小剂量脂多糖预处理对切口耐药菌感染的防治作用

Lipopolysaccharide preconditioning prevents incision infection induced by drug-resistant bacteria in mice

目的：探讨小剂量脂多糖预处理对切口耐药菌感染的影响。方法制备浓度为1．8＆#215;109 CFU／mL的耐甲氧西林金黄色葡萄球菌（ MRSA）菌液。取60只BALB／c小鼠，随机分为5组，每组12只，雌雄各半。组1～组3采用滴入加涂擦法用1、0．5、0．25 mL MRSA菌液量制作切口感染模型，组4和组5分别为切口组和空白对照。观察制模后4 d切口状况。取112只BALB／c小鼠，随机平均分为7组，每组16只，雌雄各半，A组为0．25 mg＆#183; kg－1＆#183;次－1脂多糖预处理组，B组为0．5 mg＆#183; kg－1＆#183;次－1脂多糖预处理组， C 组为1 mg ＆#183; kg－1＆#183;次－1脂多糖预处理组， D 组为1．5 mg＆#183; kg－1＆#183;次－1脂多糖预处理组，E组为无菌等渗氯化钠溶液预处理组，F组为切口感染组，G组为空白对照组。于制作切口感染模型前48 h和24 h腹腔注射脂多糖。观察制模后小鼠1至7 d每天的体温变化、第3天及第7天血常规、第7天血清细胞因子的变化情况。制模后第7天处死小鼠，取切口周围软组织做HE染色，镜下观察。采用重复测量数据方差分析和多因素方差分析进行数据统计。结果切口MRSA感染模型显示，0．5 mL菌液切口感染组有6只小鼠切口红肿，6只化脓，制作的切口感染模型较为稳定，并以此菌液量制作脂多糖预处理组的切口感染模型。采用脂多糖预处理后，B组小鼠体温变化幅度最小，第3天和第7天时白细胞和淋巴细胞升高幅度最低，且第7天时粒细胞恢复至正常水平。制模后第7天，B组血清白细胞介素（ IL）-1β、IL-6、肿瘤坏死因子（ TNF）-α升高幅度最小，IL-10升高幅度最大。 B组小鼠的切口化脓率为25．00％（4／16），明显低于D、E、F组的化脓率（χ2＝7．988、19．940和19．940，P＜0．01）。结论小剂量脂多糖预处理可以降低机体及切口局部的感染严重程度，其中0．5 mg＆#183; kg－1＆#183;次－1为最佳预处理剂量。

Objective To investigate the effect of low dose lipopolysaccharide （ LPS ） preconditioning on prevention of incision infection by drug-resistant bacteria.Methods Methicillin-resistant Staphylococcus aureus （ MRSA） suspension with concentration of 1.8 ＆#215;109 CFU/mL was prepared.Sixty BALB/c mice were randomly divided into five groups （12 in each group, half male and half female）.A medical longitudinal incision of the right thigh was made in mice in group 1-4, and 1, 0.5, 0.25 and 0 mL bacteria suspension was dropped on the surface of the incision and the incision was observed 4d after the model established.Group 5 was the blank control.Then 112 BALB/c mice were randomly divided into 7 groups （ each group had sixteen mice, half male and half female ）： group A （ preconditioned with LPS 0.25 mg＆#183; kg-1＆#183; time-1）, group B （ preconditioned with LPS 0.5 mg ＆#183; kg-1 ＆#183; time-1 ）, group C （preconditioned with LPS 1 mg＆#183; kg-1 ＆#183; time-1 ）, group D （preconditioned with LPS 1.5 mg＆#183; kg-1 ＆#183; time-1 ） , group E （ preconditioned with sterile normal saline） , group F （ incision infected） , and group G＆amp;nbsp;（ blank control） .LPS was given by intraperitoneal injection 48 h and 24 h before the establishing of the infection model.Body temperature was monitored every day after the model established, blood routine examination was performed on d3 and d7, and serum cytokines was detected on d7.All the mice were sacrificed on d7, and soft tissues around the incision were taken for hematoxylin-eosin staining.Repeated measures ANOVA and univariate ANOVA were performed for data analysis. Results Redness and suppuration were observed in 6 mice infected with 0.5 mL bacteria suspension, respectively, then 0.5 mL bacteria suspension was used for LPS preconditioning experiments.With LPS preconditioning, the body temperatures of mice in group B were with relatively minor changes, and the rises of white blood cells and lymphocytes on d3 and d7 were relatively modest.Granulocytes in group B returned to the normal level on d7.Besides, the rises of interleukin （IL）-1β, IL-6, and tumor necrosis factor （TNF）-αin group B were also less, while IL-10 was increased greatly.Suppuration was observed in 4 mice in group B （ 4/16, 25.00%）, and the rate was lower than group D, E and F （χ2 =7.988, 19.940 and 19.940,P〈0.01）. Conclusion LPS （0.5 mg＆#183; kg-1 ＆#183; time-1 ） preconditioning can reduce the severity of incision infection caused by MRSA in mice.