Time course of spontaneous bacterial translocation from gastrointestinal tract and its relationship to intestinal microflora in conventionally reared infant rats

Microbial Diversity and Community Variation in the Intestines of Layer Chickens

The intestinal microbiota is increasingly recognized as an important component of host health, metabolism and immunity. Early gut colonizers are pivotal in the establishment of microbial community structures affecting the health and growth performance of chickens. White Lohmann layer is a common commercial breed. Therefore, this breed was selected to study the pattern of changes of microbiota with age. In this study, the duodenum, caecum and colorectum contents of white Lohmann layer chickens from same environment control farm were collected and analyzed using 16S rRNA sequencing to explore the spatial and temporal variations in intestinal microbiota. The results showed that the diversity of the microbial community structure in the duodenum, caecum and colorectum increased with age and tended to be stable when the layer chickens reached 50 days of age and the distinct succession patterns of the intestinal microbiota between the duodenum and large intestine (caecum and colorectum). On day 0, the diversity of microbes in the duodenum was higher than that in the caecum and colorectum, but the compositions of intestinal microbes were relatively similar, with facultative anaerobic Proteobacteria as the main microbes. However, the relative abundance of facultative anaerobic bacteria (Escherichia) gradually decreased and was replaced by anaerobic bacteria (Bacteroides and Ruminococcaceae). By day 50, the structure of intestinal microbes had gradually become stable, and Lactobacillus was the dominant bacteria in the duodenum (41.1%). The compositions of dominant microbes in the caecum and colorectum were more complex, but there were certain similarities. Bacteroides, Odoribacter and Clostridiales vadin BB60 group were dominant. The results of this study provide evidence that time and spatial factors are important factors affecting the intestinal microbiota composition. This study provides new knowledge of the intestinal microbiota colonization pattern of layer chickens in early life to improve the intestinal health of layer chickens.

Effects of probiotics on ghrelin and lungs in children with acute lung injury: A double-blind randomized, controlled trial

AIM

To assess the effects of probiotics on serum ghrelin levels and protection for lungs in children with acute lung injury (ALI).

METHODS

This study was performed as a double-blind, randomized, and controlled trial in a pediatric intensive care unit (PICU). The eligible children with ALI were assigned to either probiotic treatment or an identical placebo for 10 days. Serum ghrelin, SP-A(surfactant protein-A), TNF-α, and IL-6 concentrations were assessed at baseline and at the end of trial. Meanwhile, pulmonary function test and echocardiography were examined, then VPEF (volume to peak tidal expiratory flow), TPEF/TE (the ratio of time taken to reach peak expiratory flow to total expiratory time), MAP (mean arterial pressure), and PAP (pulmonary artery pressure) were recorded.

RESULTS

Eighty participants fulfilled the study requirements with 40 children for each group. The groups were comparable in baseline characteristics. Serum SP-A, TNF-α, and IL-6 levels in the probiotic group were 212.6 ± 52.9 ng/mL, 401.9 ± 56.4 pg/mL, and 245.1 ± 55.1 pg/mL on day 10, respectively, significantly lower levels compared to the control group where the same parameters were 248.2 ± 57 ng/mL, 449.4 ± 60.1 pg/mL, and 308.3 ± 92.2 pg/mL (P < 0.01). However, ghrelin concentrations were elevated in the intervention group (P < 0.05). On measurement of pulmonary function, the probiotic group demonstrated a VPEF of 26.1 ± 4.2 mL and TPEF/TE of 29.1 ± 4.7%, which were higher than the control group (24.7 ± 4.3 mL and 26.9 ± 4.7%, respectively) (P < 0.05). MAP and PAP also improved in the probiotic group (P < 0.05). Furthermore, ghrelin, SP-A, TNF-α, IL-6, and PAP were negatively correlated. Positive correlations were found between ghrelin, TPEF/TE, and MAP. There were no probiotic-associated adverse events during the observation.

CONCLUSION

Probiotics administrated to children with ALI alleviates the inflammation of lungs, improves pulmonary function and circulation by ghrelin.

