator): A response regulator that, once activated by AgrC via phosphorylation, binds to DNA to trigger gene expression

RNAIII

regulates many genes, most positively, a few negatively

AgrABCD expresses

binding proteins at low density and toxins at high density.

coagulase at low cell density and staphylokinase at high cell density