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31-12-2009 | Dermatology | Article

Bacterial lipoprotein implicated in infected AD


Free abstract

MedWire News: A lipoprotein produced by the bacterium Staphylococcus aureus may be involved in increased skin inflammation associated with infected atopic dermatitis (AD), research suggests.

The Staphylococcal cell wall lipoprotein lipoteichoic acid (LTA) was identified at sufficient levels to induce inflammatory cytokine gene expression in epidermal cells, the researchers report.

They also found that the LTA amounts correlated with eczema area and severity, which the researchers say suggests “that LTA may be an important component of the ability of S. aureus to exacerbate AD lesions.”

S. aureus infection is a known trigger for the worsening of AD but the exact mechanisms behind this are unknown, say Jeffrey Travers and colleagues from the Indiana University School of Medicine in Indianapolis.

To investigate further, they studied wash fluid from clinically impetiginized AD lesions in 89 children that had been graded according to the Eczema Area and Severity Index (EASI).

Participants were then treated with a regimen that included topical corticosteroids and systemic antibiotics, and the lesion was reanalyzed after 2 weeks.

S. aureus was identified in 79 of the children, and the bacterial colony-forming unit (CFU) correlated significantly with the EASI lesional score.

LTA levels as high as 9.8 μg/ml were identified in wash fluid samples, and these concentrations correlated with the lesional EASI scores and S. aureus CFU.

Approximately 30% of clinically impetiginized AD lesions contained levels of LTA greater than 1 mg/ml, and injection of skin tissue ex vivo with the LTA quantities found in AD lesions resulted in epidermal cytokine gene expression.

The researchers note in the Journal of Allergy and Clinical Immunology that participants harboring methicillin-resistant S. aureus (MRSA) also had greater total body clinical dermatitis scores than those free of the bacteria.

“These findings could have clinical importance, and the presence of widespread impetiginized AD should alert the clinician to consider the possibility of infection with MRSA,” they say.

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By Anita Wilkinson