Nisin inhibits dental caries-associated microorganism in vitro

Nisin, produced by Lactococcus lactis, is an antibiotic peptide to effectively antagonize a broad spectrum of Gram-positive bacteria, and is widely used as a safe food antimicrobial agent. In the present study, we investigated whether nisin could be used as an effective antibiotic peptide against the nine common cariogenic microorganisms, and its antimicrobial activity could be affected by the ingredients of saliva in oral cavity. In the minimal inhibitory concentration (MIC) and minimal bactericide concentration (MBC) and spot-on-lawn assay, nisin displayed different MIC, MBC and antimicrobial activity against the nine tested strains. There was statistical difference between the inhibitory zone diameters of nisin against the different tested bacteria (p<0.05), but no statistical difference between the inhibitory zone diameters of nisin dissolved in PBS and saliva (p>0.05). Furthermore, morphology and membranes of Streptococcus sanguinis, Streptococcus mutans, Lactobacillus fermenti and Lactobacillus acidophilus with nisin treatment were observed and showed different degrees of variation by a Field Emission Scanning Electron Microscope (FE-SEM). Our findings suggested that nisin has considerable potential for prevention and treatment of dental caries.