Protein A
Protein A is anchored to staphylococcal peptidoglycan pentaglycine bridges (chains of five glycine residues) by the transpeptidase sortase A. Protein A, an IgG-binding protein, binds to the Fc region of an antibody.
 In fact, studies involving mutation of genes coding for protein A resulted in a lowered virulence of S. aureus as measured by survival in blood, which has led to speculation that protein A-contributed virulence requires binding of antibody Fc regions.

Protein A in various recombinant forms has been used for decades to bind and purify a wide range of antibodies by immunoaffinity chromatography.
 Transpeptidases, such as the sortases responsible for anchoring factors like protein A to the staphylococcal peptidoglycan, are being studied in hopes of developing new antibiotics to target MRSA infections.

Staphylococcal pigments
Some strains of S. aureus are capable of producing staphyloxanthin — a golden-coloured carotenoid pigment.
 This pigment acts as a virulence factor, primarily by being a bacterial antioxidant which helps the microbe evade the reactive oxygen species which the host immune system uses to kill pathogens.

Mutant strains of S. aureus modified to lack staphyloxanthin are less likely to survive incubation with an oxidizing chemical, such as hydrogen peroxide, than pigmented strains.
Mutant colonies are quickly killed when exposed to human neutrophils, while many of the pigmented colonies survive.
In mice, the pigmented strains cause lingering abscesses when inoculated into wounds, whereas wounds infected with the unpigmented strains quickly heal.

These tests suggest the Staphylococcus strains use staphyloxanthin as a defence against the normal human immune system.
 Drugs designed to inhibit the production of staphyloxanthin may weaken the bacterium and renew its susceptibility to antibiotics.
In fact, because of similarities in the pathways for biosynthesis of staphyloxanthin and human cholesterol, a drug developed in the context of cholesterol-lowering therapy was shown to block S. aureus pigmentation and disease progression in a mouse infection model.
Protein A
Protein A is anchored to staphylococcal peptidoglycan pentaglycine bridges (chains of five glycine residues) by the transpeptidase sortase A. Protein A, an IgG-binding protein, binds to the Fc region of an antibody.  In fact, studies involving mutation of genes coding for protein A resulted in a lowered virulence of S. aureus as measured by survival in blood, which has led to speculation that protein A-contributed virulence requires binding of antibody Fc regions.
Protein A in various recombinant forms has been used for decades to bind and purify a wide range of antibodies by immunoaffinity chromatography.  Transpeptidases, such as the sortases responsible for anchoring factors like protein A to the staphylococcal peptidoglycan, are being studied in hopes of developing new antibiotics to target MRSA infections.
Staphylococcal pigments
Some strains of S. aureus are capable of producing staphyloxanthin — a golden-coloured carotenoid pigment.  This pigment acts as a virulence factor, primarily by being a bacterial antioxidant which helps the microbe evade the reactive oxygen species which the host immune system uses to kill pathogens.
Mutant strains of S. aureus modified to lack staphyloxanthin are less likely to survive incubation with an oxidizing chemical, such as hydrogen peroxide, than pigmented strains. Mutant colonies are quickly killed when exposed to human neutrophils, while many of the pigmented colonies survive. In mice, the pigmented strains cause lingering abscesses when inoculated into wounds, whereas wounds infected with the unpigmented strains quickly heal.
These tests suggest the Staphylococcus strains use staphyloxanthin as a defence against the normal human immune system.  Drugs designed to inhibit the production of staphyloxanthin may weaken the bacterium and renew its susceptibility to antibiotics. In fact, because of similarities in the pathways for biosynthesis of staphyloxanthin and human cholesterol, a drug developed in the context of cholesterol-lowering therapy was shown to block S. aureus pigmentation and disease progression in a mouse infection model.
Staphylococcus aureus