| More attention has increasingly been paid to the antibacterial peptide dueto bacterial resistance to some common antibiotics. Nisin, a34-residue peptideproduced by Lactococcus lactis, is emerged as one of the most extensivelystudied lantibiotics and possess many excellent properties. However, to ourknowledge, it appears to be no report that nisin was used to inhibit pathogens inoral cavity. In the present study, the antibacterial peptide nisin is considered toinhibit pathogens in oral cavity.Firstly, the probiotic L. lactis was first used to inhibit the major cariogenicbacterium Streptococcus mutans. We found that L. lactis competitively inhibitedS. mutans growth under nutritional deficiency, and the metabolites of S. mutans,including several exogenous molecular signals, enhanced the expression ofgenes related to nisin synthesis in L. lactis. Additionally, L. lactis effectivelycolonized the surface of tooth enamel, which showed substantially less decaywith L. lactis adhesion compared to S. mutans adhesion. Secondly, in theminimal inhibitory concentration (MIC) and minimal bactericide concentration (MBC) and spot-on-lawn assay, nisin displayed different antimicrobial activityagainst the nine cariogenic bacteria. The antibacterial activity of nisin was notaffected by ingredient in saliva. Furthermore, morphology and membranes ofStreptococcus sanguinis, Streptococcus mutans, Lactobacillus fermenti andLactobacillus acidophilus with nisin treatment were observed and showeddifferent degrees of damage by a Field Emission Scanning Electron Microscope(FE-SEM). Thirdly, in an in vitro synergetic evaluation of nisin and sodiumfluoride or chlorhexidine against S mutans, a synergetic effect on S. mutans wasfound between nisin and sodium fluoride, but there was no interaction betweennisin and chlorhexidine by the checkerboard, the fractional inhibitoryconcentration (FIC) and the fractional bactericidal concentration (FBC) tests. S.mutans survival rates showed a significant decline after treatment with acombination of nisin and sodium fluoride in a time-kill study. FE-SEM showedthat the damage to S. mutans with the combined nisin and sodium fluoridetreatment was the most severe among all of the different single and combinedantimicrobial treatments. Furthermore, in the antibiofilm test, nisin incombination with sodium fluoride produced a stronger bactericidal effect on a S.mutans biofilm for4h and16h compared with sodium fluoride alone byconfocal laser scanning microscopy. The studies indicate that the probiotic Llactis and antibacterial peptide nisin have the potential to be new methods toinhibit cariogenic bacteria in oral cavity and prevent dental caries..MTAD (A mixture of tetracycline isomer, acid and detergent) is a higheffective intracanal irrigant. In the study of MTADN (nisin in combination withMTAD) against nisin common pathogens associated with dental pulp and rootcanal infection, MTADN showed a strong and rapid antibacterial activity. In thestudy of inhibtion of E. faecalis associated with the secondary and persistent root canal infection, the synergetic action between nisin and a commonintracanal irrigant, MTAD was evaluated by checkerboard and FIC, and theresult showed that nisin can markedly improve the bactericidal effect of MTADon E. faecalis. The MBC of MTADN against E. faecalis was lower than that ofMTAD and MTAN (substitution of doxycycline in MTAD with nisin). Whendoxycycline is applied in combination with nisin, the pores formed by nisin onthe surface of the cell membrane can facilitate the penetration of doxycyclinemolecules into the microorganism and exert its antibacterial role, and therebythe combination of nisin and doxycycline had a significantly synergeticantibacterial effect on E. faecalis. The morphological modification of FE-SEMalso showed that the most damage on E. faecalis was found with the treatmentof MTADN. The studies indicate that the drugs combination between nisin andMTAD has the potential to be as an effective intracanal irrigant. |
PDF Full Text Request