Photodynamic inactivation from ALA, on bacterial infections and skin wounds in an in vivo mouse model.

TOMÁS RS; DI VENOSA G; BUZZOLA FR; CASAS A; MAMONE L

Congreso; LXVII ANNUAL MEETING OF SOCIEDAD ARGENTINA DE INVESTIGACIÓN CLÍNICA (SAIC); 2022

Photodynamic Inactivation (PDI) is a treatment that uses a photosensitizingcompound (PS) that after absorbing visible light in thepresence of molecular oxygen generates reactive oxygen species,which cause damage and inactivation of microorganisms. 5-aminolevulinicacid (ALA) is a precursor in the biosynthesisof porphyrins,some of which can act as PSs in both eukaryotic cells and bacteria.The objective of this work was to evaluate the effect of ALA-PDI(visible light irradiation after topical ALA treatment) on the progressionof wounds caused by Staphylococcus aureus infection, in anin vivo model in mice. CF1 mice were injected subcutaneously witha suspension of S. aureus RN6390. After 48 h, 20 mg/ml ALA solutionwas applied to the skin, in the area of infection, 4 h later, fluorescenceemitted by the synthesized porphyrins was detected. ThePDI was performed employing a 635 nm laser device. The effect ofALA-PDI was determined by measuring the area of wound (causedby infection) during four weeks after treatment. Porphyrins wereidentified by fluorescence spectroscopy. The effects of ALA-PDI onthe bacteria present in the infection were determined by measuringCFUs from skin homogenates. Infected skins showed a higher productionof porphyrins than non-infected. The main porphyrin synthesizedwas protoporphyrin IX. Wounds treated with ALA-PDI beganto reducearea immediately after irradiation(in contrast to untreatedor only irradiated controls). Time required to fully closure wounds inthe ALA-PDI group was significantly less (p˂0.01) than in untreatedcontrols (14 vs 27 days). In addition, it was observed that irradiatedcontrols without ALA, also reduced the area of the wounds earlierthan untreated controls. By employing an alternative model of uninfectedskin wound, this effect of laser irradiation on wound healingwas corroborated. Results suggest that PDI employing ALA as aprecursor of PSs porphyrins is a promising option to treat superficialinfections.