When walking her 6-year old son for school, a mother observes that the boy is limping. She notices that his left knee is swollen, red, warm to the touch, and movement is painful. He states he fell on the knee 2 days ago while playing with friends. The mother brings her son to see their pediatrician, who removes 15 ml of cloudy fluid from the knee. A Gram stain and culture of the fluid shows gram-positive cocci arranged in clusters. Further culturing of the specimen on Mannitol Salt agar reveals growth yellow hallow around the colonies. Which organism is most likely the cause of this infection