Synergistic effect of carboxypterin and methylene blue applied to antimicrobial photodynamic therapy against mature biofilm of Klebsiella pneumoniae

GASPAR TOSATO, MAIRA; SCHILARDI, P.L; FERNANDEZ LORENZO DE MELE, M; THOMAS, A; LORENTE, CAROLINA; MIÑÁN ALEJANDRO

Heliyon

Elsevier

Año: 2020

2405-8440

The control of multidrug-resistant (MDR) bacteria is a growing public health problem, and new strategies are urgently needed for the control of the infections caused by these microorganisms. Notoriously, some MDR microorganisms generate complex structures or biofilms, which adhere to surfaces and confer extraordinary resistance properties that are fundamental challenges to control infections.One of the promising strategies for the control of MDR bacteria is antimicrobial photodynamic therapy (aPDT), which takes advantage of suitable photosensitizers (PS), oxygen and radiation to eradicate microorganisms by the generation of highly reactive species, including reactive oxygen species (ROS) that cause cytotoxic damage and cell death. Habitual PDI treatments use only methylene blue, but MDR microorganism eradication is not completely achieved.The key result of this study revealed that a combination of two known PSs, 6-carboxypterin (Cap, 100 M) and methylene blue (MB, 2.5-10 M) exposed to ultraviolet and visible radiation, presents a synergistic effect on the eradication of a MDR Klebsiella pneumoniae strain. Similar effect was observed when the treatment was performed either with planktonic or biofilm growing cells. Moreover, it was found that after treatment the killing action continues in the absence of irradiation leading to the eradication of the microorganisms growing in a biofilm.