The widespread use of topical antibiotics enriches for resistance in Staphylococcus aureus isolated from Atopic Dermatitis patients

Carriage rates of Staphylococcus aureus on affected skin in atopic dermatitis (AD) are approximately 70%. Increasing disease severity during flares and overall disease severity correlate with increased burden of S. aureus. Antimicrobial treatments are therefore routinely used in management of AD. In this study we aimed to determine if genotypic and phenotypic antimicrobial resistance profiles differed in S. aureus isolates from children with AD compared with non-atopic, healthy child nasal carriers. We compared S. aureus isolates from children with AD (n=50) to nasal carriage isolates from children without skin disease (n=49). Using whole genome sequencing we generated a phylogenetic framework for the isolates based on variation in the core genome, then compared antimicrobial resistance phenotype and genotypes between disease groups. This analysis revealed that resistance patterns in AD cases differed from controls. Fusidic acid resistance is more prevalent in children with AD, and the genetic basis of resistance in this population also differs compared with healthy controls. We also identified an increased prevalence of genetic determinants linked with antiseptic tolerance in AD cases compared with controls. The results are suggestive of strong selective pressure driving the emergence and maintenance of specific resistances in AD.