The Role of the Gut Microbiome on Chronic Kidney Disease

Chronic kidney disease (CKD) is estimated to affect nearly 500 million people worldwide and cardiovascular (CV) disease is a major cause of death in this population. However, therapeutic interventions targeting traditional CV risks are not effective at lowering the incidence of CV events or at delaying the progression of the disease in CKD patients. In recent years, disturbances of normal gut microbiome were recognized in the pathogenesis of diverse chronic diseases. Gut dysbiosis is being unraveled in CKD and pointed as a nontraditional risk factor for CV risk and CKD progression. The most often reported changes in gut microbiome in CKD are related to the lower levels of Bifidobacteriaceae and Lactobacillaceae and to higher levels of Enterobacteriaceae. Although metagenomics brought us an amplified vision on the microbial world that inhabits the human host, it still lacks the sensitivity to characterize the microbiome up to species level, not revealing alterations that occur within specific genus. Here, we review the current state-of-the-art concerning gut dysbiosis in CKD and its role in pathophysiological mechanisms in CKD, particularly in relation with CV risk. Also, the strategies towards prevention and treatment of gut dysbiosis in CKD progression will be discussed.

Oral tolerance failure upon neonatal gut colonization with Escherichia coli producing the genotoxin colibactin

The intestinal barrier controls the balance between tolerance and immunity to luminal antigens. When this finely tuned equilibrium is deregulated, inflammatory disorders can occur. There is a concomitant increase, in urban populations of developed countries, of immune-mediated diseases along with a shift in Escherichia coli population from the declining phylogenetic group A to the newly dominant group B2, including commensal strains producing a genotoxin called colibactin that massively colonized the gut of neonates. Here, we showed that mother-to-offspring early gut colonization by colibactin-producing E. coli impairs intestinal permeability and enhances the transepithelial passage of luminal antigen, leading to an increased immune activation. Functionally, this was accompanied by a dramatic increase in local and systemic immune responses against a fed antigen, decreased regulatory T cell population, tolerogenic dendritic cells, and enhanced mucosal delayed-type hypersensitivity response. Conversely, the abolition of colibactin expression by mutagenesis abrogates the alteration of oral tolerance induced by neonatal colonization by E. coli. In conclusion, the vertical colonization by E. coli producing the genotoxin colibactin enhances intestinal translocation and subsequently alters oral tolerance. Thus, early colonization by E. coli from the newly dominant phylogenetic group B2, which produces colibactin, may represent a risk factor for the development of immune-mediated diseases.

Oral antigen exposure in newborn piglets circumvents induction of oral tolerance in response to intraperitoneal vaccination in later life

Background

We previously determined that newborn piglets orally gavaged with Ovalbumin (OVA) responded to systemic OVA re-exposure with tolerance; if adjuvants were included in oral vaccine, piglets responded with antibody-mediated immunity (Vet Immunol Immunopathol 161(3–4):211–21, 2014). Here, we will investigate whether newborn piglets gavaged with a vaccine comprised of OVA plus unmethylated CpG oligodeoxynucleotides (CpG; soluble component; OVA/CpG) combined with OVA plus CpG encapsulated within polyphosphazene microparticles (MP; particulate component) responded with systemic and mucosal immunity. To monitor the response to systemic antigen re-exposure, piglets were i.p.-immunized with OVA plus Incomplete Freund’s Adjuvant (IFA) one month later.

