Bacterial Translocation In Mice Research Articles

A Dietary Nucleoside-Nucleotide Mixture Inhibits Endotoxin-Induced Bacterial Translocation in Mice Fed Protein-Free Diet

Nucleosides and nucleotides are important substrates utilized by the intestinal mucosa. To determine the relative effect of dietary nucleosides and nucleotides on the gut, we investigated the effects of these compounds on endotoxin-induced bacterial translocation, cecal bacterial populations and ileal histology in protein-malnourished mice. There was an inhibition of gram-negative enteric bacteria in the mesenteric lymph node and spleen of the surviving mice fed the protein-free diet supplemented with a nucleoside-nucleotide mixture compared with the nonsupplemented group. Histologically, the damage to the gut mucosal barrier was more pronounced in the nonsupplemented group than in the nucleoside-nucleotide supplemented group. However, the cecal bacterial populations in the groups were not different. The villous height, crypt depth and total wall thickness were more developed in the supplemented group compared with the nonsupplemented group, indicating that the nucleoside-nucleotide mixture blocked bacterial translocation by preventing endotoxin-induced mucosal or epithelial damage. These results suggest that the nucleoside-nucleotide mixture could be used to inhibit or reduce the incidence of bacterial translocation, decrease intestinal injury and improve survival in a lethal model of protein deficiency and endotoxemia.

Probiotics on Intestinal Flora Disturbance and Bacterial Translocation in Mice with Inflammatory Bowel Disease

Inflammatory bowel disease is becoming more and more common in western countries and less common in China. However, with the change of dietary structure, the incidence of inflammatory bowel disease is also increasing in China. It will cause abdominal pain, diarrhea and mucus, pus and blood, which are repeatedly delayed and difficult to alleviate. To explore the effectiveness of probiotics in the treatment of inflammatory bowel disease, Lactobacillus plantarum in probiotics and fifteen 8 w old female mice were selected for the experiment. We divided the mice into three groups: blank control group, interleukin-10 group and interleukin-10+Lactobacillus plantarum group. The interleukin-10+Lactobacillus plantarum group was gavaged with 0.5 ml of Lactobacillus plantarum bacterial solution (1.0×109 CFU/ml) every d. The blank control group and interleukin-10 group were gavaged with 0.5 ml of Ringer buffer for 4 consecutive w and compared the changes caused by Lactobacillus plantarum on Bifidobacterium, Lactobacillus, Clostridium perfringens and Enterobacter in the intestinal flora of mice and the changes caused by Lactobacillus plantarum on the intestinal flora effect of bacterial translocation in membranous lymph nodes and spleen. We found that the content of Enterobacter in the blank control group was the lowest at all three time points, with an average of 6. The content of Enterobacter in the interleukin-10+Lactobacillus plantarum group and the interleukin-10 group was 6.5 and 6.6 respectively, at the beginning of 0 w and 6.3 at the beginning of 2 w but after the 4 w, the content of Enterobacter in the two groups became 6.4 and 6.7, the difference increasedy.

Paneth Cell Dysfunction Mediates Alcohol-related Steatohepatitis Through Promoting Bacterial Translocation in Mice: Role of Zinc Deficiency.

Microbial dysbiosis is associated with alcohol-related hepatitis (AH), with the mechanisms yet to be elucidated. The present study aimed to determine the effects of alcohol and zinc deficiency on Paneth cell (PC) antimicrobial peptides, α-defensins, and to define the link between PC dysfunction and AH. Translocation of pathogen-associated molecular patterns (PAMPs) was determined in patients with severe AH and in a mouse model of alcoholic steatohepatitis. Microbial composition and PC function were examined in mice. The link between α-defensin dysfunction and AH was investigated in α-defensin-deficient mice. Synthetic human α-defensin 5 (HD5) was orally given to alcohol-fed mice to test the therapeutic potential. The role of zinc deficiency in α-defensin was evaluated in acute and chronic mouse models of zinc deprivation. Hepatic inflammation was associated with PAMP translocation and lipocalin-2 (LCN2) and chemokine (C-X-C motif) ligand 1 (CXCL1) elevation in patients with AH. Antibiotic treatment, lipopolysaccharide injection to mice, and in vitro experiments showed that PAMPs, but not alcohol, directly induced LCN2 and CXCL1. Chronic alcohol feeding caused systemic dysbiosis and PC α-defensin reduction in mice. Knockout of functional α-defensins synergistically affected alcohol-perturbed bacterial composition and the gut barrier and exaggerated PAMP translocation and liver damage. Administration of HD5 effectively altered cecal microbial composition, especially increased Akkermansia muciniphila, and reversed the alcohol-induced deleterious effects. Zinc-regulated PC homeostasis and α-defensins function at multiple levels, and dietary zinc deficiency exaggerated the deleterious effect of alcohol on PC bactericidal activity. Taken together, the study suggests that alcohol-induced PC α-defensin dysfunction is mediated by zinc deficiency and involved in the pathogenesis of AH. HD5 administration may represent a promising therapeutic approach for treating AH.

