鸡蛋清溶菌酶对头孢他啶诱导铜绿假单孢菌内毒素释放的抑制作用

目的研究鸡蛋清溶菌酶（lysozyme, LZM）对头孢他啶（ceftazidime, CFT）诱导的铜绿假单孢菌内毒素释放的影响。方法在肉汤或稀释血液培养的铜绿假单孢菌液中加入LZM、CFT或LZM/CFT，作用一定时间后，测定培养上清液中的内毒素浓度；将细菌培养上清液加入到巨噬细胞RAW 264.7中或注射入小鼠体内，测定其炎性因子(NO和TNF-α)诱生能力。结果在肉汤培养和血液培养中，CFT引起铜绿假单孢菌迅速溶解和释放大量内毒素到培养上清液中，其上清液在体外培养的巨噬细胞上和小鼠体内可诱导大量NO和TNF-α产生。而LZM与CFT联合使用能阻止细菌溶解，降低细菌内毒素释放，减少炎性因子NO和TNF-α的产生。结论LZM与CFT联合使用能抑制内毒素大量释放，减轻内毒素血症。

Inhibitory effect of egg white lysozyme on ceftazidime-induced release of endotoxin from Pseudomonas aeruginosa

AIM: To investigate the inhibitory effect of egg white lysozyme (LZM) on ceftazidime (CFT)-induced release of endotoxin from Pseudomonas aeruginosa. METHODS: P. aeruginosa PAO1 was inoculated in nutrition broth or diluted rabbit blood free of antibiotics in the presence or absence of LZM and incubated at 37 degrees C on a water bath shaker. beta-Lactam antibiotic, CFT, was added to cultures at 3.5 h (nutrition broth culture) or 5 h (diluted rabbit blood culture) after inoculation. After 3 h of CFT treatment, the supernatants from different bacterial cultures were prepared by centrifuge and the concentrations of endotoxin in the supernatants were measured. The bacterial supernatants were also added to a murine macrophage cell line RAW 264.7 or intravenously injected into carrageenin-sensitized mice. Tumor necrosis factor-alpha (TNF alpha) and nitric oxide (NO) concentrations in RAW 264.7 supernatants or in mouse sera were tested. RESULTS: CFT treatment alone obviously inhibited the growth of P. aeruginosa PAO1 accompanied by strong and rapid bacteriolysis and released relatively high concentration of endotoxin from bacteria both in nutrition broth and in diluted rabbit blood cultures. The bacterial supernatant from CFT treatment alone yielded high concentrations of TNF alpha both in RAW 264.7 cells and in mice and high level of NO in RAW 264.7 cells. Treatment with the combination of LZM and CFT evidently blocked the lysis of bacteria and reduced the release of endotoxin without decreasing bactericidal activity of CFT. TNF alpha and NO productivity of the supernatants prepared from the LZM/CFT combinative treated bacterial cultures were significantly decreased both in RAW 264.7 cells and in mice indicating that the inflammatory activity was reduced. CONCLUSION: LZM can effectively prevent CFT-induced bacteriolysis, endotoxin release and subsequent proinflammatory factor production but without decreasing bactericidal activity of CFT, resulting in the disassociation of bactericidal activity and bacteriolysis. Thus, LZM might be important for preventing endotoxemia in Gram-negative sepsis with the treatment of antibiotics.