Staphylococcus Strains in Atopic Dermatitis in Children: Toxins Production and Resistance Properties

Staphylococcus spp. skin colonization is involved in the pathogenesis of atopic dermatitis (AD). While coagulase-positive Staphylococcus (S.) aureus strains are known to worsen symptoms, the role of coagulase-negative staphylococci (CoNS) remains controversial. Further research is needed to clarify the pathogenicity of CoNS in AD patients. A study involving 329 children with AD (mean age: 4.89 years) assessed the frequency of staphylococcal colonization on affected skin, along with the toxin-producing properties and antibiotic resistance of isolated strains. Mild AD: Predominantly colonized by CoNS (especially S. epidermidis). Moderate/Severe AD: Showed a significant increase in S. aureus colonization. CoNS (including S. epidermidis) could produce enterotoxins (A, B, C) and toxic shock syndrome toxin-1 (TSST-1), though less frequently than S. aureus strains. In severe AD, toxin-producing CoNS strains (particularly enterotoxin A producers) were more common than non-toxin-producing strains, suggesting a possible aggravation of inflammation via superantigen-mediated mechanism. CoNS exhibited higher resistance rates than S. aureus. Methicillin-resistance S. epidermidis (MRSE): 23.4%. Methicillin-resistance S. aureus (MRSA): 1.27%. This indicates that CoNS in AD may act as a reservoir for antibiotic resistance genes, complicating treatment. CoNS may contribute to AD pathogenesis through toxin production (exacerbating inflammation) and antibiotic resistance (limiting treatment options). Severe AD may involve a synergistic effect between S. aureus and toxin-producing CoNS.