Results

Newborn piglets (n = 5/group) were gavaged with a combined soluble and particulate vaccine consisting of OVA (0.5-0.05 mg) plus 50 μg CpG and 0.5 mg OVA plus 50 μg CpG encapsulated within a polyphosphazene MP (0.5 mg) referred to as OVA/CpG + MP. Control piglets were gavaged with saline alone. Piglets were i.p. immunized with 10 mg OVA (or saline) in IFA at four weeks of age and then euthanized at eight weeks of age. We observed significantly higher titres of serum anti-OVA immunoglobulin (Ig) IgM, IgA, IgG, IgG1, IgG2 and IgG in piglets immunized with 0.05 mg OVA/CpG + MP relative to saline control animals. Thus, a single oral exposure at birth to a combined soluble and particulate OVA vaccine including adjuvants can circumvent induction of oral tolerance which impacts response to i.p. vaccination in later life. Further, piglets gavaged with 0.05 mg OVA/CpG + MP generated significant anti-OVA IgG and IgG1 titres in lung compared to saline control piglets but results were comparable to titres measured in parenteral control piglets. Peripheral blood mononuclear cells (PBMCs) ex vivo-stimulated with OVA showed markedly decreased production of IL-10 cytokine after 72 hours relative to animal-matched cells incubated with media alone. No production of IFN-γ was observed from any groups.

Conclusion

Newborn piglets gavaged with low dose soluble and particulate OVA plus CpG ODN and polyphosphazene adjuvants produced antigen-specific antibodies in serum and lung after systemic re-exposure in later life. These data indicate circumvention of oral tolerance but not induction of oral immunity.

A single, low dose oral antigen exposure in newborn piglets primes mucosal immunity if administered with CpG oligodeoxynucleotides and polyphosphazene adjuvants

By definition, soluble antigens ingested orally trigger mucosal tolerance such that any subsequent re-exposure by a systemic route results in suppression of immunity. We propose that antigens introduced in extreme early life can readily traverse the gut wall and therefore circumvent induction of mucosal tolerance and instead induce immunity. Piglets were drenched with low-doses of ovalbumin (OVA; 5mg or 0.05 mg) alone, OVA plus adjuvants (CpG oligodeoxynucleotides and PCEP polyphosphazene) or saline within 6h of birth. At 28 days of age, they were administered 10mg OVA plus 1:1 Montanide adjuvant (or saline) via the intraperitoneal (i.p.) route or via the oral route. Serum was obtained on day 28 and day 49 to measure OVA-specific antibodies titres. All piglets boosted orally with OVA plus Montanide, regardless of prior OVA exposure, failed to induce immunity. As expected, piglets drenched with saline but boosted via the i.p. route with OVA plus Montanide showed significant induction of anti-OVA IgA, IgG, IgG1 and IgG2 relative to saline control piglets. Newborn animals drenched with 5mg or 0.05 mg OVA failed to induce oral immunity. A second intramuscular injection in adulthood triggered immunity in the piglets that were drenched with 0.05 mg OVA and boosted initially by the i.p. route suggesting that some systemic lymphocytes were primed despite initial lack of induction of humoral immunity. In contrast, piglets orally immunized with 5mg or 0.05 mg OVA plus adjuvants resulted in significant induction of anti-OVA IgA (5mg only), IgM, IgG, IgG1 and IgG2 in serum relative to saline control piglets as well as significant induction of anti-OVA IgA, IgM (5mg only) IgG, IgG1 (5mg only) or IgG2 relative to piglets drenched with OVA alone. These data clearly show that the response was sensitive to the oral vaccine components and was not simply a response to the i.p. immunization at day 28. This work demonstrates that newborn piglets respond to oral antigens with immunity if re-exposure to the antigen occurs via a systemic route and if adjuvants are included with the oral vaccine administered at birth. These results should be further explored to establish whether early life oral vaccination can be exploited to protect this susceptible population against infectious diseases.

