A clinical study of photodynamic therapy for chronic skin ulcers in lower limbs infected with Pseudomonas aeruginosa

The objective of this study is to evaluate the antimicrobial activity and healing-promoting effect of topical photodynamic therapy (ALA-PDT) on chronic skin ulcers infected with Pseudomonas aeruginosa (PA). A total of 26 patients with chronic skin ulcers in lower limbs infected with PA were enrolled. The surface areas of the ulcers were treated with either δ-aminolevulinic acid (ALA)-mediated PDT (20 % ALA solution, 1.5 h incubation, 630 nm red light, 80 J/cm 2 ) or red light alone, both once a week for two weeks. Before treatment, the wound areas and the bacteria levels in these two groups were comparable ( p > 0.05). Results indicated that the bacteria levels in the skin ulcers of the light only group of 24 h post-treatment (3.4 × 10 7 ± 7.1 × 10 7 CFU/cm 2 ) and pre-treatment (5.5 × 10 7 ± 1.6 × 10 8 CFU/cm 2 ) were not significantly different. In contrast, the bacteria levels on the surfaces of the ulcers in the PDT group of 24 h post-treatment (6.3 × 10 5 ± 1.7 × 10 6 CFU/cm 2 ) and pre-treatment (8.9 × 10 7 ± 1.7 × 10 8 CFU/cm 2 ) were significantly different ( p < 0.01). At seven days post treatment, the mean ulcer area in the red light group was reduced from 11.85 ± 6.83 to 7.8 ± 4.9 cm 2 ( p < 0.01), that of PDT group from 12.72 ± 8.58 to 3.4 ± 3.4 cm 2 ( p < 0.01). Better healing was seen in PDT group ( p < 0.01). In conclusion, ALA-PDT is a potential modality to control PA infection and promote healing of chronic skin ulcers in lower limbs.