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1-فاکتورهای بیماریزادراستافیلوکوکوس آرئوس چی هستن؟
در رابطه با این سوال میتوانید به متن انگلیسی زیر مراجعه کنید که به طور کامل در این باره توضیح داده
2-ژن های مقاومت آنتی بیوتیکی دراستافیلوکوکوس آرئوس؟
ژن*های qac A/B، smr،bla Z و mec AStaphylococcus Aureus Virulence Factors
Toxins
Depending on the strain, Staphylococcus aureus is capable of secreting several toxins, which can be categorized into three groups. Many of these toxins are associated with specific diseases.
Pyrogenic toxin superantigens
(PTSAgs) have superantigen activities that induce toxic shock syndrome (TSS). This group includes the toxin TSST-1, which causes TSS associated with tampon use. The staphylococcal enterotoxins, which cause a form of food poisoning, are included in this group.
Exfoliative toxins
EF toxins are implicated in the disease staphylococcal scalded-skin syndrome (SSSS), which occurs most commonly in infants and young children. It also may occur as epidemics in hospital nurseries. The protease activity of the exfoliative toxins causes peeling of the skin observed with SSSS.
Other toxins
Staphylococcal toxins that act on cell membranes include alpha-toxin, beta-toxin, delta-toxin, and several bicomponent toxins. The bicomponent toxin Panton-Valentine leukocidin (PVL) is associated with severe necrotizing pneumonia in children. The genes encoding the components of PVL are encoded on a bacteriophage found in community-associated MRSA strains.
Protein A
''Protein A'' is a protein that is anchored to staphylococcal peptidoglycan pentaglycine bridges by the transpeptidase Sortase A. Protein A is an IgG-binding protein which 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, and this 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 which are responsible for anchoring factors like Protein A to the staphylococcal peptidoglycan are being studied in hopes of developing new antibiotics to target MRSA infections.
Role of pigment in virulence
Some strains of ''S. aureus'' are capable of producing ''staphyloxanthin'' - a carotenoid pigment that acts as a virulence factor. Its has an antioxidant action that helps the microbe to evade killing with reactive oxygen used by the host immune system. It is thought that staphyloxanthin is responsible for S. aureus' characteristic golden colour. When comparing a normal strain of ''S. aureus'' with a strain modified to lack the yellow coloration, the pigmented strain was more likely to survive dousing with an oxidizing chemical such as hydrogen peroxide than the mutant strain was.
Colonies of the two strains were also exposed to human neutrophils. The mutant colonies quickly succumbed while many of the pigmented colonies survived. Wounds on mice were swiped with the two strains. The pigmented strains created lingering abscesses. Wounds with the unpigmented strains healed quickly.
These tests suggest that the yellow pigment may be key to the ability of ''S. aureus'' to survive immune system attacks. Drugs designed to inhibit the bacterium's production of the staphyloxanthin may weaken it 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.