Conclusion
Numerous studies have now reported that the composition of the skin
microbiome is closely associated with AD flares, severity, and response
to various treatment modalities. However, skin microbiota is not the
sole factor in AD where genetics, immunology and environmental
influences also play important roles.
Several gaps in the existing literature remain to be filled and it is
hoped that future studies will address these (Table 1). Many studies
currently demonstrate differences in skin microbiota composition in
cases and controls at a single timepoint, which limits our ability to
make conclusions about causality and temporal progression; or focus on
bacterial species alone but do not explore other microbes such as
viruses and fungi or their interactions with bacteria and the host.
There is also a lack of mechanistic understanding of functional units in
the skin microbiome and whether differences in microbial abundance
impacts clinical disease or are mere bystanders reflecting fluctuations
in clinical disease.
Future research should focus on several broad areas: (1) A mechanistic
understanding of whether skin microbial shifts modulate or merely
reflect AD and FA pathogenesis, treatment response or disease
prevention; (2) Functional analysis of all skin microbes including
bacteria, viruses, fungi and mites in deep metagenomic studies
integrated with culture methods and skin barrier function analysis to
understand their potential interactions with each other to impact
disease phenotypes or progression; (3) Longitudinal studies to identify
the window of opportunity for intervention, if any; (4) Evaluating the
efficacy, sustainability and patient selection for microbe-based
biotherapeutics in disease treatment and prevention. (Table 1).
Several interventional trials that are underway in children with AD
focus mainly on monitoring skin microbiota changes in response to
treatment and microbiota-based interventions, such as probiotics in
topical creams and vaginal microbiota seeding (Table 2). However, apart
from the latter study, the majority of these trials plan only to
document changes in skin microbiota composition as secondary aims. There
is a clear need for more robust studies to fill the gaps described
above, and to move the field away from merely descriptive studies to
understanding the mechanistic role and functions of skin microbiota in
disease pathogenesis and treatment, and to evaluate the potential to
harness them for targeted biotherapeutic interventions or as validated
biomarkers of disease.