Bacterial translocation and immunohistochemical measurement of gut immune function

Gut Barrier Disruption Secondary to Radiofrequency-Assisted Liver Parenchyma Resection in a Porcine Model

BACKGROUND

Radiofrequency-assisted liver resection (RF-LR) techniques minimize intraoperative blood loss, while avoiding the Pringle maneuver. Both surgical excision and radiofrequency ablation of liver parenchyma compromise gut barrier function with subsequent bacterial translocation. The present study sought to investigate in a porcine model the impact of two RF-LR techniques on the integrity and inflammatory response of the gut barrier.

METHODS

Twenty-four pigs were subjected to either (a) partial hepatectomy (PH) employing the "sequential coagulate-cut" technique using a monopolar electrode (SCC group), the one using the bipolar Habib-4X device (group H), or the "crush-clamp" technique (group CC) or (b) sham operation (group Sham). At 48-h post-operation, ileal tissue was excised to be subjected to histopathologic examination, histomorphometric analysis, and immunohistochemical assessment of the mitotic and apoptotic activities and the expression of interleukin-6 (IL-6), tumor necrosis factor-α (TNFα), and nuclear factor-κB (NFκΒ).

RESULTS

Histopathologic score increased in all PH groups, being higher in group SCC, while lower in group H. Villous height decreased in group SCC only. Mitotic index decreased, while apoptotic index increased in all PH groups. An increase in tissue expression score was noted for IL-6 in group CC, for TNFα in all PH groups, being lower in group H compared to group CC, and for NFκB in all PH groups.

CONCLUSIONS

The Habib-4X technique for liver resection proved to preserve the integrity of gut barrier, being less injurious in the intestinal mucosa compared to the SCC and CC techniques.

Differential Effect of Light and Dark Period Sleep Fragmentation on Composition of Gut Microbiome and Inflammation in Mice

Bi-directional interactions amongst the gut microbiota, immune system, and brain function are thought to be critical mediators of health and disease. The role sleep plays in mediating these interactions is not known. We assessed the effects of sleep fragmentation (SF) on the microbiota–gut–brain axis. Male C57BL/6NCrl mice (4 to 5 per cage, fed standard lab chow) experienced SF via mechanical stimulation at 2 min intervals during the light (SF) and dark (DD, dark disturbances) periods. Home cage (HC) controls were undisturbed. After 10 days, fecal samples were collected at light onset, midday, light offset, and midnight. Samples were also collected after 10 days without SF. Subsequently, the mice were randomized across groups and allowed 20 additional days of recovery followed by 10 days of SF or DD. To assess effects on the microbiota, 16S rRNA sequencing was used, and mesenteric lymph nodes (MLNs) and cortex and medial prefrontal cortex were analyzed using cytokine arrays. SF and DD produced significant alterations in the microbiota compared to HC, and DD had greater impact than SF on some organisms. SF produced marked suppression in MLNs of chemokines that regulate inflammation (CCL3, CCL4 and their receptor CCR5) and maintain the immune mucosal barrier (Cxcl13) at the same time that cortical cytokines (IL-33) indicated neuroinflammation. DD effects on immune responses were similar to HC. These data suggest that SF alters the microbiome and suppresses mucosal immunity at the same time that mediators of brain inflammation are upregulated. The translational implications for potential application to clinical care are compelling.

Inflammation and Overlap of Irritable Bowel Syndrome and Functional Dyspepsia

Irritable bowel syndrome (IBS) and functional dyspepsia (FD) are common functional gastrointestinal disorders (FGIDs) and account for a large proportion of consulting patients. These 2 disorders overlap with each other frequently. The pathogenesis of IBS or FD is complicated and multi-factors related, in which infectious or non-infectious inflammation and local or systemic immune response play significant roles. There are few studies focusing on the mechanism of inflammation in patients with overlap syndrome of irritable bowel syndrome and functional dyspepsia (IBS-FD). This review focuses on current advances about the role of inflammation in the pathogenesis of IBS and FD and the possible mechanism of inflammation in IBS-FD.

Alterations in intestinal microbiota relate to intestinal failure-associated liver disease and central line infections

BACKGROUND

The gut microbiota plays a vital role in modulating the metabolic and immune functions of the intestines. We aimed to analyze the dysbiosis of microbiota in infants with short bowel syndrome (SBS) with different complications.

