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Staphylococcus, from Ancient Greek σταφυλή ( staphulḗ), meaning "bunch of grapes", and κόκκος ( kókkos), meaning "kernel" or "Kermes", is a genus of Gram-positive bacteria in the family Staphylococcaceae from the order Bacillales. Under the microscope, they appear spherical (cocci), and form in grape-like clusters. Staphylococcus species are facultative anaerobic organisms (capable of growth both aerobically and anaerobically).
The name was coined in 1880 by Scottish surgeon and bacteriologist Alexander Ogston (1844–1929), following the pattern established five years earlier with the naming of Streptococcus. It combines the prefix "staphylo-" (from ), and suffixed by the (from ).
Staphylococcus was one of the leading infections in hospitals and many strains of this bacterium have become antibiotic resistant. Despite strong attempts to get rid of them, staphylococcus bacteria stay present in hospitals, where they can infect people who are most at risk of infection.
Staphylococcus includes at least 44 species. Of these, nine have two subspecies, one has three subspecies, and one has four subspecies. Many species cannot cause disease and reside normally on the skin and of humans and other animals. Staphylococcus species have been found to be Nectar microbes. They are also a small component of the soil biology. (2025). 9780131443297, Prentice Hall. ISBN 9780131443297
A twelfth group – that of S. caseolyticus – has now been removed to a new genus, Macrococcus, the species of which are currently the closest known relatives of Staphylococcus.
Two species were described in 2015 – Staphylococcus argenteus and Staphylococcus schweitzeri – both of which were previously considered variants of S. aureus.
A new coagulase negative species – Staphylococcus edaphicus – has been isolated from Antarctica. This species is probably a member of the S. saprophyticus group.
Group A includes S. aureus, S. borealis, S. capitis, S. epidermidis, S. haemolyticus, S. hominis, S. lugdunensis, S. pettenkoferi, S. simiae and S. warneri.
Group B includes S. arlettae, S. cohnii, S. equorum, S. saprophyticus and S. xylosus.
Group C includes S. delphini, S. intermedius and S. pseudintermedius.
Members of the S. sciuri group are oxidase-positive due to their possession of the enzyme cytochrome c oxidase. This group is the only clade within the staphylococci to possess this gene.
The S. sciuri group appears to be the closest relations to the genus Macrococcus.
S. pulvereri has been shown to be a junior synonym of S. vitulinus.
Within these clades, the S. haemolyticus and S. simulans groups appear to be related, as do the S. aureus and S. epidermidis groups.
S. lugdunensis appears to be related to the S. haemolyticus group.
S. petrasii may be related to S. haemolyticus, but this needs to be confirmed.
The taxonomic position of S. lyticans, S. petrasii, and S. pseudolugdunensis has yet to be clarified. The published descriptions of these species do not appear to have been validly published.
Staphylococcus species can be differentiated from other aerobic and facultative anaerobic, Gram-positive cocci by several simple tests. Staphylococcus species are facultative anaerobes (capable of growth both aerobically and anaerobically). All species grow in the presence of bile salts.
All strains of Staphylococcus aureus were once thought to be coagulase-positive, but this has since been disproven. (2025). 9780838585290, McGraw Hill. ISBN 9780838585290PreTest, Surgery, 12th ed., p. 88
Growth can also occur in a 6.5% NaCl solution. On Baird-Parker medium, Staphylococcus species grow fermentatively, except for S. saprophyticus, which grows oxidatively. Staphylococcus species are resistant to bacitracin (0.04 U disc: resistance = < 10 mm zone of inhibition) and susceptible to furazolidone (100 μg disc: resistance = < 15 mm zone of inhibition). Further biochemical testing is needed to identify to the species level.
Seven species are currently recognised as being coagulase-positive: S. aureus, S. delphini, S. hyicus, S. intermedius, S. lutrae, S. pseudintermedius, and S. schleiferi subsp. coagulans. These species belong to two separate groups – the S. aureus ( S. aureus alone) group and the S. hyicus-intermedius group (the remaining five).
S. aureus is coagulase-positive, meaning it produces coagulase. However, while the majority of S. aureus strains are coagulase-positive, some may be atypical in that they do not produce coagulase. S. aureus is catalase-positive (meaning that it can produce the enzyme catalase) and able to convert hydrogen peroxide (H2O2) to water and oxygen, which makes the catalase test useful to distinguish staphylococci from Enterococcus and Streptococcus.
S. pseudintermedius inhabits and sometimes infects the skin of domestic dogs and cats. This organism, too, can carry the genetic material that imparts multiple bacterial resistance. It is rarely implicated in infections in humans, as a zoonosis.
S. epidermidis, a coagulase-negative species, is a commensal of the skin, but can cause severe infections in immunosuppressed patients and those with central venous catheters. S. saprophyticus, another coagulase-negative species that is part of the normal vaginal flora, is predominantly implicated in genitourinary tract infections in sexually active young women. In recent years, several other Staphylococcus species have been implicated in human infections, notably S. lugdunensis, S. schleiferi, and S. caprae.
Common abbreviations for coagulase-negative staphylococci are CoNS, CNS, or CNST. The American Society for Microbiology abbreviates coagulase-negative staphylococci as "CoNS".
The widespread incidence of antibiotic resistance across various strains of S. aureus, or across different species of Staphylococcus has been attributed to horizontal gene transfer of genes encoding antibiotic/metal resistance and virulence. A recent study demonstrated the extent of horizontal gene transfer among Staphylococcus to be much greater than previously expected, and encompasses genes with functions beyond antibiotic resistance and virulence, and beyond genes residing within the mobile genetic elements.
Various strains of Staphylococcus are available from biological research centres, such as the National Collection of Type Cultures.
Staphylococcus aureus has emerged as a leading agent of sepsis. It facilitates factors such as tissue adhesion, immune evasion, and host cell injury. In the bloodstream, these factors cause inflammation, impair immune cell function, alter coagulation, and compromise vascular integrity. When left untreated, S. aureus triggers pathophysiologic disturbances that are further amplified by the host inflammatory response, culminating in the severe clinical manifestations of sepsis and septic shock.
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