Effects of antimicrobial peptide GH12 on the morphology and composition of cariogenic three-species biofilm

Objective: To evaluate the effects of antimicrobial peptide GH12 designed de novo on the structure, morphology, and composition of a cariogenic three-species biofilm.

Methods: The cariogenic three-species biofilm consis-ted of the cariogenic Streptococcus mutans (S. mutans) and commensal bacteria Streptococcus sanguinis (S. sanguinis) and Streptococcus gordonii (S. gordonii). The biofilm was treated using GH12 (2, 4, and 8 mg·L-1), and untreated biofilm was used as the control. Changes in the morphology and structure of the three-species biofilm were evaluated through crystal violet staining, scanning electron microscopy (SEM), and fluorescent in situ hybridization (FISH). Moreover, S. mutans in the biofilm was selectively cultured, and its colony-forming units were counted.

Results: The biomass and density of the cariogenic three-species biofilm treated with GH12 decreased compared with those of the control. The number of S. mutans decreased gradually and eventually became undetectable, whereas the number of S. gordonii and S. sanguinis increased and became predominant in the biofilm.

Conclusions: GH12 can reduce the number of S. mutans within the cariogenic three-species biofilm, destroys its integrity, and consequently makes the biofilm easy to remove.