Light Fractionation Consents For Enhancement Of Photodynamic Therapy In Streptococcus Mutes Biofilm

Abstract

Microbial infections continue to be a major cause of death. The culprit is biofilm that forms multiple drug-resistant strains of bacteria. Biofilms are the three-dimensional, surface-attached structure of heteromorphic microorganisms embedded in extracellular polymeric substances (EPS). The main antibiotic resistance mechanisms in biofilm-associated bacteria are antibiotic penetration, efflux and production. They prevent drug access to the cell's interior. To avoid the severe biofilm-related infections, it is urgent to look into novel treatments like photodynamic therapy (PDT).This study was initiated to examine the photo-inactivation efficiency and effect of reactive oxygen substances (ROS) on Gram positive and negative bacterial cells as well as their biofilm. Each dye was photo activated at a 10uM level using 630nm laser light. This light was used to kill Klebsiella pneumoniae and Enterococcus foecalis. E. faecalis showed a reduction of 8log10 bacterial counts, while K. pneumoniae saw a reduction of 3log10. Photodynamic inhibition was more prominent in Gram positive bacteria, according to antibiofilm and extracellular polysaccharides reduction assay.This was in addition to the results of confocal laser microscopy, (CLSM), and scanning electron microscopywhich showed an increase of cell permeability of propionidium iodide in cells. Also, there was a leakage of cellular constituents within preformed biofilm that had been treated with photodynamic therapy. This is a reflection of the antibiofilm effect of photodynamic treatment. The increased ROS production in Gram positive bacteria cells was confirmed by fluorescence spectroscopic analysis. Results showed that Gram positive bacteria (E.faecalis), are more vulnerable to PDT because of increased ROS generation, higher photosensitizer binding efficacy and DNA degradation. The efficacy of phenothiazinium dyes against planktonic as well as biofilm cells has been proven. We conclude that Gram positive bacteria (Enterococcus foecalis) are more vulnerable to APDT because of higher ROS generation, increased photosensitizer binding efficacy and DNA degradation. The efficacy of phenothiazinium dyes against planktonic as well as biofilm cells has been proven.