Staphylococcus (family Micrococcaceae) A genus of bacteria in which the spherical, Gram-positive cells occur singly, in pairs, and in irregular clusters. They are non-motile. They are chemo-organotrophic, and capable of growth in the presence or absence of air. They are found mainly in or on the bodies of mammals. Many can be pathogenic, causing a variety of conditions, including boils, abscesses, food poisoning, etc.

staph·y·lo·coc·cus / ˌstaf(ə)lōˈkäkəs/ • n. (pl. staphylococci / -ˈkäkˌsī; -ˌsē/ ) a bacterium of a genus (Staphylococcus) that includes many pathogenic kinds that cause pus formation, esp. in the skin and mucous membranes.DERIVATIVES: staph·y·lo·coc·cal / -ˈkäkəl/ adj.

Staphylococcus A genus of spherical nonmotile Gram-positive bacteria that occur widely as saprotrophs or parasites. The cells occur in grapelike clusters. Many species inhabit the skin and mucous membranes, and some cause disease in humans and animals. S. aureus infection can lead to boils and abscesses in humans; this species also produces toxins that irritate the gastrointestinal tract and result in staphylococcal food poisoning. Certain strains are resistant to antibiotics, and infection with these is very difficult to treat. For example, some strains of methicillin-resistant S. aureus (MRSA) are now resistant to nearly all antibiotics and pose a grave threat to patients.

staphylococcus Spherical bacterium that grows in grape-like clusters and is found on the skin and mucous membranes of human beings and other animals. Pathogenic staphylococci cause a range of local or generalized infections, including pneumonia and septicaemia. They may be destroyed by antibiotics, although some strains have become resistant.

Staphylococcus (staf-i-loh-kok-ŭs) n. a genus of Gram-positive nonmotile spherical bacteria occurring in grapelike clusters. Some species are saprophytes; others parasites. Many species produce exotoxins. More serious infections that are caused by staphylococci include pneumonia, bacteraemia, osteomyelitis, and enterocolitis. S. aureus a species that causes boils and internal abscesses. See also MRSA.
—staphylococcal adj.