staphylococcus

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staphylococcus (stăf´ələkŏk´əs), any of the pathogenic bacteria, parasitic to humans, that belong to the genus Staphylococcus. The spherical bacterial cells (cocci) typically occur in irregular clusters [Gr. staphyle=bunch of grapes]. The term staphylococcus is also sometimes used loosely for the cluster arrangement itself and, broadly, for any bacteria with such a growth pattern. The pigments produced by staphylococci are the basis of the names given to the various strains—those with colors ranging from orange to yellow are designated S. aureus; white strains are known as S. albus.

Staphylococci cause abscesses, boils, and other infections of the skin, such as impetigo. They can also produce infection in any organ of the body (e.g., staphylococcal pneumonia of the lungs). The most common form of food poisoning is brought on by staphylococcus-contaminated food. The staphylococcus organisms also generate toxins and enzymes that can destroy both red and white blood cells.

Unlike some other types of bacteria, staphylococci are generally partly or wholly resistant to antibiotic action; this raises serious problems in the treatment and control of staphylococcus infections (see drug resistance). The rise of drug-resistant virulent strains of S. aureus, particularly methicillin-resistant S. aureus (MRSA), has led increasing concern in the medical community. Although sick patients with compromised immune systems and children are most susceptible to the strains, which most typically are contracted in hospital, nursing home, and other health-care settings, healthy persons have also been infected. Pharmaceutical companies are working to develop new antibiotics to kill drug-resistant strains of staphylococcus and other bacteria, and a vaccine for S. aureus has been developed.

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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.

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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.

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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.

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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.

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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.