Severe Atopic Dermatitis Is Associated With a High Burden of Environmental Staphylococcus aureus
Authors: Pieretti Mariah M. , Sicherer Scott H. 
Published: October 2008

Leung AD, Schiltz AM, Hall CF, Liu AH. Clin Exp Allergy. 2008;38(5):789–793

PURPOSE OF THE STUDY. It has been established that Staphylococcus aureus worsens atopic dermatitis (AD) by a variety of mechanisms. The purpose of this study was to quantify S aureus burden in the homes of participants with AD of varying severity.

STUDY POPULATION. There were 62 volunteers aged 1 to 40 years. Participants were categorized as having mild (n = 18), moderate (n = 14), severe (n = 15), or no (n = 15) AD.

METHODS. Participants completed questionnaires about their asthma, allergies, and home environment. Patients with AD completed a Lung-Browder diagram, documenting the area and intensity of erythema, excoriation, papulation, and lichenification. From these diagrams, AD severity was calculated by using the Eczema Area and Severity Index (EASI). Subjects collected dust samples from their bed, the floor next to their bed, and the home vacuum bag and sent them to the laboratory for analysis. S aureus DNA was extracted, and quantitative reverse-transcription polymerase chain reaction for the femB gene (an S aureus–specific genomic marker) was performed. Data were log-transformed and then analyzed with analysis of variance, student's t test, and Spearman's r.

RESULTS. Bed dust yielded the highest S aureus concentrations. Participants with severe AD had significantly more S aureus DNA (14.67 pg/mg dust) in bed dust than those with moderate (0.41 pg/mg dust; P &lt; .0001), mild (1.42 pg/mg; P = .0051), and no (0.09 pg/mg; P &lt; .0001) AD. The concentration of S aureus DNA in bed dust strongly correlated with EASI scores. Similar patterns were observed for dust from bedroom floors for both DNA concentrations and EASI scores. The quantity of S aureus DNA from the vacuum samples was significantly higher in participants with severe AD versus moderate, mild, and no AD. However, there was no correlation between EASI scores and concentrations of S aureus DNA from vacuum dust samples.

CONCLUSIONS. S aureus is ubiquitous and was detected in dust samples from almost all homes regardless of disease state. However, house dust from participants with severe AD contained the most S aureus DNA. The correlation between S aureus DNA levels and AD severity is driven by proximity to the patient, as shown by the fact that the bed and bedroom floors from the patients with AD yielded the highest levels of S aureus DNA. In the home and especially the bedroom, higher levels of S aureus may contribute to disease severity and persistence in patients with AD.

REVIEWER COMMENTS. This is the first study to examine the environmental burden of S aureus in the homes of patients with AD. This study concludes that patients with severe AD have higher environmental burdens of S aureus. The source of the S aureus may be shed bacteria from the skin of the patient with AD, and if live organisms persist in house dust, then they may be the source of recolonization of patients’ skin. However, to prove whether the relationship between high environmental load of S aureus and severe AD is cause or effect, additional studies need to be performed, including quantification of bacterial load on the patient's skin as correlated with home environmental burden and quantification of live bacteria in house dust.