title: [Synergistic effects of lysozyme with EDTA-2Na on antibacterial activity].
abstract: OBJECTIVE
  To evaluate the synergistic antibacterial effects of lysozyme with ethylenediaminetetraacetic acid disodium salt (EDTA-2Na) on Enterococcus faecalis (E. faecalis) and Porphyromonas endodontalis (P. endodontalis).
  
  
  METHODS
  E. faecalis and P. endodontalis were cultured and adjusted to 10(8) CFU/mL. Then 0.3, 0.5, 1, 2, 5, 10, 50, 100, 150 and 300 g/L of lysozyme were prepared with deionized water; and the lysozyme solutions were mixed with 0.5, 1.0, 2.0 g/L of EDTA-2Na, respectively. The bacteria and lysosome with/without EDTA-2Na interacted for 15 min, then water-soluble tetrazolium (WST) working solution was added and the activity of the bacteria was calculated by measuring optical densities at 450 nm and 630 nm with microplate spectrophotometer.
  
  
  RESULTS
  Regarding the pure lysozyme from 0.5 g/L to 150 g/L, more E. faecalis and P. endodontalis were inhibited when the concentration of lysozyme was higher, especially for E. faecalis. There was synergistic effect of lysozyme with EDTA-2Na on antibacterial activity, which was related to the concentration of lysozyme. On E. faecalis, the antibacterial activity of lysozyme with EDTA-2Na was 1.2-3.7 folds than the pure lysozyme when the concentration of lysozyme was 0.5-50 g/L (P<0.05), and on P. endodontalis, the antibacterial activity of lysozyme with EDTA-2Na was 1.3-3.5 folds than the pure lysozyme when the concentration of lysozyme was 0.5-10 g/L (P<0.05). When the concentration of lysozyme was higher than 100 g/L, EDTA-2Na did not show synergistic effect on the antibacterial activity (P>0.05).
  
  
  CONCLUSIONS
  For E. faecalis and P. endodontalis, a low concentration of lysozyme with EDTA-2Na showed significant synergistic antibacterial activity, while a high concentration of lysozyme with EDTA-2Na did not.
authors: Department of Cariology and Endodontology, Peking University School and Hospital of Stomatology, Beijing 100081, China.
authors: Xiao-man
authors: XM
authors: Li
authors: Department of Cariology and Endodontology, Peking University School and Hospital of Stomatology, Beijing 100081, China.
authors: Xiao-yan
authors: XY
authors: Wang
authors: Department of Cariology and Endodontology, Peking University School and Hospital of Stomatology, Beijing 100081, China.
authors: Xue-jun
authors: XJ
authors: Gao
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D004357:Drug Synergism; D004492:Edetic Acid / Q000494:pharmacology*; D013293:Enterococcus faecalis / Q000187:drug effects*; D008826:Microbial Sensitivity Tests; D009113:Muramidase / Q000494:pharmacology*; D045202:Porphyromonas endodontalis / Q000187:drug effects*
chemical_list: D000900:Anti-Bacterial Agents; D004492:Edetic Acid; D009113:Muramidase