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Microbes shared between healthy caregivers and children with atopic dermatitis

Published: March 19, 2022

Atopic dermatitis (AD) is a highly prevalent, chronic skin condition affecting 15-20% of children worldwide. Patients with moderate to severe disease suffer from complications such as frequent flares, superimposed bacterial and viral skin infections as well as significantly impaired quality of life from intense itching and sleep deprivation. Due to observations showing enrichment of Staphylococcus aureus during flares, clinical management includes eradicating this bacterium from the skin. However, current interventions are generally ineffective in preventing disease relapse and re-colonization with S. aureus upon treatment cessation is common, which could contribute to recurring disease. A possible source for S. aureus re-acquisition are the skin surfaces of clinically healthy caregivers of paediatric AD patients. Determining the extent of skin microbial sharing between paediatric AD patients and their caregivers is thus pertinent for evaluating if these healthy adult caregivers should also be included in strategies for long term management of AD.

In a recent study published in The Journal of Allergy and Clinical Immunology (JACI), Chia et al studied shared signatures in the skin microbial communities of children with AD and their healthy caregivers. The investigators recruited a cohort of children with AD and their healthy caregivers (n = 30 families, two from each family), as well as matched pairs from control households (n = 30 families). Skin microbial DNA and S. aureus strains isolated from the skin of participants were sequenced to uncover common bacterial signatures between primary caregiver and child in AD households versus controls.

The results revealed that there were distinctive microbial signatures in the non-lesional skin of AD children and their healthy caregivers. In particular, a higher ratio of S. aureus abundances relative to the commensal Staphylococcus hominis (the A/H ratio) was found to be a sensitive and specific marker for affiliation to an AD household, regardless of whether they were otherwise healthy adults or children (Accuracy > 0.74 and AUC > 0.80). In addition, S. aureus isolates from caregiver-child pairs from the same AD household had genomes which were highly similar (99.998-99.999% average nucleotide identity; 5/6 AD households), and expressed the enterotoxins Q, K2 and K in culture.

Altogether, the data suggest that microbial risk factors for AD, especially identical S. aureus strains, could be transferred by close physical contact in the home, and that healthy caregiver skin may be a reservoir for microbial sharing. These findings provide a basis for larger scale investigations into intra-familial transmission of pathogenic S. aureus strains and the overall skin microbiome community in AD. Evidence of skin microbial sharing between parent and patient further supports the inclusion of healthy caregivers in strategies for treating recurrent paediatric AD.

The Journal of Allergy and Clinical Immunology (JACI) is an official scientific journal of the AAAAI, and is the most-cited journal in the field of allergy and clinical immunology.

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