A dual-species microbial model for studying the dynamics between oral streptococci and periodontal pathogens during biofilm development on titanium surfaces by flow cytometry

Phage-based biocontrol of Porphyromonas gingivalis through indirect targeting

Bacteriophages offer an opportunity for chemical-free, precise control of problematic bacteria, but this approach can be limited when lytic phages are difficult to obtain for the target host. In such cases, phage-based targeting of cooperating or cross-feeding bacteria (e.g., Streptococcus gordonii) can be an effective approach to control the problematic bacteria (e.g., Porphyromonas gingivalis). Using a dual-species biofilm system, phage predation of S. gordonii (108 PFU·mL-1) decreased the abundance of pathogenic P. gingivalis by >99% compared with no-treatment controls, while also inhibiting the production of cytotoxic metabolic end products (butyric and propionic acids). Phage treatment upregulated genes associated with interspecies co-adhesion (5- to 8-fold) and quorum sensing (10-fold) in residual P. gingivalis, which is conducive to increased potential to bind to S. gordonii. Counterintuitively, lower-titer phage applications (104 PFU·mL-1) increased the production of extracellular polymeric substance (EPS) by 22% and biofilm biomass by 50%. This overproduction of EPS may contribute to the phenomenon where the biofilm separated into two distinct species layers, as observed by confocal laser scanning microscopy. Although more complex mixed-culture systems should be considered to delineate the merits and limitations of this novel biocontrol approach (which would likely require the use of phage cocktails), our results offer proof of concept that indirect phage-based targeting can expand the applicability of phage-based control of pathogenic bacteria for public health protection.

IMPORTANCE

Lytic phages are valuable agents for targeted elimination of bacteria in diverse applications. Nevertheless, lytic phages are difficult to isolate for some target pathogens. We offer proof of concept that this limitation may be overcome via indirect phage targeting, which involves knocking out species that interact closely with and benefit the primary problematic target bacteria. Our target (P. gingivalis) only forms a periodontal pathogenic biofilm if the pioneer colonizer (S. gordonii) offers its surface for P. gingivalis to attach. Phage predation of the co-adhesive S. gordonii significantly reduced abundance of the target pathogen by >99%, decreased the total biofilm biomass by >44%, and suppressed its production of cytotoxic metabolic byproducts. Thus, this research extends the scope of phage-based biocontrol for public health protection.

Efficient Removal of Dental Plaque Biofilm from Training Typodont Teeth via Water Flosser

Plaque biofilms play critical roles in the development of dental caries. Mechanical plaque control methods are considered to be most effective for plaque removal, such as brushing teeth or using flosser. Recently, water flosser has been paid much attention. Here, we tested the ability of a water flosser to remove the adhered sucrose and the dental plaque biofilms formed by Streptococcus mutans, Streptococcus sanguinis, and Actinobacillus viscosus. We found that the residual sucrose concentration was 3.54 mg/mL in the control group, 1.75 mg/mL in the syringe group (simulating the ordinary mouthwash), and 0 mg/mL in water flosser group. In addition, the residual bacterial concentration was 3.6 × 108 CFU/mL in the control group, 1.6 × 107 CFU/mL in the syringe group, and only 5.5 × 105 CFU/mL in the water flosser group. In summary, water flosser is effective for cleaning the teeth, which may have significant potential in preventing dental caries and maintaining oral health.

Effect of curcumin-loaded photoactivatable polymeric nanoparticle on peri-implantitis-related biofilm

Curcumin has been used as a photosensitizer (PS) for antimicrobial photodynamic chemotherapy (PACT). However, its low solubility, instability, and poor bioavailability challenge its in vivo application. This study aimed to synthesize curcumin-loaded polymeric nanoparticles (curcumin-NP) and determine their antimicrobial and cytotoxic effects. Nanoparticles (NP) were synthesized using polycaprolactone (PCL) as a polymer by the nanoprecipitation method. Curcumin-NP was characterized by particle size, polydispersity index and zeta potential, scanning electron microscopy, and curcumin encapsulation efficiency (EE). Curcumin-NP was compared to free curcumin solubilized in 10% DMSO as photosensitizers for PACT in single and multispecies Porphyromonas gingivalis, Fusobacterium nucleatum, and Streptococcus oralis biofilms. Chlorhexidine 0.12% (CHX) and ultrapure water were used as positive and negative controls. The cytotoxic effect of curcumin-NP was evaluated on human periodontal ligament fibroblast cells (HPLF). Data were analyzed by ANOVA (α=0.05). Curcumin-NP exhibited homogeneity and stability in solution, small particle size, and 67.5% EE of curcumin. Curcumin-NP presented reduced antibiofilm activity at 500 µg/ml, although in planktonic cultures it showed inhibitory and bactericidal effect. Curcumin-NP and curcumin with and without photoactivation were not cytotoxic to HPLF cells. Curcumin-NP has antimicrobial and antibiofilm properties, with better effects when associated with blue light, being a promising therapy for preventing and treating peri-implant diseases.

Antibiofilm effect of ozonized physiological saline solution on peri-implant-related biofilm

BACKGROUND

Removal of dental plaque and local application of local chemical adjuncts, such as chlorhexidine (CHX), have been used to control and treat peri-implant disease. However, these methods can damage the surface properties of the implants or promote bacterial resistance. The application of ozone as an adjunctive treatment represents a new approach in the management of peri-implantitis. Thus, the purpose of this study was to evaluate the antimicrobial effect of ozonized physiological saline solution in different concentrations against oral biofilms developed on titanium surface.

METHODS

Single and multi-species biofilms of Porphyromonas gingivalis, Fusobacterium nucleatum, and Streptococcus oralis were formed on titanium specimens for 5 days in anaerobic conditions. Biofilms were treated with ozonized saline solution at different concentrations (25, 50, and 80 μg/NmL), for 30 seconds and 1 minute. CHX (0.12%) and saline solution (0.89% NaCl) were used as positive and negative controls, respectively. Bacterial viability was quantified by colony forming units (CFU mL^-1 ), and biofilm images were acquired by confocal laser scanning microscopy (CLSM). Data were analyzed by parametric test (ANOVA) with Tukey post-hoc test (P < 0.05).

RESULTS

Ozonized saline solution showed antibiofilm activity at a concentration of 80 μg/NmL for 30 seconds and 1 minute, reducing, mainly, Porphyromonas gingivalis viability, with 2.78 and 1.7 log₁₀ CFU mL^-1 of reduction in both single and multi-species biofilms, respectively, when compared to the control (saline), whereas CHX reduced 1.4 and 1.2 log₁₀ CFU mL^-1 .

CONCLUSION

Ozonized saline solution has antibiofilm activity, with better effect when applied for 1 minute at 80 μg/NmL, being a promising candidate therapy for the treatment of peri-implant diseases.