title: Human cathelicidin LL-37 enhance the antibiofilm effect of EGCG on Streptococcus mutans.
abstract: Streptococcus mutans forms biofilms as a resistance mechanism against antimicrobial agents in the human oral cavity. We recently showed that human cathelicidin LL-37 exhibits inhibitory effects on biofilm formation of S. mutans through interaction with lipoteichoic acid (LTA), but without antibacterial or biofilm dispersal abilities. (-)-Epigallocatechin gallate (EGCG) is the most abundant constituent of tea catechins that has the greatest anti-infective potential to inhibit the growth of various microorganisms and biofilm formation. Therefore, in this study, we evaluated whether LL-37 interacts with EGCG to enhance the antibiofilm effect of EGCG on S. mutans biofilm formation.
  
  
  
  Clinical S. mutans strains (n = 10) isolated from children's saliva were tested in a biofilm formation assay. The antibiofilm effect of EGCG with and without LL-37 was analyzed by the minimum biofilm eradication concentration assay and confirmed using field emission-scanning electron microscopy. In addition, the interaction among EGCG, LL-37, and LTA of S. mutans was determined using quartz crystal microbalance analysis.
  
  
  
  EGCG killed 100 % of planktonic S. mutans within 5 h, inhibited biofilm formation within 24 h, and reduced bacteria cells in preformed biofilms within 3 h at a concentration of 0.2 mg/mL. However, EGCG did not appear to interact with LTA. LL-37 effectively enhanced the bactericidal activity of EGCG against biofilm formation and preformed biofilms as determined by quantitative crystal violet staining and field emission-scanning electron microscopy. In addition, quartz crystal microbalance analysis revealed that LL-37 interacted with EGCG and promoted binding between EGCG and LTA of S. mutans.
  
  
  
  We show that LL-37 enhances the antibiofilm effect of EGCG on S. mutans. This finding provides new knowledge for dental treatment by using LL-37 as a potential antibiofilm compound.
authors.affiliation: Department of Pathogenic Microbiology and Immunology, School of Basic Medical Sciences, Xi'an Jiaotong University, Yanta West Road No.76, Xi'an, 710061, ShaanXi, China. yijie_guo@mail.xjtu.edu.cn.|Key Laboratory of Environment and Genes Related to Diseases, Ministry of Education of China, Xi'an Jiaotong University, Yanta West Road No.76, Xi'an, 710061, ShaanXi, China. yijie_guo@mail.xjtu.edu.cn.
authors.forename: Yi-Jie
authors.initials: YJ
authors.lastname: Guo
authors.affiliation: Department of Pathogenic Microbiology and Immunology, School of Basic Medical Sciences, Xi'an Jiaotong University, Yanta West Road No.76, Xi'an, 710061, ShaanXi, China.|Clinical Laboratory, AnKang City Central Hospital, Jinzhou South Road No.85, AnKang, 725000, ShaanXi, China.
authors.forename: Bo
authors.initials: B
authors.lastname: Zhang
authors.affiliation: Department of Pathogenic Microbiology and Immunology, School of Basic Medical Sciences, Xi'an Jiaotong University, Yanta West Road No.76, Xi'an, 710061, ShaanXi, China.|Key Laboratory of Environment and Genes Related to Diseases, Ministry of Education of China, Xi'an Jiaotong University, Yanta West Road No.76, Xi'an, 710061, ShaanXi, China.
authors.forename: Xue-Song
authors.initials: XS
authors.lastname: Feng
authors.affiliation: Department of Pathogenic Microbiology and Immunology, School of Basic Medical Sciences, Xi'an Jiaotong University, Yanta West Road No.76, Xi'an, 710061, ShaanXi, China.|Key Laboratory of Environment and Genes Related to Diseases, Ministry of Education of China, Xi'an Jiaotong University, Yanta West Road No.76, Xi'an, 710061, ShaanXi, China.
authors.forename: Hui-Xun
authors.initials: HX
authors.lastname: Ren
authors.affiliation: Department of Pathogenic Microbiology and Immunology, School of Basic Medical Sciences, Xi'an Jiaotong University, Yanta West Road No.76, Xi'an, 710061, ShaanXi, China. xujiru@mail.xjtu.edu.cn.|Key Laboratory of Environment and Genes Related to Diseases, Ministry of Education of China, Xi'an Jiaotong University, Yanta West Road No.76, Xi'an, 710061, ShaanXi, China. xujiru@mail.xjtu.edu.cn.
authors.forename: Ji-Ru
authors.initials: JR
authors.lastname: Xu
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D023181:Antimicrobial Cationic Peptides / Q000494:pharmacology*; D018441:Biofilms / Q000187:drug effects*; D002392:Catechin / Q000031:analogs & derivatives / Q000494:pharmacology; D006801:Humans; D008826:Microbial Sensitivity Tests; D013295:Streptococcus mutans; D054804:Cathelicidins
chemical_list: D000900:Anti-Bacterial Agents; D023181:Antimicrobial Cationic Peptides; D002392:Catechin; C045651:epigallocatechin gallate; D054804:Cathelicidins
keywords: Biofilm; EGCG; LL-37; Streptococcus mutans