How common is S aureus colonization and where does it occur?

Updated: Sep 24, 2019
  • Author: Lisa S Lewis, MD; Chief Editor: Russell W Steele, MD  more...
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Answer

Approximately 30% of the population is colonized in the anterior nares by S aureus. Some individuals colonized by S aureus experience recurrent episodes of impetigo on the nose and lip. Bacteria can spread from the nose to healthy skin within 7-14 days, with impetigo lesions appearing 7-14 days later.

Approximately 10% of individuals are colonized with S aureus in the perineum and, more uncommonly, in the axillae, pharynx, and hands. Individuals who are permanent carriers serve as reservoirs of the infection for other people. Most healthy persons transiently harbor S aureus as part of their microbial flora. S aureus often passes from one individual to another through direct hand contact, entering through broken skin created by cutaneous diseases.

Patients with atopic dermatitis or other inflammatory skin conditions more commonly have skin colonized by S aureus. Studies have shown a 60-90% S aureus colonization rate in patients with atopic dermatitis. Patients with atopic dermatitis, particularly those with a history of eczema herpeticum, are at higher risk of developing an infection caused by MRSA.

One study found significantly lower expression of proteins related to the skin barrier and generation of natural moisturizing factor in lesional versus nonlesional sites in patients with atopic dermatitis. In addition, epidermal fatty acid–binding protein was expressed at significantly higher levels in patients colonized with MRSA, and this might perpetuate the inflammatory response through eicosanoid signaling. [8]


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