溶菌酶与EDTA二钠的协同抑菌作用

目的：研究溶菌酶与乙二胺四乙酸二钠（ethylenediaminetetraacetic acid disodium salt，EDTA二钠）对粪肠球菌和牙髓卟啉单胞菌的协同抑菌作用。方法：分别培养粪肠球菌和牙髓卟啉单胞菌，并调整菌液浓度至108菌落形成单位（colony-forming unit，CFU）/mL；配制终浓度为0.3、0.5、1、2、5、10、50、100、150和300 g/L的单纯溶菌酶抑菌液，以及添加浓度为0.5、1.0、2.0 g/L的EDTA二钠的混合抑菌液。将菌液与抑菌液作用15 min，加入水溶性四唑盐（water-soluble tetrazolium，WST）工作液染色，酶标仪测定光密度值，计算细菌活性。结果：单纯溶菌酶抑菌液（浓度0.5~150 g/L）对两种细菌的抑菌作用随溶菌酶浓度的升高而增强，且对粪肠球菌的抑菌作用更显著。EDTA二钠与溶菌酶有协同抑菌作用，与溶菌酶浓度相关。溶菌酶浓度为0.5~50 g/L时，EDTA二钠协同溶菌酶作用于粪肠球菌（P<0.05），可使其抑菌作用提高约1.2~3.7倍；溶菌酶浓度为0.5~10 g/L时， EDTA二钠协同溶菌酶作用于牙髓卟啉单胞菌（P<0.05），可使其抑菌作用提高约1.3~3.5倍；当溶菌酶浓度大于100 g/L时，加入EDTA二钠对细菌均没有明显的协同抑菌作用（P>0.05）。结论：对于粪肠球菌及牙髓卟啉单胞菌，在溶菌酶较低浓度时，EDTA二钠有协同抑菌作用；在溶菌酶较高浓度时，EDTA二钠无协同抑菌作用。

Synergistic effects of lysozyme with EDTA-2Na on antibacterial activity

Objective:To evaluate the synergistic antibacterial effects of lysozyme with ethylenediami-netetraacetic 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 108 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, re-spectively.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 mea-suring 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.fae-calis, 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 antibac-terial 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). Conclusion: 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-2 Na did not .