AIM: To investigate the influences of enteral, parenteral nutrition and probiotics delivered by gut on intestinal microecology, epithelial tight junctions, immune and barrier function of rats with abdominal infection.METHODS: Rat abdominal infection models established with cecal ligation and perforation method, were divided into three groups: parenteral nutrition (PN group, n = 7), PN+enteral nutrition (EN group, n = 7) and PN EN + probiotics (probiotics group, n = 7) via the needle jejunostomy and neck vein for five days. The total nutritional supplement of the three groups was isonitrogenic and isocaloric. Probiotics was delivered by jejunostomy 10 mL/d (1 × 108 cfu/mL). The rats were killed on the sixth day. The feces in the cecum were cultured for anaerobic bacterial growth and analyzed with bacterial group DNA fingerprint profile with random amplified polymorphic DNA. The transmembrane binding proteins (occludin) and IgA level in plasma cells of intestine epithelium in colon and terminal ileum were measured by an immunohistochemistry method. The ultrastructure of intestinal epithelial tight junctions in colon and small intestine was observed by electronmicroscopy. Vena cava blood and the homogenated tissue of liver, lung and mesenteric lymph nodes were cultured to determine the bacterial translocations, and endotoxin in the blood from portal vein was detected.RESULTS: (1) The amount of bacteria of gut species in EN group and probiotic group was higher than that in PN group. The DNA-profiles in EN group and probiotic group were similar to that of normal rats. The number of DNAprofiles in probiotics group was much more than that in PN group and EN group. Moreover, there were strange stripes in PN group. (2) The expression of occludin and IgA in the small and large intestine in EN group (2.309± 0.336, 15.440 ± 2.383) and probiotic group (2.938 ±0.515, 16.230 ± 3.183) was improved as compared with PN group (1.207 ± 0.587, P ＜ 0.05, 11.189 ± 2.108, P ＜ 0.01). The expression of occludin in probiotic group (intestine: 2.93 ± 0.515; cecum: 3.40 ± 0.617) was higher than that in EN group (intestine: 2.309 ± 0.336;cecum: 2.076 ± 0.670; P ＜ 0.05). The expression of IgA, especially in EN group (intestine: 15.440 ± 2.383)and probiotic EN group (large intestine: 12.516± 1.542)significantly increased as compared with PN group (intestine: 11.189 ± 2.108; cecum: 10.160 ± 1.643;P ＜ 0.01). The intestinal epithelial tight junctions and microvilli of the probiotic group were more intact than those in the PN group. (3) The bacterial translocations in blood, liver, lung and mesenteric lymph nodes, and the levels of endotoxin were significantly reduced in probiotic (0.082 ± 0.029) and EN (0.125 ± 0.040) groups as compared with PN group (0.403 ± 0.181, P ＜ 0.05).CONCLUSION: Application of EN combined with probiotics could improve the expression of transmembrane binding proteins (occludin) and IgA,correct the intestinal flora disturbance, maintain gut barrier functions and tight junctions, and reduce the occurrence of gut bacterial translocation.