Background and Objectives: As one of the major skin fatty acids, cis-6-hexadecenoic acid (C16:1Δ6) exhibits a specific antibacterial activity and might play a specific role in the defense mechanism against Staphylococcus aureus, in healthy subjects whereas S. aureus frequently colonizes the skin of patients with atopic dermatitis (AD). Methods: Fatty acid composition of sebum at the recovery level was analyzed by gas chromatography and S. aureus colonizing the skin was assessed by the ‘cup-scrub’ method (9 patients and 10 healthy controls). To evaluate in vivo effect of C16:1Δ6 on colonization, C16:1Δ6 was applied for 2 weeks on the upper arm skin of another group of AD patients (11 patients). Results: Analysis of sebum lipids revealed that there is a significant lower free C16:1Δ6 content in nonlesional skin from AD patients compared with healthy controls. This lower content is also accompanied by a significantly lower level of C16:1Δ6 in the total fatty acid composition of sebum (analyzed following hydrolysis). The lower level of free C16:1Δ6 correlated significantly (R2 = 0.41, p < 0.01) with the numbers of S. aureus colonizing nonlesional skin. Topical application of free C16:1Δ6 on the skin of AD patients for 2 weeks abolished the markedly increased bacterial count in 6 out of the 8 AD patients tested. Conclusions: Free C16:1Δ6 may be involved in the defense mechanism against S. aureus in healthy skin and this deficit triggers the susceptibility of the skin to colonization by S. aureus in AD.

Keywords:
Atopic dermatitis, cis-6-Hexadecenoic acid, Skin surface lipids, Staphylococcus aureus, Antibacterial activity
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© 2005 S. Karger AG, Basel
2005
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