CONCISE COMMUNICATION BJD British Journal of Dermatology Biomarkers of Th2 polarity are predictive of staphylococcal colonization in subjects with atopic dermatitis J.A. Warner,* L.Y. McGirt* and L.A. Beck*  *Department of Dermatology, Johns Hopkins Medical Institution, Baltimore, MD 21224, U.S.A.  Department of Dermatology, 601 Elmwood Ave., Box 697, University of Rochester Medical Center, Rochester, NY 14642, U.S.A. Correspondence Lisa A. Beck. E-mail: Lisa_Beck@URMC.Rochester.edu Accepted for publication 19 August 2008 Key words atopic dermatitis, eosinophils, IgE, Staphylococcus aureus Conflicts of interest None declared. DOI 10.1111/j.1365-2133.2008.08905.x Summary Background Staphylococcal colonization of the skin is commonly observed in sub- jects with atopic dermatitis (AD) and correlates with disease severity. Little is known about whether the degree of T-helper 2 (Th2) polarity in these subjects can also affect the frequency of bacterial colonization in this disease. Objectives To determine if there is a correlation between markers of Th2 polarity [serum total IgE, eosinophilia and presence of another atopic disease (allergic rhinitis)] and skin colonization with Staphylococcus aureus in subjects with AD. Methods A retrospective chart review was performed of an academic dermatology clinic focused on the treatment of AD with a single provider. Results Staphylococcus aureus colonization was more commonly observed in subjects with AD who had peripheral eosinophilia, elevated serum IgE levels, and ⁄ or a history of or active allergic rhinitis. Conclusions Results suggest that Th2 polarity may enhance subjects’ risk for bacte- rial colonization. Cutaneous colonization with Staphyloccocus aureus is a common feature of atopic dermatitis (AD), present on the lesional skin of 80–100% of subjects with AD compared with 5–30% of healthy controls. 1 Staphylococcus aureus colonization has been shown to correlate with AD severity as assessed by the subjec- tive scoring system, SCORAD (SCORing Atopic Dermatitis). 2 Some 30–60% of S. aureus strains isolated from patients with AD are able to produce exotoxins with superantigenic proper- ties, such as staphylococcal enterotoxins A, B, C and D and toxic shock syndrome toxin-1. IgE antibodies to these toxins have also been shown to correlate with disease severity. 3 Sub- jects with severe AD are thought to be more susceptible to S. aureus colonization and infection because they have both innate immune defects (e.g. dysfunctional epithelial barrier, reduced production of antimicrobial peptides, and defects in toll-like receptor signalling) and adaptive defects (e.g. T-helper 2 (Th2) polarity). 4–6 We have recently shown that Th2 cytokines can further exacerbate barrier function by reducing filaggrin expression from keratinocytes. 4 This is in line with the evi- dence that interleukin (IL)-4 and IL-13 inhibit the release of antimicrobial peptides from keratinocytes, suggesting that adaptive immune responses can adversely affect innate immune responses. 5,7 To investigate whether biomarkers of Th2 polarity, namely total IgE and peripheral eosinophilia, are predictive of S. aureus colonization, we performed a retrospective study of subjects with AD seen in two university-based dermatology clinics. Previous studies have suggested that these biomarkers of Th2 polarity and the presence of other atopic diseases such as aller- gic rhinitis (AR) are also predictive of AD severity. 2,8,9 With this in mind, we postulated that if elevated biomarkers of atopy, comorbid AR and S. aureus colonization are all associated with more severe AD, then perhaps a direct correlation exists between S. aureus colonization and biomarkers of Th2 polarity and ⁄ or AR. Such a relationship would provide further support that the cutaneous colonization characteristic of AD is second- ary to the adaptive immune response to allergens, namely Th2 cytokines. Materials and methods We performed a retrospective chart review of subjects with AD seen at Johns Hopkins Bayview Medical Center Dermatol- ogy Clinic from July 2001 to April 2006, and at University of Rochester Medical Center Dermatology Clinic from October 2006 to March 2007. We identified 257 subjects with AD diagnosed by a single provider (L.A.B.) based on the Pediatric Consensus guidelines. 10 Data on age, sex and history of AR were collected on all subjects. Serum total IgE levels, total eosinophil counts and bacterial cultures were obtained on a subset of these subjects. The following were considered to be threshold levels indicative of significant Th2 polarity: serum total IgE ‡ 100 kU L )1 and total eosinophil count ‡ 300 cells mm )3 . Ó 2008 The Authors Journal Compilation Ó 2008 British Association of Dermatologists • British Journal of Dermatology 2009 160, pp183–185 183