Superantigens and adhesins of infant gut commensal Staphylococcus aureus strains and association with subsequent development of atopic eczema

Summary Background According to the hygiene hypothesis, insufficient immune activation by microbes increases the risk of allergy development. Staphylococcus aureus, which is part of the skin and gut microbiota of infants in Western countries, produces a variety of T‐cell‐activating enterotoxins, called superantigens. Objectives To investigate whether early (0–2 months of age) gut colonization by S. aureus strains that carry specific superantigens and adhesins was related to subsequent development of atopic eczema in a Swedish birth cohort. Methods Staphylococcus aureus was isolated from rectal swabs and cultured quantitatively from faecal samples, with individual strains being tested for carriage of genes for superantigens and adhesins. Atopic eczema was diagnosed at onset of symptoms and at 18 months of age. Results Although the frequency of early gut colonization by S. aureus was not related to subsequent eczema development, the S. aureus strains that were found to colonize those infants who developed atopic eczema were less likely to carry the gene encoding the superantigen SElM (P = 0·008) and the gene for elastin‐binding protein (P = 0·03), compared with strains that were isolated from infants who had not developed atopic eczema by 18 months of age. Conclusions Gut colonization by S. aureus strains carrying a certain combination of superantigen and adhesin genes was negatively associated with subsequent development of atopic eczema. Such strains may provide stimulation and promote maturation of the infant immune system. What's already known about this topic? Insufficient immune activation by microbes increases the risk of allergy development. Staphylococcus aureus produces a variety of T‐cell‐activating enterotoxins, called superantigens. The association of superantigens with development of atopic eczema has not previously been investigated. What does this study add? The superantigen genes selm and seln were significantly more prevalent in S. aureus strains that colonized the guts of infants who remained noneczematous for 18 months than in strains that colonized infants who subsequently developed atopic eczema. We found no significant negative association between S. aureus colonization and later development of eczema. The putative protective effect of S. aureus strains appears to be linked to a specific combination of superantigens and adhesins. Linked Comment: Lindberg and Söderquist. Br J Dermatol 2017; 176:297–298.