Skin microbe transmission in households of pediatric AD patients
Besides lesional sites of AD, the anterior nares and inguinal creases are common reservoirs of S. aureus . Clinical studies have shown that S. aureus strains can be shared between the reservoirs and distal skin sites, indicating that skin microbes are spread through physical transfer or through the airborne route.51, 52The seeding of S. aureus between reservoirs and other body sites may promote recolonization, disrupting optimal AD control.
There is also growing appreciation for the importance of other non-self reservoirs and skin microbial transmission between individuals in close contact in perpetuating AD. Studies utilizing 16S or whole genome sequencing of skin microbiomes have further demonstrated a general sharing of skin microbes apart from S. aureus between members of the same household.52, 53 In a cross-sectional study of 30 primary caregiver-child pairs (children aged 4- 10 years) in households with pediatric AD and the same number of age matched control pairs, Chia et al demonstrated significant microbiome similarities between the skin of clinically healthy caregivers and the skin of their children.52 A subset of caregivers in households with pediatric AD also exhibited lower relative abundances of some skin commensals like S. hominis and Dermacoccus nishinomiyaensis . Furthermore, the ratio of S. aureus toS. hominis within skin microbiomes was a more sensitive and specific marker for an individual’s (caregiver or child) affiliation to a house with an AD patient than just S. aureus relative abundances alone, underscoring the importance of additional shared microbial influences within families. While cross-sectional cohorts have shed light on possible microbiome sharing between family members, further studies involving prospective cohorts are necessary to establish stronger evidence for the role of intra-familial microbial transmission in the onset, progression, and recurrence of pediatric AD. These studies are important to establish if the risk of recurrent AD is associated with the re-acquisition of microbes including S. aureus after their eradication following initial treatment.
Taken together, the current literature supports further investigations into whether clinically healthy household members should also undergo decolonization to manage recurrent pediatric AD. A clinical trial has shown that both S. aureus decolonization of all household members of children below 18 years of age (median age 3.9 years, range, 1.1–17.1 years) with community-acquired methicillin-resistant S. aureus (MRSA) skin and soft tissue infections (SSTI) or individualized decolonization of only household members with history of SSTI had a modest effect on the risk of study participants developing future SSTI,54 but no trial has been conducted in the context of recurrent pediatric AD to date. The ineffectiveness of these household decolonization strategies could be due to the lack of decontamination of household surfaces and fomites, which are significant reservoirs of S. aureus , or due to potential complexities with re-acquisition of S. aureus from sources outside the household. More comprehensive decolonization regimes will need to be trialled to evaluate the efficacy of expanding treatment beyond the index patient for managing recurrent pediatric AD.