n.
Any of the spherical bacteria that make up the genus Staphylococcus .
The best-known species are present in great numbers on the mucous membranes and skin of all humans and other warm-blooded animals. The cells characteristically group together in grapelike clusters. Staphylococci are gram-positive (see gram stain ) and stationary and do not require oxygen. Of significance to humans is the species S. aureus , an important agent of wound infections, boils, and other human skin infections, and one of the most common causes of food poisoning . It also causes udder inflammation in domestic animals and breast infections in women. The largest cause of hospital infections (accounting for almost 15%), "staph" is often difficult to treat because of its increasing resistance to antibiotics .