Assessment of the Antibacterial Effects of Bismuth Nanoparticles against Enterococcus faecalis

Abstract

Introduction. Enterococcus faecalis (E. faecalis) is the most important species in dentistry and plays a significant role in the etiology of persistent apical lesions after root canal treatment. Up to date, the intracanal application of 2% chlorhexidine for 7 days is the best way to eliminate E. faecalis. However, due to the ability of this bacterium to persist and survive in harsh environments, many studies have been directed towards finding an alternative strategy for prevention or eradication of it. This study was conducted to investigate the effect of bismuth nanoparticles on E. faecalis, as an etiologic factor in recurrent root canal infections. Methods. Forty patients, referred to Endodontic Ward of Shiraz University of Medical Science for endodontic pretreatment, provided root canal samples. First, all samples were transferred in Enterococcosel broth and incubated. Then, samples which showed growth were plated on blood agar plates and incubated for further PCR procedure. Nanoparticle powder was dissolved in high-purity water, and the final concentration of bismuth nanoparticles (BiNPs) was measured by the spectrophotometer. Minimum inhibitory concentration (MIC) of BiNPs against E. faecalis was determined by microbroth dilution method according to methods for antimicrobial susceptibility tests. Also, bactericidal assays were conducted in Mueller-Hinton broth medium and reported as the concentration of BiNPs that reduced the viable bacterial count by 99.9%. Results. Of all samples, 77.5% revealed the presence of E. faecalis by PCR. Also, E. faecalis growth inhibition was observed at concentrations ranging from 0.625 μg/ml to 20 μg/ml (geometric mean: 2.337 μg/ml), and the MBC values were between 1.25 μg/ml and 40 μg/ml (geometric mean: 4.781 μg/ml), which in comparison with chlorhexidine, these values were about one-eighth of chlorhexidine. Conclusion. The experimental data suggest that bismuth nanoparticles could be an interesting alternative to combat E. faecalis, which, in view of the advantages mentioned for bismuth nanoparticle like inhibiting Streptococcus mutans biofilm formation and higher antibacterial activity compared to chlorhexidine, can be suggested to be used in different fields of dentistry.

New Strategy of Reducing Biofilm Forming Bacteria in Oral Cavity by Bismuth Nanoparticles

“…Forty patients, ages from 18 to 45 years old, including 22 males and 18 females, referred to the Endodontic Ward of Shiraz University of Medical Science for endodontic pretreatment, provided root canal samples, which were then analyzed for the presence of E. faecalis and S. salivarius . All samples were obtained from patients who had rooted canal therapy completed more than 1 year ago [ 21 ]. Patients who were pregnant, diabetic, and smokers and those requiring pretreatment due to missing canals, broken instruments, perforations, ledges, or calcified root canals were excluded.…”

“…The study was approved by the Ethics Committee of Shiraz University of Medical Science IR.sums.dental.rec.1399.119). Patients were informed of the study procedures and goals, and written consent was obtained [ 21 ].…”

“…The mixture was divided into several plates containing blood agar medium. The plates were incubated at 37°C [ 21 ].…”

“…Several colonies of bacteria were dissolved in 1 cc of physiological serum. Turbidity of bacterial solution was compared with the standard 0.5 McFarland solution [ 21 ].…”

“…The sonicated solution was sterilized by passing through a 0.2 μ m filter (Control Biogene, Spain), and the final concentration of BiNPs was measured with a spectrophotometer (Eppendrof, Germany). The shape, size, and distribution of BiNPs have been characterized by the high-resolution transmission electron microscopy (TEM) with a JEM-1011 microscope (JEM-1011 “JEOL Ltd.,” Japan) [ 21 ].…”