Treatment of Oral Biofilms by a D-Enantiomeric Peptide
Tian (Sally) Zhang
University Hill Secondary
Floor Location : S 040 H

Almost all dental diseases are caused by biofilms that consist of multispecies communities. DJK-5, which is a short D-enantiomeric, protease-resistant peptide with broad-spectrum anti-biofilm activity, was tested for its effect on oral multispecies biofilms. Peptide DJK-5 at 10 μg/mL effectively prevented the growth of these microbes in culture media in a time-dependent manner. In addition to the prevention of growth, peptide DJK-5 completely killed both Streptococcus mutans and Enterococcus faecalis suspended from biofilms after 30 minutes of incubation in liquid culture media. DJK-5 also led to the effective killing of microbes in plaque biofilm. The proportion of bacterial cells killed by 10 μg/mL of DJK-5 was similar after 1 and 3 days, both exceeding 85%. DJK-5 was able to significantly prevent biofilm formation over 3 days (P = 0.000). After 72 hours of exposure, DJK-5 significantly reduced and almost completely prevented plaque biofilm production by more than 90% of biovolume compared to untreated controls (P = 0.000). The proportion of dead biofilm bacteria at the 10 μg/mL DJK-5 concentration was similar for 1- and 3-day-old biofilms, whereby >86% of the bacteria were killed. DJK-5 was also able to kill >79% and >85% of bacteria, respectively, after one-time and three brief treatments of 3-day-old biofilms. The combination of DJK-5 and chlorhexidine showed the best bacterial killing among all treatments, with ~83% and >88% of bacterial cells killed after 1 and 3 minutes, respectively. No significant difference was found in the percentage of biofilm killing amongst three donor plaque samples after DJK-5 treatment. In particular, DJK-5 showed strong performance in inhibiting biofilm development and eradicating pre-formed oral biofilms compared to L-enantiomeric peptide 1018. DJK-5 was very effective against oral biofilms when used alone or combined with chlorhexidine. The Miseq sequencer generated a total of 24627828 raw sequences. After primer trimming and quality filtering 11868276 sequences remained. The most abundant phyla found in all samples were Firmiscutes, Bacteroidetes, Proterobacteria and Fusobacteria. In groups subjected to peptide treatment, there was a significant relative increase in the phyla Fusobacteria and Bacteroidetes and decrease in Firmicutes. In addition, there was reduced species richness in peptide treatment groups compared to control groups. This suggest the peptide can modulate the oral microbiome and indicates the therapeutic potential of DJK-5 to achieve a healthy oral microbioe. DJK-5 alone or combined with chlorhexidine may be a promising agent for use in oral anti-biofilm strategies in the future.