烧伤后免疫抑制引起肠道细菌易位和脓毒症的病理学研究

近年来,创伤后体内细菌易位造成的内源性感染逐渐受到重视,为了探讨细菌易位的条件和途径等机理。本文利用烧伤后注射大剂量地塞米松的大鼠动物模型,模拟烧伤后应激状态下体内肾上腺皮质激素分泌增多,免疫机能下降的条件,观察肠道和其它脏器的病理改变。观察结果证实,烧伤与大剂量皮质激素确有引起肠道细菌易位和内源性感染,造成脓毒症的叠加作用。其基本条件包括肠道菌群微生态平衡的改变,宿主免疫机能下降和肠粘膜屏障的破坏。易位的肠道细菌主要是通过肠粘膜的坏死灶,上皮细胞坏变缺损处进入肠粘膜淋巴管和小静脉的。超微结构改变包括肠上皮细胞表面的微绒毛倒伏、变形、脱落、上皮细胞顶端崩解破坏,细胞间隙泡状增宽。脓肿中多数细菌微细结构完好,粒细胞和吞噬细胞胞浆中有多量糖元颗粒聚集,提示糖皮质激素可能影响吞噬细胞的糖代谢而降低其吞噬功能,使易位的细菌得以定植形成脓肿感染。

A Pathclogical Study of the Sepsis Caused by Experimental Drug Administration in White Rats Translocation of Intestinal Bacteria after Burn and Immunosuppressive

It has been noticed that endogenous infection and translocation of intestinal bacteria can be resulted from the suppression of host immune system induced by oversecretion of adrenocortical steroid hormone after burn stress. In order to study the path of translocation of intestinal bacteria and endogenous infections, an animal model of white rats was established by injecting large dose of Dexamethasone ( DXM ) after burn. It was found that the microorganisms penetrated across the mucosal barrier of the intestine caused 3. types of lesions: ( 1 ) focal necroses of intestinal mucosa; ( 2 ) defects of epithelia; and ( 3 ) gaps between epithelial cells.The bacteria entered the mucosa under the condition of rarefaction of the mucus secretion on the surface of the epithelia and a sparse population of lymphocytes, mononuclear phagocytes and neutrophilic granulocytes in lamina propria of the intestine. The translocating bacteria colonized in lymphatics or blood vessels in the intestinal wall, mesentery lymph nodes, liver, lungs and kidneys and form- ed abscesses in them. Under TEM, it was seen that the microbes which survived in the abscess: s had an intact appearance without obvious destruction and a lot of glycogen granules accumulated in the cytoplasm of granulocytes as well as mononuclear macrophages. It was suggested that there were some disturbances of glycogen motablism in the phagocytic system caused by DXM and stress by burn and a suppression of host immune reactions so that they were not able to eliminate the invading bacteria.