Effects of Short-Peptide-Based Enteral Nutrition on the Intestinal Microcirculation and Mucosal Barrier in Mice with Severe Acute Pancreatitis.

Short-peptide-based enteral nutrition (SPEN) is absorbed more efficiently in patients with severe acute pancreatitis (SAP). More importantly, SPEN decreases SAP-induced enterogenous infection risk. This study aims to investigate whether SPEN alleviates intestinal bacterial translocation in mice with SAP, and the underlying mechanisms. The SAP model is established after pre-treatment with SPEN or intact-protein-based enteral nutrition. Although there is no improvement in pancreas injury, as evaluated through Hematoxylin-Eosin staining or serum amylase, SPEN obviously attenuates intestinal bacterial translocation after SAP. To unveil the mechanisms, it is found that the intestinal mechanical barrier destroyed by SAP is significantly relieved by SPEN, which presents with recovered ZO-1 expression, mucus layer, and goblet cell function. Additionally, SPEN alleviates local CCR6/CCL20 induced CD11c+ dendritic cell infiltration, systemic immunosuppression, and inhibits the secretion of luminal secretory immunoglobulin A. Possibly responsible for SAP-induced mucosal dysfunctions, destroyed intestinal mucosal microcirculation and local hypoxia are largely improved in SAP+SPEN group. SPEN can improve downregulated intestinal mucosal microcirculation secondary to SAP, which may be responsible for mucosal inflammation relief, maintenance of the mechanical barrier and mucosal immunity, the correction of systemic immunosuppression, and play a protective role in defending commensal bacterial translocation after SAP.

Salmonella Outer Protein B Suppresses Colitis Development via Protecting Cell From Necroptosis.

Salmonella effectors translocated into epithelial cells contribute to the pathogenesis of infection. They mediate epithelial cell invasion and subsequent intracellular replication. However, their functions in vivo have not been well-identified. In this study, we uncovered a role for Salmonella outer protein B (SopB) in modulating necroptosis to facilitate bacteria escape epithelial cell and spread to systemic sites through a Salmonella-induced colitis model. Mice infected with SopB deleted strain ΔsopB displayed increased severity to colitis, reduced mucin expression and increased bacterial translocation. In vitro study, we found there was an increased goblet cell necroptosis following ΔsopB infection. Consistently, mice infected with ΔsopB had a strong upregulation of mixed lineage kinase domain-like (MLKL) phosphorylation. Deletion of MLKL rescued severity of tissue inflammatory, improved mucin2 expression and abolished the increased bacterial translocation in mice infected with ΔsopB. Intriguingly, the expression of sopB in LS174T cells was downregulated. The temporally regulated SopB expression potentially switched the role from epithelial cell invasion to bacterial transmission. Collectively, these results indicated a role for SopB in modulating the onset of necroptosis to increased bacteria pathogenesis and translocated to systemic sites.

