Effects of Antimicrobial Peptide GH12 on the Cariogenic Properties and Composition of a Cariogenic Multispecies Biofilm

Abstract

Dental caries is a biofilm-mediated disease that occurs when acidogenic/aciduric bacteria obtain an ecological advantage over commensal species. In previous studies, the effects of the antimicrobial peptide GH12 on planktonic bacteria and monospecies biofilms were confirmed. The objectives of this study were to investigate the effects of GH12 on a cariogenic multispecies biofilm and to preliminarily explain the mechanism. In this biofilm model, Streptococcus mutans ATCC 70061 was the representative of cariogenic bacteria, while Streptococcus gordonii ATCC 35105 and Streptococcus sanguinis JCM 5708 were selected as healthy microbiota. The results showed that GH12 was more effective in suppressing S. mutans than the other two species, with lower MIC and minimal bactericidal concentration (MBC) values among diverse type strains and clinical isolated strains. Therefore, GH12, at no more than 8 mg/liter, was used to selectively suppress S. mutans in the multispecies biofilm. GH12 at 4 mg/liter and 8 mg/liter reduced the cariogenic properties of the multispecies biofilm in biofilm formation, glucan synthesis, and lactic acid production. In addition, GH12 suppressed S. mutans within the multispecies biofilm and changed the bacterial composition. Furthermore, 8 mg/liter GH12 showed a selective bactericidal impact on S. mutans, and GH12 promoted hydrogen peroxide production in S. sanguinis and S. gordonii, which improved their ecological advantages. In conclusion, GH12 inhibited the cariogenic properties and changed the composition of the multispecies biofilm through a two-part mechanism by which GH12 directly suppressed the growth of S. mutans as well as enhanced the ecological competitiveness of S. sanguinis and S. gordonii. IMPORTANCE Dental caries is one of the most prevalent chronic infectious diseases worldwide, with substantial economic and quality-of-life impacts. Streptococcus mutans has been considered the principal pathogen of dental caries. To combat dental caries, an antimicrobial peptide, GH12, was designed, and its antibacterial effects on planktonic S. mutans and the monospecies biofilm were confirmed. As etiological concepts of dental caries evolved to include microecosystems, the homeostasis between pathogenic and commensal bacteria and a selective action on cariogenic virulence have increasingly become the focus. The novelty of this research was to study the effects of the antimicrobial peptides on a controlled cariogenic multispecies biofilm model. Notably, the role of an antimicrobial agent in regulating interspecific competition and composition shifts within this multispecies biofilm was investigated. With promising antibacterial and antibiofilm properties, the use of GH12 might be of importance in preventing and controlling caries and other dental infections.

Peptide Mediated Antimicrobial Dental Adhesive System

“…In agreement with previous studies, GH12 exhibits αhelix conformations in solvents mimicking interactions at the membranes [76]. Our results are in agreement with the trends that are shared by the modified GH12 and GH12-M2.…”

“…We further explored the likely residues involved in forming helical secondary structure through computational structure flexibility. The α-helix secondary structure of GH12 is a design target for functional integration of the peptide to the adhesive system [76]. The presence of α-helix conformation was confirmed through our vibrational spectroscopy measurements for peptides including the modified GH12.…”

“…The α -helix secondary structure of GH12 is a design target for functional integration of the peptide to the adhesive system [ 76 ]. The presence of α -helix conformation was confirmed through our vibrational spectroscopy measurements for peptides including the modified GH12.…”

Peptide and non‐peptide mimetics as potential therapeutics targeting oral bacteria and oral biofilms

“…Even at a sub‐inhibitory dose of 0.5 × MIC, GH12 inhibited acid production, EPS synthesis and biofilm formation of S. mutans and significantly down‐regulated the expression of virulence genes including ldh, gtfBCD, vicR, liaR and comDE (Wang, Wang, et al, ). Subsequently, Jiang et al () showed that treatment of a three species biofilm comprising S. mutans, S. gordonii and S. sanguinis with 8 µg/ml GH12 reduced the abundance of S. mutans and reduced the level of water‐insoluble glucan (Jiang et al, ). Interestingly, as the abundance of S. mutans decreased in the treated biofilms, the level of S. gordonii increased and became the dominant organism in the biofilm by 48 hr.…”

Antimicrobial peptide GH12 as root canal irrigant inhibits biofilm and virulence of Enterococcus faecalis

“…The good biocompatibility of GH12 in vivo was further confirmed in a rat model (Wang et al 2019). Furthermore, GH12 was reported to have excellent antimicrobial properties against dental cariogenic bacteria and biofilms in vitro , especially for Gram‐positive bacteria (Tu et al 2016, Wang et al 2017, Jiang et al 2018). GH12 has been reported to have rapid and efficient bactericidal activity against oral Streptococci , Lactobacilli and Actinomyces species with low concentrations (8.0–64.0 mg L −1 ) (Tu et al 2016).…”