PROCEDURE

We included 26 fecal samples from 18 infants with SBS during parenteral nutrition. The samples were categorized into three groups: asymptomatic, parenteral nutrition-associated liver disease (PNALD), and central line-associated bloodstream infection (CLABSI). Seven healthy infants were enrolled as controls. Fecal microbiota, secretory IgA, calprotectin, bile acids, and short chain fatty acids were detected.

RESULTS

The bacterial diversity of the Asymptomatic and Control Groups was significantly higher than that in the PNALD and CLABSI Groups. Proteobacteria was the most pronounced phylum in the PNALD and CLABSI Groups. Decreased acetate was observed in all SBS samples; however, fecal secretory IgA and calprotectin and the proportion of primary and secondary bile acids did not differ from those in healthy controls.

CONCLUSIONS

Marked alterations of the intestinal microbiota with decreased level of acetate were shown in SBS patients compared with healthy controls. Over-abundance of Proteobacteria (especially Enterobacteriaceae) was found in the samples from the PNALD and CLABSI Groups.

LEVEL OF EVIDENCE

Prognosis Study, Level I.

Disease dependent qualitative and quantitative differences in the inflammatory response to ascites occurring in cirrhotics

AIM: To assess differing patterns and levels of ascitic fluid cyctokine and growth factors exist between those with a high risk and low risk of spontaneous bacterial peritonitis (SBP).

METHODS: A total of 57 consecutive patients with ascites requiring a large volume paracentesis were studied. Their age, gender, specific underlying disease conditions were recorded after a review of their clinical records. Each underwent a routine assessment prior to their paracentesis consisting of a complete blood count, complete metabolic profile and prothrombin time/international normalized ratio (INR) determination. The ascitic fluid was cultured and a complete cell count and albumin determination was obtained on the fluid. In addition, blood and ascitic fluid was assessed for the levels of interleukin interleukin (IL)-1A, IL-1B, IL-2, IL-4, IL-8, IL-10, monocyte chemotactic protein (MCP)-1, tumor necrosis factor (TNF)-α, interferon (IFN)-γ, vascular endothelial growth factor (VEGF) and epidermal growth factor (EGF) utilizing the Randox Biochip platforms (Boston, MA). A serum-ascites gradient, for each cytokine and growth factor was calculated. The results are reported as mean ± SEM between disease groups with statistical analysis consisting of the student t-test (two tailed) with a P value of 0.05 defining significance.

RESULTS: No clinically important demographic or biochemical differences between the 4 groups studied were evident. In contrast, marked difference in the cytokine and growth factors levels and pattern were evident between the 4 disease groups. Individuals with alcoholic cirrhosis had the highest levels of IL-1A, IL-1B, IL-4, IFNγ. Those with malignant disease had the highest levels of IL-2. Those with hepatitis C virus (HCV) associated cirrhosis had the highest value for IL-6, IL-8, IL-10, MCP-1 and VEGF. Those with cardiac disease had the highest level of TNF-α and EGF. The calculated serum- ascites gradients for the cardiac and malignant disease groups had a greater frequency of negative values signifying greater levels of IL-8, IL-10 and MCP-1 in ascites than did those with alcohol or HCV disease.

CONCLUSION: These data document important differences in the cytokine and growth factor levels in plasma, ascitic fluid and the calculated plasma - ascites fluid gradients in cirrhotics requiring a large volume paracentesis. These differences may be important in determining the risk for bacterial peritonitis.

Probiotics can alleviate cardiopulmonary bypass-induced intestinal mucosa damage in rats

BACKGROUND

Cardiopulmonary bypass (CPB) is commonly applied to support circulation during heart surgery but frequently causes adverse effects.

AIMS

The purpose of this study was to examine the potential of probiotics to improve small intestinal mucosa barrier function after CPB.

METHODS

Twenty-four adult male SD rats were randomly divided into sham-operated (S), CPB-operated (CPB), and probiotic-fed (Y) groups. Diamine oxidase (DAO) activity and concentrations of D-lactic acid, endotoxin, TNFα, and IL-6 were measured in portal vein blood. IgA concentrations were determined in plasma and the small intestine. Vena cava blood and tissue samples were used to monitor bacterial growth. Intestinal epithelial ultrastructure was analyzed by transmission electron microscopy (TEM). Occludin and ZO-1 expression levels in the intestinal epithelium were detected by western blotting and immunohistochemistry, respectively.