Glucagon-like peptide-2 improves intestinal immune function and diminishes bacterial translocation in a mouse model of parenteral nutrition

Parenteral nutrition (PN) is associated with increased infectious risks due to impaired intestinal immunity. Although glucagon-like peptide-2 (GLP-2) enhances the gut barrier function, it is uncertain whether it improves mucosal immunologic barrier function. We hypothesized that injecting the PN mouse model with GLP-2 improved innate and acquired immunity, and prevented bacterial translocation. Forty-eight hours after venous cannulation, male Institute of Cancer Research mice were randomly divided into 3 groups based on their diet: chow with saline (n = 10), PN (n = 9), or PN + GLP-2 (30 μg bid per mouse, n = 10) provided for 5 days. Compared with chow, PN reduced interleukin (IL)-4 and IL-13 levels (P < .05, respectively), whereas, compared with PN alone, GLP-2 injection increased IL-4 and IL-13 levels (P < .05, respectively). Compared with chow, PN considerably suppressed, whereas GLP-2 improved, secretory phospholipase A2 and cryptdin-4 expression. PN, compared with chow, considerably decreased lysozyme and polymeric immunoglobulin receptor levels, whereas, compared with PN, GLP-2 significantly increased these protein levels (P < .01, respectively). In tissue and luminal samples, compared with chow, PN reduced secretory immunoglobulin A levels (P < .05), whereas, compared with PN alone, GLP-2 increased secretory immunoglobulin A levels (P < .05). Functionally, more bacterial translocation was observed in the PN group compared with the chow group (P < .001), and GLP-2 injection decreased bacterial translocation to chow levels (P < .05). In summary, GLP-2 treatment may improve intestinal innate and acquired immunity, and prevent bacterial translocation in mice on total parenteral nutrition.

Pretreatment and Treatment With L-Arginine Attenuate Weight Loss and Bacterial Translocation in Dextran Sulfate Sodium Colitis.

Imbalances in a variety of factors, including genetics, intestinal flora, and mucosal immunity, can contribute to the development of ulcerative colitis and its side effects. This study evaluated the effects of pretreatment or treatment with arginine by oral administration on intestinal permeability, bacterial translocation (BT), and mucosal intestinal damage due to colitis. C57BL/6 mice were distributed into 4 groups: standard diet and water (C: control group), standard diet and dextran sodium sulfate (DSS) solution (Col: colitis group), 2% L-arginine supplementation for 7 days prior to DSS administration and during disease induction (PT: pretreated group), and 2% L-arginine supplementation during disease induction (T: treated group). Colitis was induced by administration of 1.5% DSS for 7 days. After 14 days, intestinal permeability and BT were evaluated; colons were collected for histologic analysis and determination of cytokines; feces were collected for measurement of immunoglobulin A (IgA). The Col group showed increased intestinal permeability (C vs Col: P < .05) and BT (C vs Col: P < .05). In the arginine-supplemented groups (PT and T), this amino acid tended to decrease intestinal permeability. Arginine decreased BT to liver during PT (P < .05) and to blood, liver, spleen, and lung during T (P < .05). Histologic analysis showed that arginine preserved the intestinal mucosa and tended to decreased inflammation. Arginine attenuates weight loss and BT in mice with colitis.

Polymorphsims in the farnesoid X receptor modify the risk for spontaneous bacterial peritonitis in cirrhotic patients

The farnesoid X receptor (FXR) is involved in bacterial translocation in mice. In humans with liver cirrhosis, bacterial translocation can result in spontaneous bacterial peritonitis (SBP). We hypothesized that polymorphisms in the FXR gene (NR1H4) might influence the risk for SBP.

Morphine Induces Bacterial Translocation in Mice by Compromising Intestinal Barrier Function in a TLR-Dependent Manner

Opiates are among the most prescribed drugs for pain management. However, morphine use or abuse results in significant gut bacterial translocation and predisposes patients to serious infections with gut origin. The mechanism underlying this defect is still unknown. In this report, we investigated the mechanisms underlying compromised gut immune function and bacterial translocation following morphine treatment. We demonstrate significant bacterial translocation to mesenteric lymph node (MLN) and liver following morphine treatment in wild-type (WT) animals that was dramatically and significantly attenuated in Toll-like receptor (TLR2 and 4) knockout mice. We further observed significant disruption of tight junction protein organization only in the ileum but not in the colon of morphine treated WT animals. Inhibition of myosin light chain kinase (MLCK) blocked the effects of both morphine and TLR ligands, suggesting the role of MLCK in tight junction modulation by TLR. This study conclusively demonstrates that morphine induced gut epithelial barrier dysfunction and subsequent bacteria translocation are mediated by TLR signaling and thus TLRs can be exploited as potential therapeutic targets for alleviating infections and even sepsis in morphine-using or abusing populations.

