新生乳鼠早期肠道细菌移位与影响因素研究

Time course of spontaneous bacterial translocation from gastrointestinal tract and its influential factors among neonatal rats

目的观察新生鼠早期细菌移位的发生过程,探讨细菌移位、肠道菌群和免疫功能的关系,并阐明其临床意义。方法将120只SD乳鼠随机分为两组:A组100只,分别于生后即刻、第3天、第7天、第14天、第30天各处死20只;B组20只,于生后每日腹腔注射青霉素钾并于第7天处死,做相应指标检测。采用需氧菌、厌氧菌培养技术,根据形态学、常规生化反应、API系统、代谢终产物色谱分析等对所培养细菌进行鉴定计数,动态观察乳鼠生后0～30 d肠道菌群定植和细菌移位的发生过程;采用流式细胞仪测定新生大鼠脾脏中CD3和CD25淋巴细胞数量。结果新生鼠早期肠道菌群定植表现为需氧菌定植在先,厌氧菌定植在后,后者增长迅速,很快超过前者成为肠道优势菌。肠系膜淋巴结的细菌移位与CD25/CD3呈正相关(P<0.05)。结论新生鼠早期细菌移位现象普遍存在并呈"一过性,"肠道厌氧菌数量和机体免疫功能在细菌移位发生过程中发挥重要作用。应用抗生素可影响肠道菌群定植和菌群结构,加重细菌移位程度,是引发机体内源性感染的潜在因素。[临床儿科杂志,2007,25(12):1025-1029]

Objectives To study colonization of intestinal normal flora and spontaneous bacterial translocation, investigate the relationship between bacterial colonization of gastrointestinal tract and the function of immune system and study the effects of antibiotics on bacterial colonization in newborn rats. Methods One hundred and twenty SD rats were randomly selected in this study. Among them, 100 rats were sacrificed by cervical dislocation on 0,3,7,14 and 30 days after delivery. The remaining 20 rats received antibiotics intra-abdominally right after delivery for 7 days. The mesenteric lymph node （MLN） complex,spleen,liver and terminal ileal loop were excised and studied. Samples of these tissues were inoculated on four different plates for aerobic and anaerobic bacteria culture. Bacteria were identified and quantitated with morphological studies,routine biochemical analysis,API system,chromatogram analysis of the terminal metabolic products of the bacteria. Dynamic changes of colonization and translocation of the bacteria in the intestine of young mice aged 0-30 days were observed. Each rat＇s spleen was sampled and made into mononuclear cell supernatant. Amount of CD3 and CD25 cells were quantified with flow cytometry. Results （1）Colonization of aerobic flora preceded anaerobic flora in the rat,while the latter rapidly increased in number until becoming the predominant bacteria. （2） Translocation of the bacteria occurred in the early neonatal period and the number decreased quickly,having close relationship with the host＇s immune function. （3）The number of colonization and the constitution of the bacteria were affected by the use of antibiotics. Increased number of translocation was the potential risk factor for endogenous infection. Conclusions Spontaneous bacteria translocation is a common phenomenon in neonatal rats. Intestinal normal flora is protective against bacteria translocation. Anaerobic bacteria may play the most important role. Spontaneous bacteria translocation in neonatal period can stimulate the immune system. Antibiotics have some adverse effects on both bacteria colonization and translocation. Therefore,clinicians should try to reserve normal intestinal flora.