Early methanogenic colonisation in the faeces of Meishan and Yorkshire piglets as determined by pyrosequencing analysis

Gut methanogenic archaea of monogastric animals are considered to be related to energy metabolism and adipose deposition of the host; however, information on their development in young piglets is limited. Thus, to investigate early methanogenic colonisation in the faeces of Meishan and Yorkshire piglets, faecal samples were collected from piglets at 1, 3, 7, and 14 days after birth and used to analyse the methanogenic community with 16S rRNA gene pyrosequencing. Results showed that the diversity of the methanogenic community in the faeces of neonatal piglets decreased from one to 14 days of age, as the total methanogen populations increased. The age of piglets, but not the breed, significantly affected the diversity of the methanogenic community which was dominated by the genus Methanobrevibacter. From the ages of one to 14 days, the abundance of M. smithii-related operational taxonomic units (OTUs) increased significantly, while the abundances of M. thaueri- and M. millerae-related OTUs decreased significantly. The substitution of M. smithii for M. thaueri/M. millerae was faster in Yorkshire piglets than in Meishan piglets. These results suggest that the early establishment of microbiota in neonatal piglets is accompanied by dramatic changes in the methanogenic community, and that the changes vary among pigs of different genotypes.

Low dose antigen exposure for a finite period in newborn rats prevents induction of mucosal tolerance

Background

In adult rats, initial exposure to antigens by a mucosal route triggers tolerance such that any subsequent re-exposure, even by a systemic route, results in suppression of immunity. The newborn’s gut is semi-permeable for a finite period to allow maternal antibodies to enter the newborn’s circulation. We propose that antigens introduced in extreme early life can readily traverse the gut wall and therefore circumvent induction of mucosal tolerance.

Methodology/Principle Findings

Rat pups were gavaged with low-doses of ovalbumin (OVA; oral exposure group) or saline (parenteral control group) every second day for several weeks followed by an intraperitoneal (i.p.) injection at 1 month of age. When gavage was initiated the day after birth, newborn oral exposure pups responded with significantly higher anti-OVA IgA, IgM, IgG2a, and IgG1 titres in their serum and anti-OVA IgA, IgG2a and IgG1 titres in their lungs compared to negative control pups. Oral exposure alone failed to induce immunity. Pups exposed to the same treatment regimen starting at 14 days of age showed induction of mucosal tolerance after i.p. immunization. Newborn oral exposure groups subjected to secondary i.p. immunization responded with significantly increased humoral immunity in lung and sera suggesting that once antigen-specific mucosal tolerance if circumvented, it persists. Lymphocytes derived from mesenteric lymph node cells re-simulated with OVA ex vivo, from newborn oral exposure pups exposed to secondary immunization produced significantly higher IFN-γ expression and lymphocyte proliferation relative to control pups indicating prevention of tolerance in the cell-mediated immune system.

Conclusions/Significance

This work demonstrates that newborns may be uniquely qualified to prevent induction of mucosal tolerance to oral antigens. These results should be further explored to establish whether prevention of tolerance by early life oral vaccination can be exploited to prime for mucosal as well as systemic immunity and thus protect this susceptible population against infectious diseases.

Modeling the interactions of bacteria and Toll-like receptor-mediated inflammation in necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is a severe disease of the gastrointestinal tract in premature infants, characterized by a disrupted intestinal epithelium and an exaggerated pro-inflammatory response. Since the activation of Toll-like receptor-4 (TLR4) blocks cell migration and proliferation and contributes to an uncontrolled inflammatory response within the intestine, this receptor has been identified as a key contributor to the development of NEC. Toll-like receptor-9 (TLR9) has been shown to sense bacterial genome components (CpG DNA) and to play an anti-inflammatory role in NEC. We present in vitro results demonstrating direct inhibition of TLR4 activation by CpG DNA, and we develop a mathematical model of bacteria-immune interactions within the intestine to investigate how such inhibition of TLR4 signaling might alter inflammation, associated bacterial invasion of tissue, and resulting outcomes. The model predicts that TLR9 can inhibit both the beneficial and detrimental effects of TLR4, and thus a proper balance of action by these two receptors is needed to promote intestinal health. The model results are also used to explore three interventions that could potentially prevent the development of NEC: reducing bacteria in the mucus layer, administering probiotic treatment, and blocking TLR4 activation. While the model shows that these interventions would be successful in most cases, the model is also used to identify situations in which the proposed treatments might be harmful.