Bifidobacteria may be beneficial to intestinal microbiota and reduction of bacterial translocation in mice following ischaemia and reperfusion injury

The aim of the present study was to determine the effect of peroral bifidobacteria on the intestinal microbiota, barrier function and bacterial translocation (BT) in a mouse model of ischaemia and reperfusion (I/R) injury. A total of twenty-four male BALB/c mice were randomly allocated into three groups: (1) sham-operated, (2) I/R and (3) I/R injury and bifidobacteria pretreatment (109 colony-forming units/d). Bifidobacteria were administered daily intragastrically for 2 weeks before induction of I/R. Subsequently, samples of caecal content, intestinal mucosa, ileal segments, blood, mesenteric lymph nodes (MLN) and distant organs (liver, spleen and kidney) were prepared for examination. In the I/R model, barrier dysfunction (caecal microbiota dysbiosis, disruption of tight junction (TJ), increased epithelial cell apoptosis, disruption of mucosa and multiple erosions) in the intestine was observed, associated with increased BT to extraintestinal sites. The ratio of BT to MLN and distant organs in mice exposed to I/R injury was 62·5 %, which was significantly higher than the sham-operated group. However, pretreatment of animals with bifidobacteria prevented I/R-induced BT, reduced pro-inflammatory cytokine release, the levels of endotoxin, intestinal epithelial cell apoptosis, disruption of TJ and increased the concentration of SCFA, resulting in recovered microbiota and mucosal integrity. Bifidobacteria may be beneficial in reducing BT in I/R injury of mice. Therefore, peroral administration of bifidobacteria is a potential strategy to prevent I/R-induced BT and intestinal barrier dysfunction.

Modulation of bacterial translocation in mice mediated through lactose and human milk oligosaccharides

Massive resection of the small intestine in infants is imposed to the regulation of several intestinal pathological situations, as intestinal adaptation cannot be relied upon. Many nutritional disturbances are occurring following surgery procedure. In this vein, long-term parenteral feeding is adopt to improve prognosis not always successfully. Clostridia and more specifically Clostridium perfringens, are suspected to participate in the physiopathology of the rising situation. In order to investigate the effect of lactose and human milk neutral oligosaccharides (HMNOs) on Clostridia, germfree mice were inoculated either with enterotoxigenic C.perfringens strain isolated from a patient with NEC, or with a human microbiota harboring C.clostridioforme group(HF). In this vein, different doses of lactose were administrated during 2 weeks in adult mice on an attempt to evaluate the lactase activity. Intake of lactose (70 g/L) and HMNOs (7 g/L) in C.perfringens monoassociated mice induced mortality within a week. In HF mice, no mortality was observed. An increase in Clostridia occurrence was observed in the median ileum after intake of 7 g lactose ( p = 0.017). Higher clostridial numbers occurred in caecum following intake of 70 g lactose ( p < 0.05) and HMNOs ( p < 0.025). Bifidobacteria were found increased from distal ileum to colon following 70 g of lactose intake, whereas they decreased in the caecum of mice drinking lower lactose concentrations. Finally, bacteremia was more frequent in 70 g lactose/L mice ( p < 0.02), whereas at lower doses of lactose bifidobacterial translocation was observed. As a result, human milk oligosaccharides could favor clostridial population when reaching the lower intestine. The shortness of the small intestine in infants underwent massive intestinal resection seems to be associated to an incomplete breakdown of lactose. Enteral feeds formulas deprived in lactose would be more suitable in enteral feeding of infants.

Gut Microbiota Dysbiosis Is Associated with Inflammation and Bacterial Translocation in Mice with CCl4-Induced Fibrosis

