| Objective:To investigate the influence of antibiotics administration on neonatal rat model of intestinal flora and immunity system development.Methods:50 neonate Sprague-Dawley rats(postnatal day 7,weighing 15～21g,male and female free) were divided into 5 groups that were 10 rats in each group at random in experiment:contract group(A),Antibiotic-treated group(B),Probiotics group(C), Probiotics intervention group(D),saline -treated group(E),and the latter four groups were model- groups.Rats in group B were received a daily dose of 100 mg/kg body weight of either a commercial form of Cefaclor(made by the PH 7.4 Sodium Chlorid,0.2ml per rat) by intragastric garage;group C were received Bifidobacterium longum(0.5 hundred million viable organism Per ml ) by intragastric gavage,0.2ml per rat;group D were received Cefaclor firstly(0.2ml),2 hours later received Bifidobacterium longum(0.2ml), total 0.4ml per rat;group E were received the equal Sodium Chloride solution(0.2ml per rat).The model-groups were administrated by above mentions 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 respectively at the end of the experiment.The intestinal flora in Caecum luminal contents of the rats were counted by Fecal smears assay;Relative content of four bacteria in stool in Caecum: bifidobacterium(BB),lactobacillus(LB),bacteroides fragilis(BF),clostridium(CL), were detected by the variation intestinal microflora by 16SrRNA fluorescent PCR;The CD4+,CD8+T cells of terminal ileum tissue were detected by immunohistochemistry assay.Results:1.Intestinal flora differential counting 1.1 The result display by Fecal smears assay:the amount of total intestinal bacterial in group A were less,but G+ bacillus took up absolutely dominant,G- bacillus relatively less, and slight G+ coccus and G- coccus could be found in group A,offering a typical bacteria distribution of Neonatal rat.Compared with group A,the amount of total intestinal bacteria in model-group were obviously increased,whereas among four groups,the proportion of G+ bacillus,G- bacillus,G+ coccus or G- coccus in the intestinal flora changed.The result showed:compared with group A,C,D or E,the proportion of G+ bacillus in the intestinal flora in group B decreased obviously,but the proportion of G- bacillus and G+ coccus in group B increased obviously,there were statistically significant difference among the groups(P＜0.01 );compared with group A or C,the proportion of G+ bacillus in group D or E decreased,the proportion of G- bacillus increased,there were statistically significant difference among these groups(P＜0.01);The proportion of G+ bacillus,G- bacillus,G+ coccus or G- coccus in the amount of total intestinal bacteria,there were no statistically significant difference between either group D and E,or group A and C;The proportion of G- coccus in the amount of total intestinal bacteria were no statistically significance difference among five groups.1.2 The change of relative content of four bacteria in stool in Caecum:compared with group C,D,the relative content of BB,LB lower,the relative content of CL higher in group B,there were statistically significant difference between the groups (P＜0.05);compared with group B,the relative content of BB higher,CL lower in group D,there were statistically significant difference between the groups(P＜0.05);the relative content of CL higher in group B than group D,there were statistically significant difference(P＜0.05);compared with group A,the relative content of BB higher,the relative of BF lower in group C,D or E,there were statistically significant difference(P＜0.05 );the relative content of BB higher in group C than group E or A,there were statistically significant difference(P＜0.05);the relative content of four bacteria were no statistically significant difference between D and E.2.The expression of CD4+,CD8+T cells of terminal ileum tissue Compared with group C,D or E,the expression of CD4+,CD8+T cells,which the gray values were increased,was suppressed in group B,There were statistically significant difference among the groups(P＜0.05);The expression of CD4+,CD8+T cells,which the gray values decreased comparison with group E,was increased in group C,There were statistically significant difference between the groups(P＜0.05);The expression of CD4+, CD8+T cells were no statistically significant difference between group D and E;except for group B,compared with the other three groups,the expression of CD4+,CD8+T cells decreased in group A,there were statistically significant difference among the groups (P＜0.05).Conclusions:1.The intestinal colonization with a balanced microflora can stimulate the normal development of the intestinal immune system.2.Antibiotics administration early in life may impair or influence the normal intestinal flora colonization,cause flora disturbance,thereby impair the development of intestinal immune system.3.The intervention of Probiotics(Bifidobacterium longum) can prevent the occurrence of antibiotic- associated bacteria disorders,maintain the dynamic balance of intestinal flora, and protect the normal development of intestinal immune system.4.Early supplementation of probiotics can increase the number of the dominant bacteria,thereby promote the intestinal immune system maturation process. |
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