Effects of photodynamic therapy on Enterococcus faecalis biofilms.

L López-Jiménez,J Arnabat-Domínguez,M Viñas,T Vinuesa,E Fusté,B Martínez-Garriga

doi:10.1007/s10103-015-1749-y

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.

Highlights

A microbial biofilm is a three-dimensional, complex structure attached to a surface or interface and comprising microorganisms embedded in an extracellular polymeric matrix [1]
We examined the effects of photodynamic therapy (PDT) on biofilms of Enterococcus faecalis, a gram-positive bacterium resistant to some antibiotics and frequently found in the oral cavity of patients who have undergone root canal treatment
Live bacteria stain with Syto 9 to produce a green fluorescence whereas bacteria with compromised membranes stain with propidium iodide to produce a red fluorescence

Summary

Introduction

A microbial biofilm is a three-dimensional, complex structure attached to a surface or interface and comprising microorganisms embedded in an extracellular polymeric matrix [1]. An excellent example is oral biofilms, referred to as dental plaques [3, 4]. These typically contain an enormous variety of bacterial species, many of which are responsible for infections in the oral cavity and even elsewhere in the body [2]. Periodontal diseases, endodontic infections, and numerous pathologies beyond the oral cavity have been attributed to the proliferation of oral bacteria and their ability to form and participate in stable polymicrobial biofilms. Bacteria in biofilms are typically much more resistant to antimicrobials than their planktonic counterparts [6], the latter are used in the clinical testing of susceptibility

Methods

Results

Conclusion