Effects of Photodynamic Therapy on Gram-Positive and Gram-Negative Bacterial Biofilms by Bioluminescence Imaging and Scanning Electron Microscopic Analysis

Abstract

The photodynamic effect seems to disrupt the biofilm by acting both on bacterial cells and on the extracellular matrix.

Enterococcus faecium and Enterococcus faecalis in endodontic infections: antibiotic resistance profile and susceptibility to photodynamic therapy

“…Based on this context, various studies have been developed to investigate the efficacy of alternative approaches against E. faecalis, including antimicrobial photodynamic therapy (PDT) [16][17][18][20][21][22][23][24][25]. PDT is a therapeutic strategy that involves the combination of a nontoxic photosensitizer (PS) and a harmless visible light source [19].…”

“…For this reason, the action of different PSs has been the subject of widespread research, mainly phenothiazine dyes, porphyrins, and phthalocyanines [22]. Currently, the association of methylene blue (MB), with lasers at red wavelengths (600-700 nm), has been widely used for bacterial management in endodontic treatment by PDT [16][17][18][20][21][22][23][24][25]. In the presence of a light source, permeability to MB can vary according to the structural components present on the surface of the microorganisms, reducing their antimicrobial effects.…”

“…This is due to differences in the physiology of these microorganisms, since Gram-positive bacteria have a relatively porous outer membrane formed by a thicker layer of peptidoglycan and lipoteichoic acid. This feature allows a greater diffusion of the MB within the microbial cells, since they can be eliminated by lower concentration of this dye and lower doses of radiation, which explains the greater susceptibility of E. faecalis to PDT [20][21][22][23][24][25]. On the other hand, the outer membrane of Gram-negative bacteria is thinner and complex, being formed by a heterogeneous composition of proteins with porin function, lipopolysaccharides, and lipoproteins.…”

“…In vitro [16][17][18][20][21][22][23][24][25] and clinical [31] studies have supported the use of PDT to eliminate microorganisms in a root canal, particularly E. faecalis, a multiple drug resistance microorganism often associated with endodontic treatment failure. Although the role of E. faecalis in endodontic infections had been extensively studied, little is known about the presence of E. faecium and its role in endodontic infections.…”

Efeitos da Terapia Fotodinâmica mediada por laser de emissão vermelha e azul de metileno em vaginite induzida por Candida albicans

“…De fato, desde os últimos anos do século passado, junto às pesquisas da TFD antineoplásica, estudos sobre a terapia fotodinâmica antimicrobiana vêm sendo realizados, apresentando bons resultados de inativação microbiana, tanto em bactérias (WAINWRIGHT, 1998;DEMINOVA e HAMBLIM, 2004;PRATES et al, 2007;GARCEZ et al, 2013), como em fungos (GIROLDO et al, 2009;DOVIGO et al, 2010e 2011) e protozoários (BARBOSA et al, 2012 usando também, outras substâncias fotossensibilizadoras além do AM, como azul de toluidina, verde malaquita, eritrosina (VILELA et al, 2012;SOUZA, R. et al, 2010, LEE et al 2012.…”