RESULTS

D-lactic acid, endotoxin, TNFα and IL-6 levels, DAO activity, and bacterial translocation rate were increased (P < 0.05) in CPB and Y compared to the S group. The above indices were relatively lower (P < 0.05) in Y than in CPB. Plasma and small intestinal IgA levels were significantly lower (P < 0.05) in CPB, while in Y they were significantly increased (P < 0.05) but lower than in S (P < 0.05). These results were confirmed by TEM. Consistently, occludin and ZO-1 expression levels were significantly higher in Y than in CPB (P < 0.05) but still lower compared to S (P < 0.05).

CONCLUSION

Pre-administration of probiotics can improve, to some extent, intestinal barrier function after CPB in rats, and this effect is likely related to inhibition of the CPB-induced inflammatory response, improvement in local intestinal immune function, and increased expression of intestinal epithelial tight junction proteins.

Cirrhotic ascites review: Pathophysiology, diagnosis and management

Ascites is a pathologic accumulation of peritoneal fluidcommonly observed in decompensated cirrhotic states.Its causes are multi-factorial, but principally involve significant volume and hormonal dysregulation in the setting of portal hypertension. The diagnosis of ascites is considered in cirrhotic patients given a constellation of clinical and laboratory findings, and ultimately confirmed, with insight into etiology, by imaging and paracentesis procedures. Treatment for ascites is multi-modal including dietary sodium restriction, pharmacologic therapies, diagnostic and therapeutic paracentesis, and in certain cases transjugular intra-hepatic portosystemic shunt. Ascites is associated with numerous complications including spontaneous bacterial peritonitis, hepato-hydrothorax and hepatorenal syndrome. Given the complex nature of ascites and associatedcomplications, it is not surprising that it heralds increased morbidity and mortality in cirrhotic patients and increased cost-utilization upon the health-care system. This review will detail the pathophysiology of cirrhotic ascites, common complications derived from it, and pertinent treatment modalities.

Association Between Appendectomy and Fibrosis Progression in Nonalcoholic Fatty Liver Disease

Background

A two-hit theory explaining the progression of nonalcoholic fatty liver disease (NAFLD) to nonalcoholic steatohepatitis (NASH) and fibrosis is widely accepted. Endotoxins entering the portal vein from the gut are thought to be one cause of this second hit, and the literature frequently mentions associations between gut-derived endotoxins and progression of fibrosis in NAFLD. The appendix regulates intestinal immunity to protect the gut from the invasion of bacteria and antigens. Appendectomy may thus contribute to progression of fibrosis in NAFLD, but this association has not yet been clarified. We therefore investigated the association between appendectomy and progression of fibrosis in NAFLD.

Methods

Fifty two patients with NAFLD who underwent liver biopsy in our department were included in this study. Based on Brunt’s scores, patients with NAFLD were classified into a mild fibrosis group and advanced fibrosis group.

Results

History of appendectomy was found to be significantly more frequent in patients with advanced fibrosis than in patients with mild fibrosis (P = 0.014). Multivariate logistic analysis was conducted with age, sex, albumin, platelet count, steatosis grade, and history of appendectomy as covariates and advanced fibrosis as the dependent variable. Significant differences were identified for platelet count and history of appendectomy, identifying these as independent risk factors for advanced fibrosis in NAFLD patients. The odds ratio for appendectomy history was 39.415 (P = 0.044).

Conclusions

History of appendectomy was significantly more frequent in NAFLD patients with advanced fibrosis, suggesting that appendectomy may represent a risk factor for advanced fibrosis in NAFLD.

NOD2 gene variants are a risk factor for culture-positive spontaneous bacterial peritonitis and monomicrobial bacterascites in cirrhosis

BACKGROUND

Spontaneous bacterial peritonitis (SBP) is considered as result of bacterial translocation from the gastrointestinal lumen to the mesenteric lymph nodes and subsequent circulation. Variants of the NOD2 gene contribute to bacterial translocation and were associated with SBP in a recent study.

METHODS

We determined common NOD2 variants by TaqMan polymerase chain reaction and analysed the ascitic fluid neutrophil count and bacterial culture results in 175 prospectively characterized hospitalized patients with decompensated cirrhosis who underwent diagnostic paracentesis in two German centres.