BackgroundGut is the major source of endogenous bacteria causing infections in advanced cirrhosis. Intestinal barrier dysfunction has been described in cirrhosis and account for an increased bacterial translocation rate.Hypothesis and AimsWe hypothesize that microbiota composition may be affected and change along with the induction of experimental cirrhosis, affecting the inflammatory response.Animals and MethodsProgressive liver damage was induced in Balb/c mice by weight-controlled oral administration of carbon tetrachloride. Laparotomies were performed at weeks 6, 10, 13 and 16 in a subgroup of treated mice (n = 6/week) and control animals (n = 4/week). Liver tissue specimens, mesenteric lymph nodes, intestinal content and blood were collected at laparotomies. Fibrosis grade, pro-fibrogenic genes expression, gut bacterial composition, bacterial translocation, host's specific butyrate-receptor GPR-43 and serum cytokine levels were measured.ResultsExpression of pro-fibrogenic markers was significantly increased compared with control animals and correlated with the accumulated dose of carbon tetrachloride. Bacterial translocation episodes were less frequent in control mice than in treated animals. Gram-positive anaerobic Clostridia spp count was decreased in treated mice compared with control animals and with other gut common bacterial species, altering the aerobic/anaerobic ratio. This fact was associated with a decreased gene expression of GPR43 in neutrophils of treated mice and inversely correlated with TNF-alpha and IL-6 up-regulation in serum of treated mice along the study protocol. This pro-inflammatory scenario favoured blood bacterial translocation in treated animals, showing the highest bacterial translocation rate and aerobic/anaerobic ratio at the same weeks.ConclusionsGut microbiota alterations are associated with the development of an inflammatory environment, fibrosis progression and bacterial translocation in carbon tetrachloride-treated mice.

Effect of CCL1 antisense ODN on bacterial translocation in mice irradiated with whole body 137Cs γ-rays: elimination of M2b macrophages in translocation sites (111.19)

Abstract Mice irradiated with 5 Gy whole body 137Cs γ-rays (WBI-mice) are shown to be carriers of M2bMϕ (IL-10+CCL1+LIGHT+IL-12- Mϕ), which are inhibitory on the host antibacterial innate immunities in bacterial translocation. M2bMϕ maintain their suppressor cell properties through the production of CCL1. In this study, therefore, we tried to eliminate M2bMϕ from mesenteric lymph nodes (MLN) of WBI-mice by CCL1 antisense ODN gene therapy. WBI-mice were treated with CCL1 antisense ODN with various doses (2, 10, 50, or 250 μg/mouse), routes (i.p., i.m. or s.c.) and schedules (twice a day for 2 to 7 days, starting 1 to 4 weeks after γ-irradiation). F4/80+ MLN-Mϕ isolated from these mice were identified as M2bMϕ by their abilities to express intracellular IL-10 and LIGHT mRNA. As a control, MLN-Mϕ were isolated from WBI-mice treated with scrambled ODN and subjected to the same test. In the results, the numbers of MLN-M2bMϕ were greatly reduced in WBI-mice treated s.c. with 10 to 50 μg/mouse of CCL1 antisense ODN twice a day for 2 days, 5 days or 7 days, started 1 to 3 weeks after γ-irradiation. However, MLN-M2bMϕ were detected in WBI-mice treated with CCL1 antisense ODN twice a day for 2 days started 4 weeks after the irradiation. These results indicate that M2bMϕ are eliminated from MLN of WBI-mice s.c. treated with CCL1 antisense ODN twice a day for 2 days starting 1 to 3 weeks after γ-irradiation.

Effect of CCL1 antisense ODN on bacterial translocation in mice irradiated with whole body 137Cs γ-rays: induction of M1 macrophages in translocation sites (111.21)

Abstract M1Mϕ (IL-10-IL-12+ Mϕ) in mesenteric lymph nodes (MLN) of mice have been identified as major effector cells in the host defense against enterococcal translocation and subsequent sepsis. However, M1Mϕ are not easily generated in 5 Gy whole body γ-irradiated mice (WBI-mice) whose M2bMϕ (IL-10+CCL1+LIGHT+IL-12- Mϕ) predominate. M2bMϕ are inhibitory on resident Mϕ conversion to M1Mϕ. In our previous studies, M2bMϕ were not demonstrated in MLN of WBI-mice treated with CCL1 antisense ODN. In this study, therefore, we tried to induce M1Mϕ by enterococcal antigen in MLN of WBI-mice treated with CCL1 antisense ODN. WBI-mice were treated s.c. with CCL1 antisense ODN (10 μg/mouse) twice a day for 2 days starting 2 weeks after γ-irradiation. One day after the final treatment, these mice were stimulated orally with 107 heat-killed E. faecalis. Two days after stimulation, F4/80+ MLN-Mϕ were isolated from these mice and tested for their M1Mϕ properties based on their abilities to express intracellular IL-12, CXCL9 and iNOS mRNA. In the results, Mϕ from WBI-mice treated with scrambled ODN did not express iNOS mRNA, intracellular IL-12 and CXCL9, even when these mice were stimulated with enterococcal antigen. However, iNOS+IL-12+CXCL9+ Mϕ were isolated from the same antigen-stimulated WBI-mice treated with CCL1 antisense ODN. These results indicate that M1Mϕ are inducible by the enterococcal antigen in WBI-mice treated with CCL1 antisense ODN.

