Staphylococcus aureus: An aerobic gram-positive coccus that produces smooth colonies.  Pigmentation of the colonies may range from gray, gray-white, yellow, yellow-orange or orange.  It produces both free and bound coagulases and hemolysins (exotoxins).  Some isolates produce an epidermolytic toxin that is responsible for the staphylococcal scalded skin syndrome.  Some isolates produce endotoxins which when ingested are responsible for staphylococcal food poisoning.  It can be part of the normal flora of the skin, skin glands, anterior nares, mucous membranes, gastrointestinal tract, and genital tract of humans, warm-blooded  animals, and birds.

 

Clinical Effects of S. aureus infections:

Staphylococcus aureus is an opportunistic pathogen causing a wide range of infections including: furuncles (boils), carbuncles, impetigo, epidermal necrolysis, osteomyelitis, meningitis, endocarditis, pneumonia, mastitis, bacteremia, enterocolitis, staphylococcal food poisoning and toxic shock syndrome.  S. aureus causes a variety of suppurative (pus-forming) infections and toxinoses in humans. It causes superficial skin lesions such as boils, styes and furuncles; more serious infections such as pneumonia, mastitis, phlebitis, meningitis, and urinary tract infections; and deep-seated infections, such as osteomyelitis and endocarditis. S. aureus is a major cause of hospital acquired (nosocomial) infection of surgical wounds and infections associated with indwelling medical devices. S. aureus causes food poisoning by releasing enterotoxins into food, and toxic shock syndrome by release of pyrogenic exotoxins into the blood stream.