CONICET | Buscador de Institutos y Recursos Humanos

Pseudomonas aeruginosa is the cause of various infections. Amongst others, eye and ear infections or those in skin tissue and soft in burn patients represent a major therapeutic challenge. In recent years, photodynamic inactivation (PDI) has been proposed as an alternative treatment for localized bacterial infections in response to the problem of antibiotic resistance. The principle of PDI is to use a non-toxic dye or photosensitizer (PS) to produce reactive oxygen species (ROS) to cause damages on target bacteria while the PS is activated by a harmless visible light. The main purpose of this study was to explore the PDI effect of 5,10,15,20-tetra(4-N-methylpyridyl)porphyrin (TPMyP4+) on P.aeruginosa ATCC 27853 and a clinical isolate of MDR P.aeruginosa since reports of their effects against multi-drug resistant (MDR) bacteria are limited. The porphyrin was evaluated for different doses (2.5, 5, 10, 20 µM), 30 min of irradiation with visible light and cellular suspensions of ~ 1x106 CFU/mL. The PS was not toxic in absence of light for any doses studied. PDI treatment performed against both P.aeruginosa strains show a similar performance for all concentrations tested. Cellular suspension treated with 10 µM of TMPyP4+ reached an inactivation greater than 99.99% for both strains. Moreover the assay was carried out incubating cells 30 min with porphyrin before irradiation and without this step. As previously, the inactivation was greater than 99.99%. Therefore, the sensitizer is quickly bound to the bacterial cell, thus reducing the treatment time. Additional experiments will be needed to confirm this hypothesis. TMPyP4+proved equally effective for photodynamic inactivation of P. aeruginosa both sensitive and resistant to antimicrobial agents currently used in therapeutics. This reinforces the potential utility of Photodynamic Antimicrobial Chemotherapy as an alternative to the global problem of antimicrobial resistance.