Staphylococcus is a genus of gram-positive bacterium (see GRAM’S STAIN; BACTERIA) which under the microscope appears in small masses like bunches of grapes. It is one of the most common infectious micro-organisms and is found, for example, in the PUS discharged from BOILS (FURUNCULOSIS). (See also MICROBIOLOGY.)
n. a genus of Gram-positive nonmotile spherical bacteria occurring in grapelike clusters. Some species are saprophytes; others parasites. Many species produce *exotoxins. The species S. aureus is commonly present on skin and mucous membranes; it causes boils and internal abscesses. More serious infections caused by staphylococci include pneumonia, bacteraemia, osteomyelitis, and enterocolitis. See also MRSA. —staphylococcal adj.
Most staphylococci (see STAPHYLOCOCCUS) have now evolved resistance to benzylpenicillin (see PENICILLIN) because of their ability to produce PENICILLINASE. Cloxacillin and ?ucloxacillin are antibiotics still e?ective against most staphylococci; at one time methicillin was used to combat resistant strains, but in hospital environments bacteria acquired immunity to this powerful drug (now withdrawn from use) and to cloxacillin. RIFAMPICIN, VANCOMYCIN, TEICOPLANIN and temocillin are still active against most penicillinase-producing gram-negative bacteria (see GRAM’S STAIN). There is, however, a growing threat to health because of the rise in the number of antibiotic-resistant bacteria, particularly in hospitals. The bacteria themselves are not more virulent than others, but the di?culty in treating them with a safe and e?ective antibiotic mean that they are more dangerous. It is likely that lapses in normal hygienic practice – such as frequent hand-washing – has resulted in an increase in MRSA disease.... methicillin-resistant staphylococcus aureus (mrsa)
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