Influence of narrow-band UVB phototherapy on cutaneous microbiota of children with atopic dermatitis

Abstract

Objective: In the present work, the effect of narrow-band ultraviolet B (UVB) phototherapy on a cutaneous microbial population was evaluated in patients with atopic dermatitis (AD) and compared with control patients (vitiligo).

Methods: Count, isolation and identification of cutaneous microbiota from anticubital fossa were performed in 10 controls and 10 AD patients, both submitted to similar levels (P > 0.05) of UVB phototherapy (4.3 +/- 0.9 and 4.3 +/- 0.8 accumulated joules, respectively). Additionally, Staphylococcus aureus isolates were screened for the production of exotoxins.

Results: The total and staphylococcal cutaneous microbial population levels were higher (P < 0.05) in AD patients than in the controls. All these population levels decreased (P < 0.05) for both AD and control patients after UVB phototherapy, which also decreased the SCORAD for AD patients. All patients with AD and 50% of controls were carriers of S. aureus, and harboured the bacteria simultaneously on skin and anterior nares. All of the S. aureus strains recovered from AD patient skin produced toxin and the B type was the most frequently detected (70%), followed by C (20%) and A (10%) toxins. Only 40% of the S. aureus isolates from control patients produced toxin. After UVB treatment, microbial population levels of AD patients were similar (P > 0.05) to the ones found in control patients before phototherapy, and toxin production ability of S. aureus isolates decreased drastically.

Conclusion: The results of the present study show the beneficial effect of UVB phototherapy on AD and suggest that this may be attributable not only to reduction of skin surface bacteria but also to the suppression of superantigen production from S. aureus.