Microbiology

Staphylococcus aureus

Staphylococcus aureus

Also known as: S. aureus, Staph, Methicillin-susceptible Staphylococcus aureus (MSSA)

Industry of Interest: Healthcare

Classification: Bacteria

Microbiology: Staphylococcus aureus is a Gram-positive coccus that forms “grape-like” clusters of cells. It is also known for the “golden” appearance of its colonies, which is produced by a protective carotenoid pigment called Staphyloxanthin (Clanditz et al., 2006). S. aureus is an opportunistic pathogen with many toxins and virulence factors at its disposal.

 

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Biology

Habitat and transmission: S. aureus is a commensal microorganism that colonises around 20% of humans constantly and around 60% of individuals intermittently throughout their lives (Klutymans et al., 1997). S. aureus frequently resides on the skin and mucosal surfaces and is most commonly found in areas of the body such as the nasopharynx, axillae and perineum. The microorganism can be transferred by person-to-person contact or via the environment because S. aureus has been known to survive for up to 7 months on dry surfaces (Kramer et al., 2006). Generally S. aureus resides on humans with little consequence. However, if mucosal barriers or the skin have been compromised or the person is immunosuppressed in some way then infections can readily occur.

Treatment and antibiotic resistance: Generally S. aureus infections can be treated effectively using b-lactam antibiotics. However, some S. aureus strains have developed resistance to antibiotics such as penicillin and methicillin. These strains are commonly associated with nosocomial infection and are increasingly difficult to treat with currently available antibiotics.

Prevention and control: MSSA strains do not have specifically outlined prevention and control measures like MRSA strains. However, improvement of patient and staff hand hygiene and thorough environmental decontamination, particularly of frequently touched sites, reduces the likelihood transmission of S. aureus.

Symptoms/Effects

Disease and symptoms: S. aureus is known to cause superficial skin infections such as boils, abscesses, acne and cellulitis. However, S. aureus can produce a wide variety of extracellular and surface virulence factors that can cause more serious disease such as endocarditis, septicaemia, toxic shock syndrome and meningitis, which can be life-threatening.

Technical

References:

Brosnahan A. and Schlievert P.M. (2011) Gram-positive bacterial superantigen outside-in signalling causes toxic shock syndrome. FEBS J. [E Pub Ahead of Print] doi: 10.1111/J.1742-4658.2011.08151.x

Clanditz A., Resch A., Wieland K.P., Peschel A., Gotz F. (2006) Staphyloxanthin plays a role in the fitness of Staphylococcus aureus and its ability to cope with oxidative stress. Infection and Immunity. 74(8): 4950-4953.

 

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