Preventive effects of Schistosoma japonicum ova on trinitrobenzenesulfonic acid‐induced colitis and bacterial translocation in mice

To evaluate the preventive effects of Schistosoma japonicum ova on trinitrobenzenesulfonic acid (TNBS)-induced colitis and bacterial translocation in mice. BALB/c mice were randomly divided into three groups: control group; TNBS(+)Ova(-) group; and TNBS(+)Ova(+) group. Mice of the TNBS(+)Ova(+) group were exposed to 10 000 freeze-killed S. japonicum ova by i.p. injection on day 1 and day 11. On day 15, mice were challenged with TNBS to induce colitis. The following variables were assessed: colon pathological changes; serum expression of tumor necrosis factor-alpha (TNF-alpha), gamma-interferon (IFN-gamma) and interleukin-10 (IL-10); expression of Toll-like receptor 4 (TLR4) in colon; IFN-gamma, IL-10 and TLR4 mRNA expression in colon; and the bacterial translocation rate. Compared to TNBS(+)Ova(-) group, the colonic inflammation in the TNBS(+)Ova(+) group were relieved. A highly significant elevation of IFN-gamma and TNF-alpha were observed in the TNBS-induced colitis group. After exposure to the eggs, IFN-gamma was significantly decreased, while TNF-alpha was similar to that of the TNBS(+)ova(-) group. No obvious variation was seen in IL-10 expression in TNBS-induced colitis, compared to the controls. Exposure to the eggs led to a significant upregulation of IL-10 expression. TLR4 expression was elevated after injected with TNBS and was downregulated in the eggs group. Less intestinal bacterial translocation frequency was observed when exposed to eggs. S. japonicum ova can prevent the TNBS-induced colitis and reduce the bacterial translocation frequency in mice. The mechanisms were supposed to be due to the regulation of T-helper cell 1/2 balance and TLR4 expression.

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.

Cd1d-dependent regulation of bacterial colonization in the intestine of mice.

The accumulation of certain species of bacteria in the intestine is involved in both tissue homeostasis and immune-mediated pathologies. The host mechanisms involved in controlling intestinal colonization with commensal bacteria are poorly understood. We observed that under specific pathogen-free or germ-free conditions, intragastric administration of Pseudomonas aeruginosa, E. coli, Staphylococcus aureus, or Lactobacillus gasseri resulted in increased colonization of the small intestine and bacterial translocation in mice lacking Cd1d, an MHC class I-like molecule, compared with WT mice. In contrast, activation of Cd1d-restricted T cells (NKT cells) with alpha-galactosylceramide caused diminished intestinal colonization with the same bacterial strains. We also found prominent differences in the composition of intestinal microbiota, including increased adherent bacteria, in Cd1d-/- mice in comparison to WT mice under specific pathogen-free conditions. Germ-free Cd1d-/- mice exhibited a defect in Paneth cell granule ultrastructure and ability to degranulate after bacterial colonization. In vitro, NKT cells were shown to induce the release of lysozyme from intestinal crypts. Together, these data support a role for Cd1d in regulating intestinal colonization through mechanisms that include the control of Paneth cell function.

