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Staphylococcus
	SEM micrograph of S. aureus colonies; note the grape-like clustering common to Staphylococcus species.
Scientific classification
Kingdom:	Bacteria;
Phylum:	Firmicutes;
Class:	Bacilli;
Order:	Bacillales;
Family:	Staphylococcaceae;
Genus:	Staphylococcus; Rosenbach 1884
Species
	S. afermentans; S. aureus; S. auricularis; S. capitis; S. caprae; S. cohnii; S. epidermidis; S. felis; S. haemolyticus; S. hominis; S. intermedius; S. lugdunensis; S. pettenkoferi; S. saprophyticus; S. schleiferi; S. simulans; S. vitulus; S. warneri; S. xylosus;

Not to be confused with streptococcus.

Staphylococcus (from the Greek: σταφυλή, staphylē, "bunch of grapes" and κόκκος, kókkos, "granule") is a genus of Gram-positive bacteria. Under the microscope they appear round (cocci), and form in grape-like clusters.^[1]

The Staphylococcus genus include just thirty-three species.^[2] Most are harmless and reside normally on the skin and mucous membranes of humans and other organisms. Found worldwide, they are a small component of soil microbial flora.^[3]

[edit] Role in disease

Main article: Staphylococcal infection

Staphylococcus can cause a wide variety of diseases in humans and other animals through either toxin production or invasion. Staphylococcal toxins are a common cause of food poisoning, as it can grow in improperly-stored food.

[edit] Classification

The main classification of staphylococci is based on their ability to produce coagulase, an enzyme that causes blood clot formation..

[edit] Coagulase-positive

S. aureus is coagulase-positive, meaning that they can produce coagulase. However, while the majority of S. aureus are coagulase-positive, some may be atypical in that they do not produce coagulase. S aureus is also 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 Enterococci and Streptococci.
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.

[edit] Coagulase-negative

S. epidermidis, a coagulase-negative staphylococcus species, is a commensal of the skin, but can cause severe infections in immune-suppressed 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 staphylococcus species are CoNS and CNS.

[edit] Biochemical identification

Staphylococcus species can be differentiated from other aerobic and facultative anaerobic gram positive cocci by several simple tests. Staphylococcus spp. are facultative anaerobes. Facultative anaerobes are capable of growth both aerobically and anaerobically. All species grow in the presence of bile salts and are catalase positive. Growth also occurs in a 6.5% NaCl solution. On Baird Parker Medium Staphylococcus spp. show as fermentative, except for S. saprophyticus which is oxidative. Staphylococcus spp. are resistant to Bacitracin (0.04 U resistance = <10mm zone of inhibition) and susceptible to Furazolidone (100μg resistance = <15mm zone of inhibition).

Further biochemical testing is needed to identify down to the species level.

[edit] Genomics and molecular biology

The first S. aureus genomes to be sequenced were those of N315 and Mu50 in 2001. Many more complete S. aureus genomes have been submitted to the public databases, making S. aureus one of the most extensively sequenced bacteria. The use of genomic data is now widespread and provides a valuable resource for researchers working with S. aureus. Whole genome technologies such as sequencing projects and microarrays have shown there is an enormous variety of S. aureus strains. Each contains different combinations of surface proteins and different toxins. Relating this information to pathogenic behaviour is one of the major areas of staphylococcal research. The development of molecular typing methods has enabled the tracking of different strains of S. aureus. This may lead to better control of outbreak strains. A greater understanding of how the staphylococci evolve, especially due to the acquisition of mobile genetic elements encoding resistance and virulence genes is helping to identify new outbreak strains and may even prevent their emergence.^[4]

[edit] See also

^ Ryan KJ, Ray CG (editors) (2004). Sherris Medical Microbiology (4th ed.). McGraw Hill. ISBN 0838585299.
^ Holt JG (editor) (1994). Bergey's Manual of Determinative Bacteriology (9th ed.). Williams & Wilkins. ISBN 0-683-00603-7.
^ Madigan M, Martinko J (editors). (2005). Brock Biology of Microorganisms (11th ed.). Prentice Hall. ISBN 0131443291.
^ Lindsay J (editor). (2008). Staphylococcus: Molecular Genetics. Caister Academic Press. ISBN 978-1-904455-29-5 . ISBN 1904455298. http://www.horizonpress.com/staph.

[Sherris-0] Ryan KJ, Ray CG (editors) (2004). Sherris Medical Microbiology (4th ed.). McGraw Hill. ISBN 0838585299.

[Holt_1994-1] Holt JG (editor) (1994). Bergey's Manual of Determinative Bacteriology (9th ed.). Williams & Wilkins. ISBN 0-683-00603-7.

[Brock-2] Madigan M, Martinko J (editors). (2005). Brock Biology of Microorganisms (11th ed.). Prentice Hall. ISBN 0131443291.

[LindsayJ-3] Lindsay J (editor). (2008). Staphylococcus: Molecular Genetics. Caister Academic Press. ISBN 978-1-904455-29-5 . ISBN 1904455298. http://www.horizonpress.com/staph.

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