Abstract
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, and may be a promising agent for use in oral anti-biofilm strategies in the future.
Highlights
Despite the best efforts of dental health professionals, oral infections are still widespread
In all instances DJK5 was superior to 1018 in its killing efficacy, which might have been due to its resistance to the proteolytic activity of plaque biofilm bacteria
There was no significant difference in the proportion of killed bacteria between 1, 2, and 3-day-old biofilms by each of the peptides and the proportion of bacteria killed by DJK-5 at 10 μg/mL (6.5 μM) at days 1 and 3 exceeded 85% (Fig 2C)
Summary
Despite the best efforts of dental health professionals, oral infections are still widespread. 85% of North American adults between the ages of 20 and 64 have dental restorations, and 23.7% of them have untreated dental caries [1]. Recent molecular methods have revealed that almost all dental diseases are caused by dental biofilms that consist of multispecies microbial communities [3,4,5,6]. Oral microbial biofilms are three-dimensionally structured communities embedded in an exopolysaccharide matrix [7,8,9,10] attached to solid surfaces such as tooth enamel, the surface of the root or dental implants [11], and they are extremely difficult to treat [10]. The most notable difference between oral bacteria in dental biofilms and the same strain grown planktonically is the increased tolerance/adaptive resistance of mature biofilm bacteria to antimicrobial agents. According to Sedlacek and Walker [12], the concentration of the antibiotic required to inhibit the growth of bacterial strains in biofilms is approximately 250 times greater than when the same strains are grown planktonically
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