Antimicrobial Effect of a Peptide Containing Novel Oral Spray on Streptococcus mutans

Abstract

Objective: To investigate the antibacterial effect of a novel antimicrobial peptide containing oral spray GERM CLEAN on Streptococcus mutans (S. mutans) in vitro and further explore the related mechanisms at phenotypic and transcriptional levels.

Methods: The disk diffusion method was used to preliminarily appraise the antimicrobial effect of GERM CLEAN. The minimal inhibitory concentration (MIC) of GREM CLEAN towards S. mutans was determined by the broth dilution method. S. mutans was determined by the broth dilution method.

Results: The diameter (10.18 ± 1.744 mm) of inhibition zones formed by GERM CLEAN preliminarily indicated its inhibitory effect on the major cariogenic bacteria S. mutans was determined by the broth dilution method. S. mutans was determined by the broth dilution method. S. mutans was determined by the broth dilution method. S. mutans was determined by the broth dilution method. gtfB, gtfC, gtfD, and ldh were significantly repressed by treating with GERM CLEAN, and this was consistent with our phenotypic results.

Conclusion: The novel antimicrobial peptide containing oral spray GERM CLEAN has an anti-Streptococcus mutans effect and the inhibitory property may be due to suppression of the virulence factors of S. mutans including adhesive, acidogenicity, EPS, and biofilm formation.Streptococcus mutans effect and the inhibitory property may be due to suppression of the virulence factors of S. mutans including adhesive, acidogenicity, EPS, and biofilm formation.S. mutans was determined by the broth dilution method.

Figure 1

Effect of GERM CLEAN at 1/2MIC on the growth curve of S. mutans.

Figure 2

The anti-adherence effect of 1/2MIC GERM CLEAN on S. mutans. (a) The OD_600nm of adherent bacteria treated with 1/2MIC level of GERM CLEAN or BHIS control; (b) the antiadherence percentage of the initial adherence stage (1 h, 2 h, and 4 h) calculated by (OD600 nm of control group − OD_600nm of assay group)/OD600 nm of control group. ^∗p < 0.05.

Figure 3

Effect of 1/2MIC GERM CLEAN on biofilm formation and water-insoluble EPS of S. mutans. (a) Quantitative data of the biofilm formation measured by crystal violet dye; (b) the water-insoluble EPS measured by the anthrone method. ^∗p < 0.05.

Figure 4

Scanning electron microscopy observation of S. mutans biofilm formed after 24 h of incubation. (a) and (c) were taken from the untreated control group, while (b) and (d) represented the group treated with 1/2 MIC concentration of GERM CLEAN. (a) and (b) 5000x; (c) and (d) partially magnified (20000x) from the red circles in (a) and (b), respectively.

Figure 5

CLSM images of S. mutans biofilm formed in the presence and absence of the sub-MIC (1/2MIC) level of GERM CLEAN after 24 h of incubation. (a), (b), and (c) were from the treated group; (d), (e), and (f) were from the control group; (a) and (d) show the whole biofilm images; live bacteria, stained green (b, e); dead cells, stained red (c, f).

Figure 6

Effect of 1/2MIC concentration of GERM CLEAN on S. mutans acid production measured by glycolytic pH drop assay. The horizontal dotted line represents the critical pH value (pH 5.5) to S. mutans.

Figure 7

Expression of various virulence genes of S. mutans in response to the treatment with GERM CLEAN. Gene expression was quantified by real-time PCR, with gyrA rRNA as an internal control. ^∗p < 0.05.