Zinc enhances the phototoxic effect of blue light against malodour-producing bacteria in an experimental oral biofilm

Abstract

Oral malodour is thought to be caused mainly by the production of volatile sulfide compounds (VSCs) by anaerobic Gram-negative oral bacteria. Previous studies have shown that these bacteria are susceptible to blue light (400-500 nm wavelength). In the present study, we tested the effect of blue light in the presence of zinc, erythrosine B or both on malodour production in an experimental oral biofilm. Biofilms were exposed to a plasma-arc light source for 30, 60 and 120 s (equal to energy fluxes of 41, 82 and 164 J cm "2 , respectively) with or without the addition of zinc acetate, erythrosine B or both. After the light exposure, biofilm samples were examined for malodour production (by an odour judge) and VSC production (with a Halimeter), and VSCproducing bacteria were quantified using a microscopy-based sulfide assay (MSA) and in situ confocal laser scanning microscopy (CLSM). Results showed that exposing experimental oral biofilm to both blue light and zinc reduced malodour production, which coincided with a reduction in VSC-producing bacteria in the biofilm. These results suggest that zinc enhances the phototoxicity of blue light against malodour-producing bacteria.

Effect of red dyes on blue light phototoxicity against VSC producing bacteria in an experimental oral biofilm

“…Previous studies demonstrated the phototoxic effect of high intensity blue light against malodour producing bacteria in a salivary incubation assay [13]. This effect was enhanced in the presence of zinc serving as a possible photocatalytic agent [16]. In the present study, we tested the effect of various red dyes photosensitizers on this process in an experimental biofilm system.…”

“…In previous studies we showed that VSC producing bacteria were suseptible to high intensity blue light [13] and that this phototoxic effect was enhanced by the addition of zinc ions [16]. The aim of the present study was to test the hypothesis that red dye photosensitizers may promote the phototoxic effect of high intensity blue light against malodor producing bacteria in an experimental oral biofilm model.…”

Antimicrobial blue light inactivation of pathogenic microbes: State of the art

“…They also possess mild antibacterial effects. Sterer et al reported that zinc acetate enhanced the effectiveness of aBL against malodour-producing bacteria in an experimental oral biofilm (Sterer et al, 2014). Biofilms were exposed to aBL (400–500 nm) at the exposures of 41, 82, and 164 J/cm 2 , respectively with or without the addition of zinc acetate.…”

Resistance of Bacteria toward 475 nm Blue Light Exposure and the Possible Role of the SOS Response

“…First, zinc acetate (ZnAc) has been shown to inhibit ciprofloxacin- as well as zidovudine-induced recA gene expression at 200 µM in a Shiga toxin-producing E. coli strain [ 33 ]. Sterer et al found that adding 1 % ( w / v ) of ZnAc when irradiating a biofilm with a light source emitting a wavelength of 400–500 nm and a dose of 41, 82 and 164 J/cm 2 increased the inactivation of malodor-producing bacteria compared to aBL treatment alone [ 60 ]. In the present work, 475 nm aBL therapy was performed with a concentration of 500 µM ZnAc with E. coli K12 and E. coli TOP10.…”