Changes of Microbial Cell Survival, Metabolic Activity, Efflux Capacity, and Quorum Sensing Ability of Aggregatibacter Actinomycetemcomitans Due to Antimicrobial Photodynamic Therapy-Induced Bystander Effects Publisher Pubmed



Mahdizadeari M¹ ; Pourhajibagher M² ; Bahador A¹ Show Affiliations
Source: Photodiagnosis and Photodynamic Therapy Published:2019

Abstract

Background: The bystander effects, whereby naive (bystander)microbial cells near microbial cells directly exposed to certain treatment show responses that would not have happened in the absence of the directly targeted microbial cells, is recently documented in the field of microbiology. In this article, we discuss that substantial bystander responses are also observed after antimicrobial photodynamic therapy (aPDT)using curcumin (Cur). Materials and methods: Bystander effects induced by whole bacterial cell suspension (WBCS T ), cell-free supernatants fluid (CFSF T ), and bacterial cell pellet (BCP T )obtained from A. actinomycetemcomitans culture treated with Cur-aPDT on cell survival, quorum sensing (QS)ability, metabolic activity and efflux capacity of A. actinomycetemcomitans were determined using microbial viability assay, Escherichia coli-based bioassay, XTT reduction method, and ethidium bromide (EtBr)accumulation assay, respectively. Results: A. actinomycetemcomitans cell survival reduced by 82.7% (P = 0.001)and 76.2% (P = 0.01)after exposure to WBCS T and CFSF T , respectively. The A. actinomycetemcomitans population increased by 5.5% (P = 0.7)after exposure to BCP T . Bacterial metabolic activity decreased by 42.6% (P = 0.02), 35.3% (P = 0.03), and 9.4% (P = 0.5)after exposure to WBCS T , CFSF T , and BCP T , respectively. A. actinomycetemcomitans exposed to WBCS T , CFSF T , and BCP T showed a reduction of 83.2% (P = 0.001), 77.2% (P = 0.01)and 21.9% (P = 0.09)in the QS mediator compared to the WBCS U , CFSF U , and BCP U of untreated A. actinomycetemcomitans, respectively. No significant change of the EtBr accumulation was observed in the three preparations of the Cur-aPDT-treated culture (i.e. WBCS T , CFSF T , and BCP T )compared to their respective controls. Conclusions: The results of the current study revealed that Cur-aPDT could significantly reduce microbial cell survival, cell metabolic activity, efflux capacity, and QS ability through the bystander effects. As a result, the bystander effects of Cur-aPDT along with the direct effect of Cur-aPDT can enhance the efficiency of aPDT as an adjunct therapeutic strategy for treatment of local infections. © 2019 Elsevier B.V.