RESULTS

Ten patients presented with culture-positive SBP, 19 with culture-negative SBP and six had bacterascites. Minor allele frequencies for R702W, G908R and 1007fs in subjects with sterile non-neutrocytic ascites were 3.2, 2.5 and 2.5% respectively. Patients with SBP [odds ratio (OR) 2.7; P=0.036], culture-positive SBP (OR 6.0; P=0.012) and bacterascites (OR 6.0; P=0.050) were more often carriers of NOD2 variants than patients with sterile non-neutrocytic ascites. The mutations 1007fs and G908R were associated with culture-positive SBP (P ≤ 0.005) and R702W with bacterascites (P=0.014). There was no significant association of NOD2 variants with culture-negative SBP (OR 1.6; P=0.493). In logistic regression, previous SBP, a higher model for end-stage liver disease (MELD) score and the presence of a NOD2 variant were independent predictors of ascitic fluid infection. The median survival was insignificantly shorter in patients with NOD2 variants (268 vs. 339 days; P=0.386). In patients without hepatocellular carcinoma at study entry (N=148), NOD2 was a predictor of survival after adjustment for the MELD score and age (hazard ratio 1.89; P=0.045).

CONCLUSION

NOD2 variants increase the risk for culture-positive SBP and bacterascites in cirrhosis and may affect survival.

The Relationship between Small-Intestinal Bacterial Overgrowth and Intestinal Permeability in Patients with Irritable Bowel Syndrome

BACKGROUND/AIMS

Small-intestinal bacterial overgrowth (SIBO) is a frequent finding in patients with irritable bowel syndrome (IBS). Many patients with IBS also have abnormal intestinal permeability, which is probably due to low-grade inflammation in the intestinal mucosa. Our aim was to verify the relationship between SIBO and small-intestinal permeability in IBS patients.

METHODS

A cohort of 38 IBS patients (20 women and 18 men; age range 16-70 years; mean age 40.2 years) with symptoms that fulfilled Rome-II criteria, and 12 healthy controls (5 women and 7 men; age range 25-52 years; mean age: 37.8 years) were recruited. All subjects underwent lactulose breath tests (LBTs) and intestinal permeability tests using the polyethylene glycol (PEG) 3350/400 retrieval ratio.

RESULTS

A positive LBT was found in 18.4% (7/38) of patients with IBS and 8.3% (1/12) of control subjects. Intestinal permeability was significantly increased in patients with IBS compared with the normal controls (0.82+/-0.09 vs 0.41+/-0.05 [mean+/-SD], respectively; p<0.05). However, the intestinal permeability did not differ significantly between IBS patients with a positive LBT and those with a negative LBT (0.90+/-0.13 and 0.80+/-0.11, respectively; p>0.05).

CONCLUSIONS

Intestinal permeability was increased in patients with IBS, but this finding did not correlated with the occurrence of SIBO.

Pretreatment with arginine preserves intestinal barrier integrity and reduces bacterial translocation in mice

OBJECTIVE

To evaluate the effects of arginine on intestinal barrier integrity and bacterial translocation (BT) in mice undergoing intestinal obstruction.

METHODS

Mice were divided into 3 groups, treated for 7 d before surgical intervention with isocaloric and isoprotein diets. The ARG group received a diet containing 2% arginine, the IO (intestinal obstruction) and Sham groups, standard chow diet. On the eighth day of treatment, all animals received diethylenetriamine pentaacetic acid (DTPA) solution labeled with 99mTechnetium (99mTc-DTPA) by gavage for intestinal permeability analysis. After 90 min, the animals were anesthetized and the terminal ileum ligated. The Sham group only underwent laparotomy. After 4, 8, and 18 h, blood was collected for radioactivity determination. Samples of ileum were collected 18 h after surgery for histological analysis. In another set of animals, BT was evaluated. After 7 d of treatment, all animals received 10(8) CFU/mL of 99mTc-E.coli by gavage; 90 min later they were submitted to the surgical procedure described above. BT was determined by the uptake of 99mTc-E.coli in blood, mesenteric lymph nodes, liver, spleen, and lungs, assessed 18 h after the surgery.

RESULTS

The intestinal permeability and BT were higher in the IO group when compared with the Sham group (P < 0.05). Arginine supplementation reduced intestinal permeability and BT to physiologic levels. Histological analysis showed mucosal ileum preservation in animals treated with arginine.

CONCLUSION

Arginine was able to preserve barrier integrity, thus reducing BT.

Advancement of intestinal function disorders in severe acute pancreatitis

Recent studies indicate that increased intestinal permeability and changes of intestinal mucosal immune function are very common in patients with severe acute pancreatitis (SAP). And they may be the main reasons for bacterial and endotoxin translocation, which are associated with secondary infection and multiorgan dysfunction syndrome in SAP. However, the accurate mechanism underlying the abnormality of intestinal mucosal immune dysfunction is not clarified, which deserves further study.

