Staphylococcus aureus

Staphylococcus aureus
Scanning electron micrograph of S. aureus; false color added
Scientific classification
Domain:	Bacteria
Phylum:	Bacillota
Class:	Bacilli
Order:	Bacillales
Family:	Staphylococcaceae
Genus:	Staphylococcus
Species:	S. aureus
Binomial name
Staphylococcus aureus Rosenbach 1884

Staphylococcus aureus is a gram-positive spherically shaped bacterium, a member of the Bacillota, 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. S. aureus is one of the leading pathogens for deaths associated with antimicrobial resistance and the emergence of antibiotic-resistant strains, 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.

An estimated 21% 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 microbiota, in the nostrils,^[2][4] and as a normal inhabitant of the lower reproductive tract of females.^[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 hospital patients in the United States contract a staphylococcal infection, chiefly by S. aureus.^[8] Up to 50,000 deaths each year in the U.S. are linked to staphylococcal infection.^[9]