Effect of Staphylococcus aureus on the Keratinocytes in Atopic Dermatitis

Atopic dermatitis (AD) is associated with Staphylococcus aureus skin colonization. S. aureus strains secrete proteins, virulence factors and enterotoxins that may affect immune function and skin integrity. We sought to investigate how specific Staphylococcal species and strains affect epithelial barrier function. Skin swabs from 20 AD patients and healthy controls were collected. Bacterial species were isolated and bacterial toxin gene expression and production were measured using RIDASCREEN set assay. Human keratinocytes cells were cultured with bacterial supernatants. Transepithelial electrical resistance (TEER) and MTT assays were performed to investigate the effect of staphylococcus toxins on epithelial barrier function and viability. Twenty-four staphylococcus strains were identified from patients with AD and food allergies, three of which were unique S. aureus strains. Bacterial supernatant from two of the S. aureus strains (LK1493 and 1505) decreased the viability of human keratinocytes to 64% (p≤0.001) and 65% (p≤0.001) respectively. Three of the S. capitis strains decreased the mean viability of the cells to 25 (p≤0.0005), 38 (p≤0.001), and 51% (p≤0.005) for strains LK1436, LK1532, and LK1519, respectively. The TEER results showed that two S. aureus strains (LK1422 and LK1493) decreased the epithelial barrier integrity by decreasing the TEER measurements by 40% (p≤0.05) and 60% (p≤0.01) respectively. Staphylococcus strains isolated from AD patients with food allergies decreased cell viability of human keratinocytes, most strongly from S.capitis. and S.aureus strains. S.aureus has the strongest effect on decreasing the epithelial barrier integrity, suggesting that Staphyloccocal strains have a differential effect on the skin viability and integrity