Effect of fructo-oligosaccharides and different doses of Bifidobacterium animalis in a weaning diet on bacterial translocation and Toll-like receptor gene expression in pigs

OBJECTIVE

Our aim was to study the possible synergic action of one prebiotic with increasing dietary doses of a probiotic strain of Bifidobacterium animalis on the translocation of bifidobacteria and on Toll-like receptor (TLR) gene expression in different organs of weaned piglets.

METHODS

Sixty-four pigs, reared from 21 to 35 d of age, were fed eight different diets according to a 2 x 4 factorial design: a control diet or the control diet supplemented with three different levels of B. animalis (10(7), 10(9), 10(11) colony-forming units/d), crossed with 0% or 2% sugar beet fructo-oligosaccharides. Pigs were then sacrificed, and the jejunum mucosa, ileocecal lymph nodes, and liver were sampled to determine the presence of Bifidobacterium spp. DNA and to quantify the expression of TLR2-, TLR4-, and tumor necrosis factor-alpha-encoding genes.

RESULTS

We found Bifidobacterium spp. genus-specific DNA in lymph nodes of subjects from all dietary treatments, including the control diet, but it increased with the bifidobacteria oral dose (P = 0.065). The linear effect of the dose of B. animalis on the expression of the TLR2-encoding gene in the lymph nodes was observed when fructo-oligosaccharides were added to the diet (P < 0.05). Tumor necrosis factor-alpha-encoding gene expression was positively correlated with TLR4- and TLR2-encoding gene expressions (P < 0.001 and P < 0.01, respectively) and negatively correlated with bifidobacteria DNA (P < 0.05). Moreover, the expression of the TLR4-encoding gene showed a positive correlation with TLR2-encoding gene expression (P < 0.001). In contrast, there was no correlation between expressions of the TLR2- and TLR4-encoding genes with the bifidobacteria DNA.

CONCLUSION

Soon after weaning, the translocation of the commensal bacteria in the ileocecal lymph nodes is a physiologic process. Moreover, diet affects the expression of the TLR2-encoding gene.

Small intestinal bacterial overgrowth in patients with interstitial cystitis and gastrointestinal symptoms

PURPOSE

Interstitial cystitis (IC) often coexists with irritable bowel syndrome (IBS). IBS may be explained by small-intestinal bacterial overgrowth (SIBO), which increases immune activation and visceral hypersensitivity. This prospective pilot study tested hypotheses that IC patients with gastrointestinal (GI) symptoms have SIBO, that nonabsorbable antibiotic use improves symptoms, and that improvement is sustained by prokinetic therapy.

METHODS

Consecutive IC patients with GI symptoms had lactulose breath testing (LBT). Those with abnormal results received rifaximin 1,200-1,800 mg/day for 10 days then tegaserod 3 mg/nightly. Questionnaires addressed IC and GI global improvement.

RESULTS

Of 21 patients, 17 (81%) had abnormal LBTs. Of 15 patients treated, GI global improvement was moderate to great in 11 (73%) and sustained in ten (67%). IC global improvement was moderate to great in six (40%) and sustained in seven (47%).

CONCLUSIONS

A majority of IC patients and GI symptoms had an abnormal LBT suggesting SIBO. Rifaximin improved symptoms, which was sustained by tegaserod.

Bacterial translocation: overview of mechanisms and clinical impact

Bacterial translocation (BT) is a phenomenon in which live bacteria or its products cross the intestinal barrier. Gut translocation of bacteria has been shown in both animal and human studies. BT and its complications have been shown clearly to occur in animal models, but its existence and importance in humans has been difficult to ascertain. We review the mechanisms of BT and its clinical impact based on the current literature.

The effects of long-term total parenteral nutrition on gut mucosal immunity in children with short bowel syndrome: a systematic review

