Staphylococcus Pyogenes Aureus is a non-motile, facultative, anaerobic coccus about 0.8 u in diameter, occurring in groups or singly.

Stains with aqueous solutions of anilin dyes and by Gram's method.

It gives rise to pus-formation and to pyemia.

Culture

On gelatin plates occurs as small orange-colored colonies, which cause liquefaction on the surface. The orange pigment is best seen in the center of the colony. In gelatin puncture it grows as a fine white line, developing its pigment in about three days. Liquefies the gelatin and gives an orange-colored precipitate. On agar there is considerable variation in the color; is rarely golden, commonly yellow, often cream color. Grows as a moist, shining, circumscribed colony; does not liquefy agar. On potato growth is luxuriant. Best temperature, 370 C.

Staphylococcus pyogenes albus is similar in every respect except that it does not produce any pigment.

Staphylococcus epidermidis albus is a micrococcus constantly present in the skin. Thought to be the S. pyogenes albus in an attenuated condition. Similar to the above.

Staphylococcus pyogenes citreus, similar, except that it produces a lemon-yellow pigment.