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 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).
Conclusion: 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.