Effect of Probiotic Strains Lactobacillus acidophilus LAFTI L10 and Lactobacillus paracasei LAFTI L26 on Systemic Immune Functions and Bacterial Translocation in Mice

The immunostimulatory effects of Lactobacillus acidophilus LAFTI L10 and Lactobacillus paracasei LAFTI L26 were evaluated to determine their probiotic properties for functional food applications. Mice were given oral doses of either L. acidophilus L10 or L. paracasei L26 (108 CFU/50 μl/day), and the effects on immune responses and bacterial translocation were assessed after the 14-day feeding trial. The proliferative responses of splenocytes to concanavalin A and lipopolysaccharide were significantly higher in mice fed L. acidophilus. Concanavalin A–induced splenocyte proliferative responses increased significantly in mice fed L. paracasei. Interleukin 10 and interferon γ production from the splenocytes stimulated with concanavalin A were enhanced in mice fed L. acidophilus or L. paracasei. The phagocytic activity of the peritoneal macrophages was significantly higher in mice fed either L. acidophilus or L. paracasei compared with control mice. In mice fed L. acidophilus or L. paracasei, the bacterial translocation of Lactobacillus spp. and total anaerobes to Peyer's patches and mesenteric lymph nodes was modulated compared with that in the control mice. Furthermore, there was no indication of disruption of intestinal mucosal integrity and thus no bacterial translocation to spleen, liver, or blood in mice fed either L. acidophilus or L. paracasei. The results of this study indicate that L. acidophilus and L. paracasei are potential enhancers of systemic immunity and are nonpathogenic, as suggested by their bacterial translocation profiles in healthy mice.

Evidence that aminoguanidine inhibits endotoxin-induced bacterial translocation.

The role of inducible nitric oxide synthase (iNOS) in endotoxin-induced bacterial translocation was investigated by using its specific blocker aminoguanidine in 46 albino mice (25-35 g) allocated into four groups. The first group received intraperitoneal saline (control; 0.9 per cent w v(-1) sodium chloride 1 ml kg(-1); n=6), the second group intraperitoneal endotoxin (Escherichia coli lipopolysaccharide 055:B5 20 mg kg(-1); n=19), the third group intraperitoneal aminoguanidine (20 mg kg(-1), 20 min before and 12 h after saline; n=6) and the fourth group both endotoxin and aminoguanidine intraperitoneally (n=15). Some 24 h later, the animals were anaesthetized with ether and blood samples were collected by cardiac puncture together with mesenteric lymph node (MLN), spleen and liver specimens under aseptic conditions. Specimens were then cultured to determine the presence of colony-forming units as an index of bacterial translocation. No bacterial growth was detected in samples from the first and third groups. Colony-forming bacteria were found in ten of 14 MLN samples, eight of 14 spleens, four of 14 livers and three of 14 peripheral blood samples in the second group, with E. coli being the predominant pathogen. In contrast, in the fourth group, colony-forming bacteria were found in only three of 14 MLN samples (P=0.02 versus the second group), three of 14 spleens and one of 14 liver specimens. None of the values in the fourth group was significantly different from those in the saline control group. The inhibition of iNOS during endotoxaemia by its specific blocker aminoguanidine attenuates the incidence of bacterial translocation in mice. These results may be exploited clinically for the prophylaxis and treatment of septic states.

Modulation of Bacterial Translocation in Mice Mediated through ViableBifidobacterium breveor Cell-Free Whey Intake

The intake of high doses of viable bacteria called probiotics is a common alternative in the prevention or reduction of gastrointestinal disorders. However, the safety of probiotics has so far not been thoroughly ascertained. For this purpose, gut colonization, translocation and bacterial contamination of Peyer’s patches, heart blood, lungs, liver, kidneys and spleen were assessed in C3H conventional mice 2, 4 and 6 h post-intake of either water, Bifidobacterium breve C50 cells or cell-free whey. An analysis of variance (ANOVA) was performed by MANOVA and ANCOVA. Bifidobacterium breve C50 cells were never found in the intestine or in the internal organs. Lactobacilli numbers were increased in the caecum and colon, while Bacteroides fragilis group counts showed a decrease in the colon. A similar modification to caecal and colonic floras was demonstrated following cell-free whey intake, except in the case of the colonic Lactobacilli where no increase was observed. Translocation commonly occured in all mouse groups. The most common bacteria contaminating Peyer’s patches were lactobacilli. It is likely that they were of median and distal ileal origin (p=0.0001). ANOVA also suggested that lactobacilli from the distal ileum translocated to the liver (p=0.0001) and from the liver to the lungs (p=0.0027), according to the product the animals ingested. In conclusion, B. breve C50 cells that are unable to colonize the gut did not significantly increase the translocation of the indigenous ileal flora. However, their intake modified the flora in the lower part of the digestive tract to a greater extent than the cell-free whey.