Staphylococci are a group of Gram-positive bacteria that are members of the genus Staphylococcus. Several infections are caused by staphylococci. In particular, infections associated with methicillin-resistant Staphylococcus aureus are an increasing problem in hospitals.

The name staphyloccus is derived from the Greek (staphyle, a bunch of grapes). The designation describes the typical grape-like clustered arrangement of staphylococci viewed under a light microscope. Staphylococci are divided into two groups based on the presence or absence of the plasma-clotting enzyme called coagulase. The coagulase-positive staphylococci consist mainly of Staphylococcus aureus and the coagulase-negative group consists primarily of Staphylococcus epidermidis and Staphylococcus saprophyticus. Because the treatment of infections caused by these bacteria can be different, the coagulase test provides a rapid means of indicating the identity of the bacteria of concern.

Staphylococci are not capable of movement and do not form spores. They are capable...