Abstract
The purpose of the study was to evaluate the antibacterial effect of protoporphyrin IX (PpIX) generated by the exogenous administration of 5-aminolevulinic acid or δ-ALA and activated with an argon laser over a planktonic and biofilm of Enterococcus faecalis (E. faecalis) as a pharmacological therapy alternative. A planktonic strain of E. faecalis was cultured with a solution of ∂-ALA (40 µg/mL)-thioglycolate solution for 13 min, and a biofilm of E. faecalis was cultured in a δ-ALA (80 µg/mL)-thioglycolate solution for 13 min. Then, both were irradiated with an argon laser. Finally, the antibacterial effect was evaluated by counting the CFU in planktonic form, and a LIVE/DEAD viability cell test. The production and accumulation of PpIX from exogenously administered δ-ALA on E. faecalis in planktonic and biofilm forms was confirmed by spectrofluorometry. The irradiation of PpIX with an argon laser produced an antibacterial effect on E. faecalis in planktonic and biofilm form, even without biofilm disruption, at a concentration of 40 µg/mL and 80 µg/mL of δ-ALA, respectively. The exogenous administration of δ-ALA in combination with laser irradiation on planktonic and biofilm forms of E. faecalis produces an effective antibacterial effect as complement or alternative to pharmacological therapies.
Highlights
Microbial infection remains among the leading causes of death worldwide (Barra et al, 2015)
The cell viability test evaluated by CTC of the biofilms treated with δ-ALA (80 μg/mL) and irradiated with an argon laser, 510 nm, 200 J/cm2, show a small number of bacteria compared with the groups not treated, demonstrating that the activation of protoporphyrin IX (PpIX) by a laser has an antibacterial effect, even without biofilm disruption (Figure 4)
The results obtained by spectrofluorometry verified that the δ-ALA administered to the microorganism is metabolically transformed in PpIX
Summary
Microbial infection remains among the leading causes of death worldwide (Barra et al, 2015). The variety of infections produced by Enterococci include urinary tract infections, intra-abdominal infections, pelvic infections (Gilmore et al, 2014), deviceassociated infections (Darouiche, 2001), soft tissue infections, bacteremia and endocarditis (Gilmore et al, 2014) Pathogenic bacteria, such as Enterococci, can attach to biotic or abiotic surfaces (Balcázar, Subirats, Borrego, 2015), forming a microbial community (Donlan, 2011; Li et al, 2013) in a three-dimensional extracellular polysaccharide matrix (EPM) (Balcázar, Subirats, Borrego, 2015; Barra et al, 2015; Li et al, 2013; López-Jiménez et al, 2015) known as a biofilm (Balcázar, Subirats, Borrego, 2015). The type I pathway forms superoxide anions that lead to the formation of reactive oxygen species (ROS), such as hydroxyl radicals, whereas the type II pathway leads to singlet oxygen production (Homayoni et al, 2015; Sperandio, Huang, Hamblin, 2013) Both processes produce a cytotoxic effect on bacteria (López-Jiménez et al, 2015; Pagonis et al, 2010). The aim of the present study was to determinate the antibacterial effect of the exogenous administration of δ-ALA to produce intracellular PpIX irradiated with an argon laser (500 mW, 510 nm, 200 J/cm2) on planktonic and biofilm forms of E. faecalis
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