BACKGROUND: Short bowel syndrome (SBS) is defined as the malabsorptive state that often follows massive resection of the small intestine. Most cases originate in the newborn period and result from congenital anomalies. It is associated with a high morbidity, is potentially lethal and often requires months, sometimes years, in the hospital and home on total parenteral nutrition (TPN). Long-term survival without parenteral nutrition depends upon establishing enteral nutrition and the process of intestinal adaptation through which the remaining small bowel gradually increases its absorptive capacity. The purpose of this article is to perform a descriptive systematic review of the published articles on the effects of TPN on the intestinal immune system investigating whether long-term TPN induces bacterial translocation, decreases secretory immunoglobulin A (S-IgA), impairs intestinal immunity, and changes mucosal architecture in children with SBS. METHODS: The databases of OVID, such as MEDLINE and CINAHL, Cochran Library, and Evidence-Based Medicine were searched for articles published from 1990 to 2001. Search terms were total parenteral nutrition, children, bacterial translocation, small bowel syndrome, short gut syndrome, intestinal immunity, gut permeability, sepsis, hyperglycemia, immunonutrition, glutamine, enteral tube feeding, and systematic reviews. The goal was to include all clinical studies conducted in children directly addressing the effects of TPN on gut immunity. RESULTS: A total of 13 studies were identified. These 13 studies included a total of 414 infants and children between the ages approximately 4 months to 17 years old, and 16 healthy adults as controls; and they varied in design and were conducted in several disciplines. The results were integrated into common themes. Five themes were identified: 1) sepsis, 2) impaired immune functions: In vitro studies, 3) mortality, 4) villous atrophy, 5) duration of dependency on TPN after bowel resection. CONCLUSION: Based on this exhaustive literature review, there is no direct evidence suggesting that TPN promotes bacterial overgrowth, impairs neutrophil functions, inhibits blood's bactericidal effect, causes villous atrophy, or causes to death in human model.The hypothesis relating negative effects of TPN on gut immunity remains attractive, but unproven. Enteral nutrition is cheaper, but no safer than TPN. Based on the current evidence, TPN seems to be safe and a life saving solution.

Bacterial translocation, endotoxaemia and apoptosis following Pringle manoeuvre in rats

BACKGROUND

Intraoperative occlusion of the hepatoduodenal ligament (Pringle manoeuvre (Pm)) is often employed for the reduction of blood loss during liver surgery. No data exist to date on the effects of Pm on mucosal barrier dysfunction, systemic bacterial translocation (BT), endotoxaemia and apoptosis.

MATERIALS AND METHODS

Sixty-five male Wistar rats in three groups: I (n=25) controls, II (n=20) sham operation, III (n=20) occlusion of the hepatoduodenal ligament (Pm). Tissue samples from mesenteric lymph nodes (MLNs), liver, lungs and spleen were analysed after 30 min and at 24 h. Endotoxin was measured in portal and aortic blood and routine haematological and biochemical parameters were measured before and after Pm.

RESULTS

No differences were found in the blood parameters before and after Pm, but a significant increase in contaminated MLNs and liver was noted. All cultured bacteria were enteric in origin. Portal and aortic endotoxin were significantly increased. Overall the ileal architecture remained intact in all specimens studied and no significant pathology was observed. The ABC increased after Pm significantly (P<0.01).

CONCLUSION

Normothermic Pm of 30 min duration results in immediate and delayed gut barrier failure by significantly increasing BT and endotoxaemia which might be attributed to portal stasis leading to intestinal congestion as well as temporary liver ischaemia. Apoptosis increased significantly 30 min after performing the Pm.

Intestinal adherent bacteria and bacterial translocation in breast-fed and formula-fed rats in relation to susceptibility to infection

The barrier function of the intestinal mucosa is immature in the newborn mammal, and is strengthened by breast milk. We investigated this effect of breast milk by comparing the susceptibility to infection assessed in terms of adherent bacterial colonization of the intestinal tissue (AdC) and bacterial translocation (BT) between breast-fed and formula-fed newborn rats. Three-day-old rat pups were assigned to one of three groups: mother-reared (MR), pseudo-cannulated (sham), and artificially reared (AR). AR rats were infused with formula through an intragastric cannula, under the control of a computer-regulated pumping machine. MR and sham rat pups were reared with their respective dams and received breast milk until weaning in a specially designed cage. In 10-d-old rats, there was no significant difference in the fecal or cecal flora between the AR and MR groups, whereas the AdC and the BT to the liver were greater in the AR than MR group. Enterobacteriaceae, Streptococcus and/or Enterococcus, and Staphylococcus were dominantly detected as microorganisms in AdC flora and BT. The AdC flora did not directly reflect the bacterial colonization flora. These findings suggest that AR rat pups mature normally, although there is a greater colonization of Enterobacteriaceae and BT in AR than MR pups. Consequently, the intestinal barrier function of the pups reared by artificial feeding may become susceptible to BT, and AdC may be more indicative than bacterial colonization of the susceptibility to BT.