Veterinary bacteriology: information about important bacteria
|Species/Subspecies:||Staphylococcus aureus subsp. aureus|
|Categories:||Zoonotic; causes hemolysis|
|Etymology:||Genus name: bunch of grape-like cocci (coccus means a grain or berry)|
Species epithet: golden
Subspecies epithet: see Species epithet
|Type Strain:||ATCC 12600 och 12600-U = CCUG 1800 = NCTC 8532.|
Medium (2-3 mm in diameter) sized, opaque, white or yellow colonies. Low convex and with smooth edges. They often give a double hemolysis zone on blood agar [a clear (complete) narrow inner zone, and a turbid (partial) broad outer zone].
The complete hemolysis of Staphylococcus spp. is caused by an α-hemolysin and the partial hemolysis by a β-hemolysin. Cf. Streptococcus spp.
|Micromorphology:||Non-motile cocci in clusters.|
|Gram +/Gram -:||G+|
|Other Enzymes:||Coagulase + (most strains), esculinase -, urease +.|
|Biochemical Tests:||Voges-Proskauer +|
|Fermentation of carbohydrates:
Other carbohydrates: mannose +.
|Spec. Char.:||S. aureus produces a polysaccharide kapsel.|
Baird-Parker agar is used for bacteriological analysis of food samples.
SELMA- or SELMA Plus plates are used for cultivation of milk samples when mastitis is suspected.
For cultivation of Methicillin Resistant Staphylococcus aureus (MRSA), selective media such as chromogenic media could be used.
|Virulence Factors:||α-toxin (hemolysin) is a porin that causes cell death of sensitive cells, i.e. those cells that possess the receptor for α-toxin (platelets and monocytes).
β-toxin (hemolysin) is a sphingomyelinase (phospholipase).
γ-toxin (hemolysin) is also a porin, which can lyse sensitive cells.
δ-toxin (hemolysin) is a peptide composed of 26 amino acids, which acts as a biodetergent and can lyse many different types of cells.
Protein A is an outer membrane protein that binds to the Fc region of IgG molecules. Thus, the Fab regions will be exposed on the surface of the bacterium and that will prevent opsonization and phagocytosis.
Coagulase is an extracellular protein that binds to prothrombin and forms a complex (staphylothrombin), where the protease activity of thrombin will be initiated, so that fibrinogen is converted to fibrin. There is no conclusive evidence that coagulase is a virulence factor, but it is believed that the bacteria are protected against phagocytosis by causing local clots.
|16S rRNA Seq.:|
||About 70 species and subspecies have been described within the genus Staphylococcus. S. aureus subsp. aureus is as the name implies closely related to S. aureus subsp. anaerobius.|
|Comment:||Streptococcus pyogenes is also causing impetigo in humans.|
|Reference(s):||No. 16, 42, 50|