Investigation of a novel biofilm model close to the original oral microbiome.

A more optimized culture medium used in vitro to mimic the bacterial composition of original oral flora as similar as possible remains difficult at present, and the goal of this study is to develop a novel oral biofilm medium to restore the original oral microbiome. Firstly, we conducted a systematic literature review by searching PubMed and summarized the current reported culture media in vitro. Seven culture media were found. We used mixed saliva as the origin of oral species to compare the effects of the above media in culturing oral multispecies biofilms. Results indicated that among the seven media brain heart infusion containing 1% sucrose (BHIs) medium, PG medium, artificial saliva (AS) medium, and SHI medium could obviously gain large oral biofilm in vitro. The nutrients contained in different culture media may be suitable for the growth of different oral bacteria; therefore, we optimized several novel media accordingly. Notably, results of crystal violet staining showed that the biofilm cultured in our modified artificial saliva (MAS) medium had the highest amount of biofilm biomass. 16S rRNA gene sequencing showed that the operational taxonomic units (OTUs) and Shannon index of biofilm cultured in MAS medium were also the highest among all the tested media. More importantly, the 16S rRNA gene sequencing analysis indicated that the biofilm cultured in MAS medium was closer to the original saliva species. Besides, biofilm cultured by MAS was denser and produced more exopolysaccharides. MAS supported stable biofilm formation on different substrata. In conclusion, this study demonstrated a novel MAS medium that could culture oral biofilm in vitro closer to the original oral microbiome, showing a good application prospect. KEY POINTS: • We compare the effects of different media in culturing oral biofilms • A novel modified artificial saliva (MAS) medium was obtained in our study • The MAS medium could culture biofilm that was closer to oral microbiome.

Anti-Bacteria and Microecosystem-Regulating Effects of Dental Implant Coated with Dimethylaminododecyl Methacrylate.

The effects of dimethylaminododecyl methacrylate (DMADDM) modified titanium implants on bacterial activity and microbial ecosystem of saliva-derived biofilm were investigated for the first time. Titanium discs were coated with DMADDM solutions at mass fractions of 0 mg/mL (control), 1, 5 and 10 mg/mL, respectively. Biomass accumulation and metabolic activity of biofilms were tested using crystal violet assay and MTT (3-(4,5-Dimethyl-thiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay. 16S rRNA gene sequencing was performed to measure the microbial community. Live/dead staining and scanning electron microscopy (SEM) were used to value the structure of biofilm. The results showed that the higher mass fraction of DMADDM the coating solution had, the significantly lower the values of metabolic activity and accumulated biofilms got, as well as fewer live cells and less extracellular matrix. Moreover, 5 mg/mL of DMADDM was the most effective concentration, as well as 10 mg/mL. In microecosystem-regulation, the DMADDM modified titanium implant decreased the relative abundance of Neisseria and Actinomyces and increased the relative abundance of Lactobacillus, a probiotic for peri-implant diseases. In conclusion, via inhibiting growth and regulating microecosystem of biofilm, this novel titanium implant coating with DMADDM was promising in preventing peri-implant disease in an 'ecological manner'.

Effects of different substrates/growth media on microbial community of saliva-derived biofilm.

The aims of this study were to investigate the effects of substrates (glass versus hydroxyapatite [HA]) and growth media (SHI medium versus a modified artificial saliva medium with cysteine) on the microbial community of saliva-derived biofilm in vitro. 16S rRNA gene sequencing technology was used to analyze the microbial community of saliva-derived biofilm cultured for 72 h anaerobically. The metagenomes of biofilms were predicted from the clusters of orthologous groups. No significant difference was found between the saliva-derived biofilms grown on HA and glass in ACE, Chao, Shannon and Simpson indices. The abundances of only a few bacteria on HA were significantly different from those on glass with a low relative abundance (<0.5%). Compared with the biofilms developed in a modified artificial saliva medium with cysteine, biofilms in SHI medium were significantly higher (P < 0.05) in diversity. Linear discriminant analysis coupled with effect size measurement showed that some obligate anaerobic genera (Lactobacillus, Veillonella, Porphyromonas and Leptotrichia) were more abundant in SHI medium biofilms. The biofilms grown in different media were also significantly different in predicted gene categories. In conclusion, the growth media, not the substrates, have significant effects on the microbial community of saliva-derived biofilm in vitro.