title: An in vitro study on the effect of free amino acids alone or in combination with nisin on biofilms as well as on planktonic bacteria of Streptococcus mutans.
abstract: Free D-amino acids (D-AAs) are one of the most striking features of the peptidoglycan composition in bacteria and play a key role in regulating and disassembling bacterial biofilms. Previous studies have indicated that the antimicrobial peptide nisin can inhibit the growth of the cariogenic bacteria Streptococcus mutans. The present study investigated the effect of free amino acids either alone or in combination with nisin on biofilm and on planktonic S. mutans bacteria. The results of the MIC and MBC analyses showed that D-cysteine (Cys), D- or L-aspartic acid (Asp), and D- or L-glutamic acid (Glu) significantly improve the antibacterial activity of nisin against S. mutans and that the mixture of D-Cys, D-Asp, and D-Glu (3D-AAs) and the mixture of L-Cys, L-Asp, and L-Glu (3L-AAs) at a concentration of 40 mM can prevent S. mutans growth. Crystal violet staining showed that the D- or L-enantiomers of Cys, Asp, and Glu at a concentration of 40 mM can inhibit the formation of S. mutans biofilms, and their mixture generated a stronger inhibition than the components alone. Furthermore, the mixture of the three D-AAs or L-AAs may improve the antibacterial activity of nisin against S. mutans biofilms. This study underscores the potential of free amino acids for the enhancement of the antibacterial activity of nisin and the inhibition of the cariogenic bacteria S. mutans and biofilms.
authors.affiliation: Department of Operative Dentistry and Endodontics, Guanghua School of Stomatology, Sun Yat-sen University, Guangzhou, Guangdong, China; Guangdong Provincial Key Laboratory of Stomatology, Sun Yat-sen University, Guangzhou, Guangdong, China.
authors.forename: Zhongchun
authors.initials: Z
authors.lastname: Tong
authors.affiliation: Department of Operative Dentistry and Endodontics, Guanghua School of Stomatology, Sun Yat-sen University, Guangzhou, Guangdong, China.
authors.forename: Luodan
authors.initials: L
authors.lastname: Zhang
authors.affiliation: Department of Operative Dentistry and Endodontics, Guanghua School of Stomatology, Sun Yat-sen University, Guangzhou, Guangdong, China; Guangdong Provincial Key Laboratory of Stomatology, Sun Yat-sen University, Guangzhou, Guangdong, China.
authors.forename: Junqi
authors.initials: J
authors.lastname: Ling
authors.affiliation: Guangdong Provincial Key Laboratory of Stomatology, Sun Yat-sen University, Guangzhou, Guangdong, China.
authors.forename: Yutao
authors.initials: Y
authors.lastname: Jian
authors.affiliation: Department of Operative Dentistry and Endodontics, Guanghua School of Stomatology, Sun Yat-sen University, Guangzhou, Guangdong, China.
authors.forename: Lijia
authors.initials: L
authors.lastname: Huang
authors.affiliation: Department of Cariology Endodontology Pedodontology, Academic Centre for Dentistry Amsterdam (ACTA), Universiteit van Amsterdam and Vrije Universiteit, Amsterdam, The Netherlands.
authors.forename: Dongmei
authors.initials: D
authors.lastname: Deng
mesh_terms: D000596:Amino Acids / Q000494:pharmacology*; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D018441:Biofilms / Q000187:drug effects*; D004357:Drug Synergism; D008826:Microbial Sensitivity Tests; D050296:Microbial Viability / Q000187:drug effects; D009561:Nisin / Q000494:pharmacology*; D010933:Plankton / Q000187:drug effects / Q000254:growth & development; D013295:Streptococcus mutans / Q000187:drug effects* / Q000254:growth & development
chemical_list: D000596:Amino Acids; D000900:Anti-Bacterial Agents; D009561:Nisin