抗生素对新生大鼠肠道免疫发育影响及双歧杆菌干预的研究

目的 研究新生大鼠口服抗生素对肠道免疫发育的影响及双歧杆菌干预的效果.方法 选用50只7日龄新生SD大鼠,每组10只,随机分为5组:对照组(A)、抗生素组(B)、益生菌组(C)、益生菌干预组(D)和生理盐水组(E).A组为空白对照,B组给予头孢克洛灌胃,C组给予双歧杆菌灌胃,D组先给头孢克洛灌胃,2h后再灌长双歧杆菌,E组每天灌以等量的生理盐水,持续2周后处死大鼠,取少许新鲜盲肠内容物粪便涂片,免疫组化方法检测末端回肠肠组织中CD4、CD8的表达和组织学观察.结果 粪便涂片结果显示:B组与其余四组相比G+b占肠道总细菌数比率明显下降,G-b及G+c占总细菌数比率明显升高(P＜0.01).组织形态学观察:C组与E组肠黏膜绒毛和腺体发育良好,上皮结构完整,排列整齐,而A组腺体发育少,绒毛高度小；B组肠黏膜绒毛和腺体萎缩,黏膜水肿,部分上皮细胞变性、坏死、脱落；D组肠黏膜绒毛和腺体排列整齐绒毛显示清楚,少部分黏膜上皮细胞脱落、坏死.组肠组织中CD4、CD8的表达:B组CD4、CD8表达程度受到抑制,灰度值增大(P＜0.05)；C组与E组相比CD4、CD8表达增加,灰度值比较差异有统计学意义(P＜0.05).结论 肠道菌群的正常定植,刺激肠道免疫系统的发育.新生大鼠口服抗生素后肠黏膜结构被破坏以及干扰肠道菌群的定植,影响肠道免疫系统的发育.长双歧杆菌的能预防抗生素引起的菌群紊乱,维持肠道黏膜的完整性,保护肠道免疫系统的正常发育.

Influences of antibiotics on the intestinal flora and immune system development of neonatal rats

Objective To investigate the influence of antibiotics on the intestinal flora and immunity system development of neonatal rats. Methods 50 neonatal Sprague-Dawley rats （7 days old, weighing 15 - 21 g, male and female） were randomly divided into Control group （A）, Antibiotics group （B）, Probiotics group （C）, Probiotics intervention group （D） and saline group （E） , 10 rats in each group. Group B received a daily dose of 100 mg/kg of Cefaclor intragastrically; Group C were given Bifidobacterium longum intragastrically; Group D were given Cefaclor at first and then Bifidobaeterium longum after 2 hours; Group E were given equivalent volume of Sodium Chloride solution. The model-groups were administered once per day for 2 weeks. Group A were sacrificed at the beginning of the experiment without treatment. Eight rats, selected from each group at random, were sacrificed at the end of the experiment. The intestinal flora in Caecum luminal contents of the rats were counted by Fecal smears assay ; The CD4 ^＋ and CD8 ^＋ T cells and histology of terminal ileum tissue were detected by immunohisto-chemistry assay. Results Compared with Group A, C, D or E, the proportion of G^＋bacilli in the intestinal flora in Group B decreased obviously, but the proportion of G^- bacilli and G ^＋ cocci in Group B increased obviously （ P 〈 0.0 1 ）. In Group C and E, the epithelial lining of mucosal structure was in order and the villi and glands of mucosa were well developed, while in Group A, the glands hardly developed and the villus height was short. In Group B, the mueosal membrane was swelling; part of the epithelial cells appeared degeneration, necrosis and exfoliation, and the villi and glands showed atrophy. In Group D, the villi and glands of mucosal structure was clear and in order, with only a few epithelium cells exfoliation and necrosis. Compared with Group C, D or E, the expression of CD4 ^＋ , CD8 ^＋ T cells in group B was suppressed by antibiotics （P 〈 0.05）. The expression of CD4^＋ and CD8 ^＋ T cells in Group C was increased compared to Group E, with significant difference between the gray values （ P 〈 0.05 ）. Conclusion The intestinal colonization with a balanced mieroflora can stimulate the development of the intestinal immune system. Antibiotics administered orally at neonate stage may destroy mueosal structures and impair the normal intestinal flora colonization, which cause flora disturbance and thereby suppress the development of intestinal immune system. Bifidobacterium longum adminstration can prevent antibiotic-associated flora disorders, maintain the dynamic balance of intestinal flora, and protect the normal development of intestinal immune system.