Near-Infrared laser enhances Coproporphyrin formation from ALA in Staphylococcus biofilms

TOMÁS, R; SAENZ, D; MAMONE, L; CALVO, G; DI VENOSA, G; CÉSPEDES, M; CASAS, A

virtual

Congreso; Photodynamic Therapy & Photodiagnosis Update 2020 E-congress; 2020

Committee of the Conference Photodynamic Therapy and Photodiagnosis ? Update 2020

Photodynamic Inactivation (PDI) combines the action of a photosensitizer with visible light, generating radicalspecies that cause inactivation of microorganisms. Near Infrared Therapy (NIRT) employs infrared light thatdelivers thermal energy to the organisms, exciting water molecules and bacterial cromophores.The 5-aminolevulinic acid (ALA) is a precursor in endogenous biosynthesis of porphyrins. After itsincorporation into bacterial cells, an increase in porphyrin levels is produced. In Staphylococci, the mainporphyrin accumulated is Coproporphyrin. The aim of this work was to employ a combination of NIRT andPDI as an alternative approach to increase PDI efficiency to eradicate biofilms of Staphylococcus aureus, arelevant human opportunistic pathogen.Response to PDI of S. aureus biofilms grown on polystyrene surface was determined after incubation with ALA(2mM) and irradiation with non-coherent visible light (58 J/cm2; quartz halogen lamps, GE). This treatment didnot induce any significant effect on biofilm viability. However, employing a 635 nm laser (96 J/cm², Lumiia,Argentina), a 1-logdecrease on biofilm viability was observed. Viability after treatments was evaluated bycounting of CFU/ml.NIRT was performed with a 980 nm laser (Lumiia, Argentina) under conditions not raising the mediumtemperature over 35 ºC (30W, 30 sec, continuous mode; 30W, 150 sec, 4 Hz, 50 FWHM). Under theseconditions, NIRT did not modify biofilm viability. However, in biofilms exposed to ALA, NIRT induced a 25%increase in Coproporphyrin levels.Biofilms growing on polystyrene sequentially treated with NIRT and ALA-PDI suffered a 1-log reduction ofbiofilm viability independently on the light source employed for PDI. Furthermore, NIRT + ALA- PDT reduced3-logs the viability of S. aureus biofilms growing on titanium surfaces.The synergistic action of NIRT on ALA-PDI is presumably ascribed to the increase of bacterial porphyrins dueto higher permeation of ALA induced by the photothermic effect. The combination of therapies has potentialapplications on biofilms growing on titanium implants.