Staphylococcus aureus

Staphylococcus aureus is a Gram-positive round-shaped bacterium, a member of the Firmicutes, and is a usual member of the microbiota of the body, frequently found in the upper respiratory tract and on the skin. It is often positive for catalase and nitrate reduction and is a facultative anaerobe that can grow without the need for oxygen.[1] Although S. aureus usually acts as a commensal of the human microbiota it can also become an opportunistic pathogen, being a common cause of skin infections including abscesses, respiratory infections such as sinusitis, and food poisoning. Pathogenic strains often promote infections by producing virulence factors such as potent protein toxins, and the expression of a cell-surface protein that binds and inactivates antibodies. The emergence of antibiotic-resistant strains of S. aureus such as methicillin-resistant S. aureus (MRSA) is a worldwide problem in clinical medicine. Despite much research and development, no vaccine for S. aureus has been approved.

Staphylococcus aureus
Scanning electron micrograph of S. aureus; false color added
Scientific classification
Domain: Bacteria
Phylum: "Firmicutes"
Class: Bacilli
Order: Bacillales
Family: Staphylococcaceae
Genus: Staphylococcus
S. aureus
Binomial name
Staphylococcus aureus
Staphylococcus aureus
Other namesStaph aureus, S. aureus
SpecialtyInfectious disease
TypesMethicillin-Susceptible Staphylococcus Aureus, Methicillin-resistant Staphylococcus aureus
CausesStaphylococcus aureus bacteria
Differential diagnosisother bacterial, viral and fungal infections,
Preventionhand washing, cleaning surfaces
Frequency20% to 30% of the human population often without symptoms
Staphylococcus aureus on basic cultivation media
Hemolysis on blood agar, DNase activity, clumping factor, latex agglutination, growth on mannitol-salt and Baird-Parker agar, hyaluronidase production.

An estimated 20% to 30% of the human population are long-term carriers of S. aureus[2][3] which can be found as part of the normal skin flora, in the nostrils,[2][4] and as a normal inhabitant of the lower reproductive tract of women.[5][6] S. aureus can cause a range of illnesses, from minor skin infections, such as pimples,[7] impetigo, boils, cellulitis, folliculitis, carbuncles, scalded skin syndrome, and abscesses, to life-threatening diseases such as pneumonia, meningitis, osteomyelitis, endocarditis, toxic shock syndrome, bacteremia, and sepsis. It is still one of the five most common causes of hospital-acquired infections and is often the cause of wound infections following surgery. Each year, around 500,000 patients in hospitals of the United States contract a staphylococcal infection, chiefly by S. aureus.[8] Up to 50,000 deaths each year in the USA are linked with S. aureus infections.[9]

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