Exploring Staphylococcus epidermidis in atopic eczema: friend or foe?

BACKGROUND: Staphylococcus aureus (SA) colonization/infection is important in the pathophysiology of childhood atopic dermatitis (AD), but the role of Staphylococcus epidermidis (SE) is unknown.

AIM: To evaluate if SE co-infects with SA and is associated with more severe disease.

METHODS: Associations between bacteriological culture results of skin swabs (taken from the most severely affected area and at the antecubital fossa) and SCORing Atopic Dermatitis (SCORAD) score, skin hydration, transepidermal water loss (TEWL) and quality of life (QoL) were evaluated.

RESULTS: In 100 consecutive patients with AD (aged 12.4 ± 4.8 years), SE was present in 28% and 32% of the swabs taken from the most severe area and the flexural area (antecubital fossa), respectively, whereas SA was present in 69% and 55%, respectively. Binomial logistic regression showed that SE was inversely associated with SA growth in the most severely affected skin site [adjusted odds ratio (aOR) = 0.42, 95% CI 0.22-0.81; P = 0.01], frequency of emollient usage (aOR = 0.50, 95% CI 0.29-0.87; P = 0.01) and frequency of oral antihistamine usage (aOR = 0.81, 95% CI 0.65-0.10, P < 0.05), but positively associated with objective SCORAD (aOR = 1.04, 95% CI 1.00-1.02; P < 0.05). SE in the antecubital fossa was not associated with SA growth, disease severity, QoL or any clinical parameters.

CONCLUSIONS: SE may not be just a commensal bystander in the skin microbiota. The organism amensalistically displaces SA and is associated with more severe disease.