CONICET | Buscador de Institutos y Recursos Humanos

Staphylococcus aureus, a colonizer of 30% of the population, is the most common cause of skin and soft tissue infections. The skin is the main target of UV radiation (UVr), which modulates cutaneous immune responses. The increasing incidence of resistant S. aureus (methicillin resistant S. aureus-MRSA), has major implications forcurrent as well as future treatment options for this pathogen. This study was aimed at evaluating the use of UVr as an adjuvant treatment for MRSA skin infection.To select the UVr dose, Balb/c mice were irradiated on their back ith 0, 25, 50, 100, 200 and 400 mJ/cm2, and sacrificed at 24, 48, 72 or 96 hours post-exposure. Histological evaluation and quantification of pro-inflammatory cytokines and chemokines (epidermis and dermis) was performed. The dose of UVr selected was 100 mJ/cm2, since it moderately increased pro-inflammatory cytokine and chemokine production (TNF-α, IL-6 and KC-1: 30, 80 and 1500 pg/mg protein, respectively, p<0,05 vs 0 mJ/cm2), promoted an inflammatory infiltrate (neutrophils) in the irradiated area (maximum 72 hs post-UVr) and produced just slight alterations of the skin architecture.To assess the potential of UVr as adjuvant therapy, mice were subcutaneously inoculated with 50 μl of MRSA (USA300LAC, 1x109 UFC/ml). Forty-eight hours post-inoculation, one group of mice was exposed to UVr, whereas the other remained as control. The infection was monitored by measuring the abscess size and mice weight daily for 14 days. UVr significantly reduced the area of the abscesses (89% of reduction at time 14 compared with time 0) whereas the non-irradiated group showed a reduction of 60% in the abscess size (p<0,05). UVr phototherapy may be a new strategy for MRSA treatment, since it promotes a local inflammatory response that favours neutrophil recruitment, necessary for bacterial clearance from the abscess and does not generate new antimicrobial resistance.