抗生素诱导革兰阴性杆菌释放内毒素的实验研究(一)

目的研究抗生素诱导革兰阴性细菌释放内毒素的规律、特点和可能机制，为临床上合理应用抗生素提供实验依据。方法选择目前临床上G-细菌感染中最常见的绿脓杆菌和大肠杆菌，以及治疗中最常用的4种代表性抗生素亚胺培南(IMP)、头孢他啶(CTZ)、培福新(PFX)和丁胺卡那霉素(AMN)作为观察对象。4种抗生素以0.5、1、5和10MIC浓度分别作用于两种细菌后，观察各时相点细菌菌量、细菌形态学变化，检测培养液上清中游离内毒素水平。结果IMP、CTZ、AMN和PFX四者间的杀菌曲线无明显差异，但能导致细菌产生不同的形态学改变。IMP导致细菌产生球状变，CTZ和PFX引起细菌丝状变，AMN则导致细菌菌体溶解。同等条件下不同种类抗生素诱导细菌释放内毒素的能力为CTZ＞PFX＞IMP＞AMN；不同抗生素浓度诱导细菌释放内毒素的能力为0.5MIC＞1MIC＞5MIC＞10MIC；不同抗生素作用时间诱导细菌释放内毒素的水平为8h＞6h＞4h＞2h；不同菌种释放内毒素的能力为绿脓杆菌＞大肠杆菌。结论IMP、CTZ、AMN和PFX4种抗生素作用于绿脓杆菌和大肠杆菌后，均能诱导细菌释放不同水平的内毒素，这种释放与细菌形态学改变有关，亦受抗生素种类、浓度、作用时间以及不同菌种的影响。建议临床选用低诱导力的敏感抗生素(如IMP)，减少细菌释放内毒素的可能性。

An experimental study on the release of endotoxin from gram negative bacteria induced by antibiotics

Objective To explore the characteristics and possible mechanism of LPS released from Gram negative bacteria induced by antibiotics,so as to improve clinical management of endotoxemia and sepsis. Methods Cultures containing PA103 subtype of Pseudomonas aeruginosa(PA) and E coli 25922 subtype of E coli were treated with four kinds of antibiotics as Imipenam(IMP),ceftazidime(CTZ),amikacin (AMN) and pefloxacine (PFX) in four concentrations of 0.5,1,5 and 10 MIC for 8 hours.The changes in the bacterial quantity and morphology and the supernatant levels of free LPS of the culture media were observed at different time points. Results All the four kinds of antibiotics could kill the tested bacteria in similar degree,but lead to the different types of morphological changes of the bacteria.In detail,IMP could convert the bacteria into spherical shape,while CTZ and PFX made the bacteria to filamentous shape.But AMN could induce lysis of bacterial thallus.Under same condition,the ability of different kinds and concentrations of antibiotics to induce LPS release ranked as CTZ>PFX>IMP>AMN,0.5MIC>1MIC>5MIC>10MIC.Along with the prolongation of the action time,the LPS release increased.Furthermore,PA103 released less endotoxin than E.coli after the action of antibiotics. Conclusion All of the four antibiotics,i,e,IMP,CTZ,AMN and PFX could induce PA103 and E coli 25922 to release different levels of LPS,which was related to bacterial morphological changes.The LPS release from the bacteria was correlated to the antibiotics applied,concentrations,action time and the bacterial features.Antibiotics with less ability of inducing LPS release were recommended for clinical management of the sepsis and/or septic shock caused by Gram negative bacteria.