Staphylococcus

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{{Taxobox | color = lightgrey | name = Staphylococcus | regnum = Bacteria | phylum = Firmicutes | classis = Bacilli | ordo = Bacillales | familia = Staphylococcaceae | genus = Staphylococcus | genus_authority = Rosenbach 1884 | subdivision_ranks = Species | subdivision = S. aureus
S. auricularis
S. capitis
S. caprae
S. epidermidis
S. haemolyticus
S. hominis
S. lugdunensis
S. saprophyticus
S. schleiferi
S. warneri
S. xylosus }} Staphylococcus (in Greek staphyle means bunch of grapes and coccos means granule) is a genus of gram-positive bacteria. Under the microscope they appear round (cocci), and form in grape-like clusters.

There are about thirty species of staphylococci. Most are completely harmless, and reside normally on the skin and mucous membranes of humans and other organisms. They are a small component of soil microbial flora. This genus is found world wide.

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Role in disease

Staphylococci can cause a wide variety of diseases in humans either through toxin production or invasion. Staphylococcal toxins are an uncommon cause of food poisoning but are not affected by cooking. The bacteria grow in improperly stored food. Although the cooking process kills them, the enterotoxins are heat resistant. Staphylococci can grow in foods with relatively low water activity (such as cheese and salami).

One pathogenic species is Staphylococcus aureus, which can infect wounds. These bacteria can survive on dry surfaces, increasing the chance of transmission. Of this type, Methicillin-resistant Staphylococcus aureus (MRSA) has recently become a major cause of hospital-acquired infections and is being recognized with increasing frequency in community acquired infections. S. aureus is also implicated in toxic shock syndrome; during the 1980s some tampons allowed the rapid growth of S. aureus, which released toxins that were absorbed into the bloodstream. Any S. aureus infection can cause the staphylococcal scalded skin syndrome, a cutaneous reaction to exotoxin absorbed into the bloodstream. It can also cause a type of septicaemia called pyaemia.

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, 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.

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