Effects of photodynamic therapy on Enterococcus faecalis biofilms

Abstract

Microbial biofilms are involved in almost all infectious pathologies of the oral cavity. This has led to the search for novel therapies specifically aimed at biofilm elimination. In this study, we used atomic force microscopy (AFM) to visualize injuries and to determine surface roughness, as well as confocal laser scanning microscopy (CLSM) to enumerate live and dead bacterial cells, to determine the effects of photodynamic therapy (PDT) on Enterococcus faecalis biofilms. The AFM images showed that PDT consisting of methylene blue and a 670-nm diode laser (output power 280 mW during 30 s) or toluidine blue and a 628-nm LED light (output power 1000 mW during 30 s) induced severe damage, including cell lysis, to E. faecalis biofilms, with the former also causing an important increase in surface roughness. These observations were confirmed by the increase in dead cells determined using CLSM. Our results highlight the potential of PDT as a promising method to achieve successful oral disinfection.

Sub-lethal doses of photodynamic therapy affect biofilm formation ability and metabolic activity of Enterococcus faecalis

“…These observations were concomitant with the study conducted by López-Jiménez et al [13] which showed the susceptibility of E. faecalis to PDT. They suggested that the antibacterial activity is due to changes in membrane permeability, cell division machinery, and inhibition of bacterial cell wall synthesis.…”

“…As a result, any microorganism, such as E. faecalis, not eradicated and remaining viable at the site of infection would be exposed to doses of PDT that would not result in cell death, i.e., sub-lethal doses of PDT (sPDT), exposing survivors to ROS stress. ROS has been recognized to play an active and important role in processes such as cell death and biofilm/colony development in bacteria [13]. Previous studies have been shown that the exposure of bacteria to sPDT could lead to the extension of resistance to antimicrobial agents and result in an increased risk of poor clinical outcomes, and more consumption of medical resources [14,15].…”

Antimicrobial Photodynamic Therapy against Endodontic Enterococcus faecalis and Candida albicans Mono and Mixed Biofilms in the Presence of Photosensitizers: A Comparative Study with Classical Endodontic Irrigants

“…The presence of these inactive “ghost” cells was corroborated by the biomass loss assessed by SR assay. Before, it was described that E. faecalis elimination with aPDT resulted in bleb formations suggestive of damage of membrane components (López-Jiménez et al, 2015), shrunken, bacterial cell diameter reduction, rough and fractured appearance of the bacterial cells (Cheng et al, 2012). It was also described the presence of bacterial cell membrane shriveling and alterations including loss of cocci or bacilli shape, grooves on the cell surface and draining of the intracellular components (Garcez et al, 2013).…”

The antibacterial effect of sinoporphyrin sodium photodynamic therapy on Staphylococcus aureus planktonic and biofilm cultures

“…It has been reported that ROS contributes to the microbicidal activity of phagocytes, regulation of signal transduction and gene expression, and induces oxidative damage to nucleic acids, proteins, and lipids . Many evidences have demonstrated the importance of ROS in PDT treatment in both anticancer and antibacterial action . We next measured intracellular ROS generation in S. aureus after treatments.…”

“…To overcome the antibiotic resistance of biofilm bacteria and planktonic bacteria, more effective antimicrobial agents or new treatments are needed. In recent years, scholars have developed a series of new‐style antibacterial approaches such as nanomolecules , antimicrobial peptide , and photodynamic therapy (PDT) .…”