Staphylococcus aureus (SA)

Characteristics

Gram positive cocci in clusters rapid,

aerobic growth on blood agar

• coagulase positive
• catalase positive
• thermonuclease positive

How is SA transmitted?

They cant penetrated the cutaenuous layer, they can only get in via a breach of the skin.

It is transmitted by person to person contact.

Carried in the anterior nares.

What gives SA the ability to colonize the skin and mucosa surfaces?

• Bacteria Cell surface Proteins ( MSCRAMMs)
• Fibronectin-Binding proteins (Fnbpns A and B)

ENTRY

Entry requires a ______ in the skin. Viral infections put pateints at risk for ______ _______ _______. entry is gained via ________.

Breach;

Secondary bacterial pneumonia;

aspiration

The survival of SA in tissues depends on what factors?

Number is enterin organisms;

Site involvment;

speed with which the body mounts an inflammatory response;

immunological history of the host.

VIRULENCE

What degradative enzymes convert host tissues into nutrients required for bacterial growth?

nucleases;

proteases;

lipases;

hyaluronidase

and

collagenase

VIRULENCE

What cytotoxin causes leukocyte destruction and tissue necrosis?

Penton-Valentine Leukocydin (PVL)

What are 4 oxygen dependent compounds?

Superoxide (O₂-) via NADPH oxidase (from O₂),

H₂O₂ via superoxide dismutase (O₂-),

Activated halidies (Cl-, I-, Br-) via myeloperioxidase; Nitrous oxide

What are some Oxygen-Independent Compounds?

Lysosome (degrades bacterial paptidoglycan);

lactoferrin (chelates iron);

defensisn and other cationic proteins (damage membranes);

Proteases, elastase, cathepsin G

Most staphyloccocal infections lead to the formation of a collection of pus called?

an abccess

When an abccess is forming there is an acute inflammatory reaction, with a rapid and extensive _______ ___ _________?

influx of neutrophils

SA are capable of _______ and ______ many neutrophils that have entered the infection area. These neutophils then _____ ____ ______ _______ ___ lysosomal enzymes, which damage surrounding tissue.

Killing and lysing;

pour out large amounts of

What are some diseases that are caused by SA?

Furuncles, carbuncles, paronychia;

cellulitis;

wound infections