Study on the effect of L-arginine on Streptococcus mutans and Streptococcus gordonii in vitro

ZHANG Wen; HUANG Xin-yi; GENG Xiao-xi; LI Meng-ya; LUO Jun-jiao; XU Qing-an

doi:10.19538/j.kq.2025.01.010

Abstract：Objective To study the effect of L-arginine on Streptococcus mutans(S.mutans)and Streptococcus gordo-nii(S.gordonii)in vitro.Methods The study was conducted from June 2022 to November 2023 at the Public Laboratory Platform,Department of Medicine,Jianghan University.Bacteria were categorized into S.mutans group,S.gordonii group,and S.mutans & S.gordonii group based on individual or mixed cultures.After treatment with different mass fractions(2.00％,1.00％,0.10％)of L-arginine,the optical density values at wavelength 620 nm(OD620)after 24 h,48 h and 96 h of bacterial culture in S.mutans and S.gordonii groups,as well as the relative expression levels of bacteria and S.mu-tant related genes(gtfB,SMU.150,nlmD)in S.mutans & S.gordonii group were detected,and compared with the blank control(no L-arginine treatment)with the same cul-ture time.Scanning electron microscopy was used to ob-serve the effects of different mass fractions(2.00％,1.00％,0.10％)of L-arginine on the process of plaque biofilm forma-tion and the formed plaque biofilm of S.mutans group,S.gordonii group and S.mutans & S.gordonii group.Results In S.mutans and S.gordonii groups,the OD620 values of the 2.00％and 1.00％L-arginine-treated bacterial fluids decreased significantly after 24 h of culture compared with those of the blank control fluids at the same culture time,and the differ-ences were statistically significant(all P＜0.05),whereas the OD620 values of the bacterial fluids treated with 0.10％L-arginine after 24 h,48 h and 96 h of culture were compared with the blank control bacterial fluids at the same culture time,and the differences were not statistically significant(all P＞0.05).In S.mutans & S.gordonii group,the relative ex-pression of S.mutans and S.gordonii was significantly reduced after 24 h of culture after being treated with 2.00％and 1.00％L-arginine,and the relative expression of S.mutant was significantly reduced while that of S.gordonii was signifi-cantly increased at 24 h after being treated with 0.10％L-arginine.The relative expression of gtfB,nlmD and SMU.150 was significantly reduced after 24 h of L-arginine treatment for all mass fractions,and the differences were all statistical-ly significant(all P＜0.05).Scanning electron microscopy showed that the plaque biofilms of S.mutans,S.gordonii and S.mutans & S.gordonii groups became loose after 24 h of culture after being treated with 2.00％and 1.00％L-arginine,while after treatment with 0.10％L-arginine,the plaque biofilms of S.gordonii and S.mutans & S.gordonii groups showed no significant change,but the growth of plaque biofilms of the S.mutans group was inhibited.Conclusion The 2.00％L-arginine and 1.00％L-arginine have inhibitory effects on both S.mutans and S.gordonii;0.10％L-arginine can inhibit the growth of S.mutant plaque biofilm and increase the relative content of S.gordonii in mixed plaque biofilm.L-arginine can help to construct a healthy oral plaque microecology,which provides a new direction for the prevention of caries.