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

ROBERTO SEBASTIÁN TOMÁS; GUSTAVO CALVO; MARIELA CESPEDES; DANIEL SÁENZ; GABRIELA DI VENOSA; ADRIANA CASAS; LEANDRO MAMONE

Congreso; Photodynamic Therapy and Photodiagnosis Update E-CONGRESS 2020; 2020

Photodynamic Inactivation (PDI) combines the action of a photosensitizer with visible light, generating radical species that cause inactivation of microorganisms. Near Infrared Therapy (NIRT) employs infrared light that delivers 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 main porphyrin accumulated is Coproporphyrin. The aim of this work was to employ a combination of NIRT and PDI as an alternative approach to increase PDI efficiency to eradicate biofilms of Staphylococcus aureus, a relevant 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 did not 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 by counting of CFU/ml.NIRT was performed with a 980 nm laser (Lumiia, Argentina) under conditions not raising the medium temperature over 35 ºC (30W, 30 sec, continuous mode; 30W, 150 sec, 4 Hz, 50 FWHM). Under these conditions, 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 of biofilm viability independently on the light source employed for PDI. Furthermore, NIRT+ ALA- PDT reduced 3-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 due to higher permeation of ALA induced by the photothermic effect. The combination of therapies has potential applications on biofilms growing on titanium implants.REFERENCES:[1] Amos-Tautua B., Songca S., Oluwafemi O. (2019) Application of Porphyrins in AntibacterialPhotodynamic Therapy, Molecules 24(13): 2456.[2] Ibelli T., Templeton S., Levi-Polyachenko N. (2018) Progress on utilizing hyperthermia for mitigating bacterial infections, International Journal of Hyperthermia 34(2): 144-156.