Background Eczema is a common skin inflammatory disorder during infancy. An increasing number of studies have shown an association between eczema and skin microbiome fluctuations. Skin dysbiosis was reported to precede the onset of infant eczema by both culture-based and sequencing-based analyses. However, the pathophysiology of eczema is highly complex and heterogenous. Given that eczema is an umbrella term for atopic (IgE-associated) and non-atopic (non-IgE-associated) forms of eczema, whether skin microbiome plays an important role in determining the subtypes of eczema by atopic status still remains unclear.
Objectives This prospective study aimed to investigate whether profile of early-life skin microbiome in atopic eczema patients was different from that of non-atopic eczema patients.
Methods We followed up 120 Chinese infants in Hong Kong from childbirth for one year. At 12 months, eczema was diagnosed by paediatricians according to Hanifin and Rajka criteria, and meanwhile skin prick test (SPT) for common inhalant and food allergens was conducted to assess atopic status. Based on diagnoses and SPT results, the 120 subjects were further subclassified into atopic eczema group, non-atopic eczema group, and no-active eczema group at 12 months. For each subject, microbes in skin swabs collected at left antecubital fossa were longitudinally sampled at 1, 6 and 12 months. Skin microbiome data was generated by 16S rRNA sequencing. Differentially abundant taxa between atopic and non-atopic eczema groups were assessed by a newly developed statistical methodology called Analysis of Compositions of Microbiomes with Bias Correction (ANCOM-BC).
Results Nighty-seven subjects completed this study, and 33 (34%) had active physician-diagnosed eczema at 12 months. Twenty-six out of 81 (32%) subjects showed positive in SPT. Eighteen was classified as atopic eczema patients, while 12 were classified as non-atopic eczema patients. During the study period in total 297 skin swab samples were collected. Alpha diversity represented by Shannon (p=0.001) and Simpson (p=0.004) indices significantly increased from 1 month to 6 months age, and beta diversity (p=0.001) differed across time as well. Relative abundance of Staphylococcus (p<0.001 and 0.04 respectively) and Corynebacterium (p<0.001 and <0.001 respectively) progressively decreased across time (adjusted p-value: 1 month to 6 months vs 6 months to 12 months). Alpha diversity of skin microbiome at 12 months was significantly lower in atopic eczema patients than that in non-atopic eczema patients (Shannon p=0.002, Simpson p=0.001). Alpha diversity at 1 month and 6 months did not show significant differences among groups. Differences regarding beta diversity and taxa abundance were not found between atopic and non-atopic eczema patients across time.
Conclusions Skin microbiome profiles differ slightly between infantile eczema with and without atopy. Alpha diversity of skin microbiota at left antecubital fossa is lower in atopic eczema patients compared with that of non-atopic eczema patients only during flare-ups at 12 months. This study cannot detect such difference at earlier time points.
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