Staphylococcus epiermidis is a member of the bacterial genus Staphylococcus, consisting of Gram-positive cocci arranged in clusters. It is catalase-positive and coagulase-negative and occurs frequently on the skin of humans and animals and in mucous membranes. It is a facultative anaerobe that grows by aerobic respiration or by fermentation. It is sensitive to the antibiotic Novobiocin; a feature that distinguishes it from the other common coagulase negative organism S. saprophyticus. Due to contamination, S. epidermidis is probably the most common species found in laboratory tests.