S. aureus Bacteria of the genus Staphylococcus are gram-positive cocci that are microscopically observed as individual organisms, in pairs, and in irregular, grapelike clusters.The cell wall contains peptidoglycan and teichoic acid. The organisms optimal growth is at 37 degrees (body temp) and are resistant to temperatures as high as 60°C, to high salt concentrations, and to drying. Colonies are usually large (6-8 mm in diameter), smooth, and translucent. The colonies of most strains are pigmented, ranging from cream-yellow to orange. S. aureus is considered most resistant of all non-spore forming bacteria, which also lack flagella. About 80,000 deaths per year in the U.S. are associted to staph infections.







Enzymes of S. aureus (Virulence factor-makes it more harmful)
1. Coagulase-causes clotting, if a staph produces coagulase it is S. aureus.
Coagulase test converts fibrinogen to fibrin.
2. Hyaluronidase- digest hyaluronic( the cement between cells)
3. Penicillinase and other enzymes deactivate drugs, by breaking down the bata-lactam ring


Exotoxins of S. aureus
1. Blood cell toxin-hemolysin and leuocidin
2. Intestinal toxin- Staphylococcal food poisoning is due to the absorption of staphylococcal
enterotoxins preformed in the food.
3. Exfoliative toxin- cause epidermal layer to slough off germs.
4. Toxic shock syndrome.

* 20-60% of adults carry S. aureus n their nasal carriage because it is a salty envirpment.

MRSA (methicillin-resistant staph aureus)
The symptoms of MRSA depend on where you're infected. Most often, it causes mild infections on the skin, causing pimples or boils. But it can also cause more serious skin infections or infect surgical wounds, the bloodstream, the lungs, or the urinary tract.MRSA is spread by contact. So you could get MRSA by touching another person who has it on the skin. Or you could get it by touching objects that have the bacteria on them.




Miscellaneous systemic Infection
Systemic infections from staph show a focal pattern starting form a localized infection.
* Osteomyelitis- is an infection within the bone tissue that can cause a break or even death.
* Pneumonia form aspirating Staph can cause fever, chest pain and lung abscesses.
* Endocarditis can destroy heart valves.

Host Defenses against S. aureus
You have a well developed resistance to staph infections. Our main defence is phagocytic response with neutrophils and macrophages.