Changes of microbial cell survival, metabolic activity, efflux capacity, and quorum sensing ability of Aggregatibacter actinomycetemcomitans due to antimicrobial photodynamic therapy-induced bystander effects

Background: Photoactivated disinfection (PAD) has been indicated as one of the potential methods for the initial periodontal therapy in periodontitis and peri-implantitis, which may have the bystander effects on the viability of off-target cells. Objective: In this article, we evaluated the effects of PAD-induced bystander on biofilm formation ability, metabolic activity, and gene expression level of Aggregatibacter actinomycetemcomitans as one of the bacteria involved in causing periodontitis and peri-implantitis. Methods: Bystander effects induced by bacterial cell suspension (BCST ) obtained from treated A. actinomycetemcomitans culture with indocyanine green (ICG)-PAD on biofilm formation of A. actinomycetemcomitans were determined using microbial viability assay. Additionally, metabolic activity and changes in gene expression of fimA were assessed using the XTT reduction method and quantitative real-time PCR (qRT-PCR) assay, respectively. Results: The results revealed that 1000 and 125 μg/mL of ICG combined with diode laser irradiation for 1 min were significant and sub-significant reduction doses of ICG-PAD, respectively versus A. actinomycetemcomitans. The biofilm formation ability, metabolic activity, as well as, expression level of fimA gene in A. actinomycetemcomitans were significantly reduced after treatment by a significant reduction dose of ICG-PAD-induced bystander effects (P<0.05). Conclusions: ICG-PAD could significantly reduce the microbial population, cell metabolic activity, and gene expression through the bystander effects and could enhance the efficiency of PAD as an adjunct approach for the nonsurgical treatment of periodontitis and peri-implantitis.

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Effect of Antimicrobial Photodynamic Therapy Using Indocyanine Green Doped with Chitosan Nanoparticles on Biofilm Formation-Related Gene Expression of Aggregatibacter actinomycetemcomitans

Frontiers in Dentistry ◽

10.18502/fid.v16i3.1590 ◽

2019 ◽

Author(s):

Mehdi Rostami Rad ◽

Maryam Pourhajibagher ◽

Amir Reza Reza Rokn ◽

Hamid Reza Barikani ◽

Abbas Bahador

Keyword(s):

Gene Expression ◽

Photodynamic Therapy ◽

Indocyanine Green ◽

Diode Laser ◽

Virulence Factor ◽

Biofilm Formation ◽

Chitosan Nanoparticles ◽

Aggregatibacter Actinomycetemcomitans ◽

Expression Level ◽

Antimicrobial Photodynamic Therapy

Objectives: Eradication of Aggregatibacter actinomycetemcomitans (A. action-mycetemcomitans), as an opportunistic periodontopathogen, and inhibition of its virulence factor expression require a new adjunctive therapeutic method. In this study, we accessed the expression level of rcpA gene, as a virulence factor associated with A. actinomycetemcomitans biofilm formation, following treatment by antimicrobial photodynamic therapy (aPDT) using indocyanine green (ICG) doped with chitosan nanoparticles (CS-NPs@ICG). Materials and Methods: CS-NPs@ICG was synthesized and examined using scanning electron microscopy (SEM). A. actinomycetemcomitans ATCC 33384 strain was treated with CS-NPs@ICG, as a photosensitizer, which was excited with a diode laser at the wavelength of 810 nm with the energy density of 31.2 J/cm2. Quantitative real-time polymerase chain reaction (qRT-PCR) was performed to determine the changes in rcpA gene expression level. Results: Synthetized CS-NPs@ICG was confirmed via SEM. The results revealed that CS-NPs@ICG-mediated aPDT could significantly decrease rcpA gene expression to 13.2-fold (P<0.05). There was a remarkable difference between aPDT using CS-NPs@ICG and ICG (P<0.05). The diode laser, ICG, and CS-NPs@ICG were unable to significantly downregulate rcpA gene expression (P>0.05). Conclusion: aPDT with CS-NPs@ICG leads to a decrease of the virulence factor of A. actinomycetemcomitans and can be used as an adjunct to routine treatments for successful periodontal therapy in vivo.

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