Gut bacterial translocation contributes to microinflammation in experimental uremia

BACKGROUND

Microinflammation frequently develops in chronic uremia with pathological intestinal changes. However, the relationship between gut bacterial translocation and microinflammation in uremia has not been widely investigated.

AIM

This study aimed to investigate whether gut microbiome dysbiosis and translocation occurred in experimental uremia, and whether they consequently contributed to microinflammation.

METHODS

Forty rats underwent surgical renal mass 5/6 ablation. The surviving (uremic group, n = 21) and healthy (sham group, n = 20) rats were used in the experiment. Postoperative blood, livers, spleens, and mesenteric lymph nodes (MLNs) were subjected to bacterial 16S ribosomal DNA amplification to determine if bacteria were present. Bacterial genomic DNA samples from the MLNs and colon were amplified with specific primers designed by the 16S rRNA sequence of the species obtained from blood, livers, and spleens. Pyrosequencing was used to analyze the colonic microbiome of each subject. Intestinal permeability to (99m)Tc-DTPA, plasma hs-CRP, and IL-6 were measured.

RESULTS

Bacterial DNA in extraintestinal sites and altered colonic microbiomes were detected in some rats in the uremic group. Bacterial genomic DNA in MLNs and colon were obtained by primers specific for bacterial species observed from blood, livers, and spleens of identical individuals. Intestinal permeability, plasma hs-CRP, and IL-6 levels were statistically higher in the uremic group compared with the sham group. Plasma hs-CRP and IL-6 were significantly higher in uremic rats with bacterial DNA in their blood than in those without.

CONCLUSIONS

Gut microbiome dysbiosis occurs and bacteria translocate to the systemic and lymph circulation, thereby contributing to microinflammation in experimental uremia.

Gut microbial translocation in critically ill children and effects of supplementation with pre- and pro biotics

Bacterial translocation as a direct cause of sepsis is an attractive hypothesis that presupposes that in specific situations bacteria cross the intestinal barrier, enter the systemic circulation, and cause a systemic inflammatory response syndrome. Critically ill children are at increased risk for bacterial translocation, particularly in the early postnatal age. Predisposing factors include intestinal obstruction, obstructive jaundice, intra-abdominal hypertension, intestinal ischemia/reperfusion injury and secondary ileus, and immaturity of the intestinal barrier per se. Despite good evidence from experimental studies to support the theory of bacterial translocation as a cause of sepsis, there is little evidence in human studies to confirm that translocation is directly correlated to bloodstream infections in critically ill children. This paper provides an overview of the gut microflora and its significance, a focus on the mechanisms employed by bacteria to gain access to the systemic circulation, and how critical illness creates a hostile environment in the gut and alters the microflora favoring the growth of pathogens that promote bacterial translocation. It also covers treatment with pre- and pro biotics during critical illness to restore the balance of microbial communities in a beneficial way with positive effects on intestinal permeability and bacterial translocation.

Intrauterine growth restriction not only modifies the cecocolonic microbiota in neonatal rats but also affects its activity in young adult rats

OBJECTIVE

Elucidating why intrauterine growth restriction (IUGR) predisposes to some intestinal pathologies would help in their prevention. Intestinal microbiota could be involved in this predisposition; its initial setup is likely to be altered by IUGR because IUGR delays perinatal intestinal development and strongly interacts with intestinal physiology. Furthermore, because initial colonization determines adult intestinal microbiota, an IUGR-induced defect in initial microbiota would have long-term consequences. Thus, to characterize the effect of IUGR on intestinal microbiota, we compared the composition and activity of cecocolonic microbiota from birth to adulthood in rats with and without IUGR.

MATERIALS AND METHODS

IUGR was induced by gestational isocaloric protein restriction. Pups were fed by unrestricted lactating mothers. At different ages (days 5, 12, 16, 22, 40, and 100), cecocolonic contents from rats with IUGR and controls were analyzed for concentrations of bacterial end products and numbers of main bacterial groups, and submitted to in vitro fermentation tests.

RESULTS

IUGR affected gut colonization: bacterial density was increased at day 5 and decreased at day 12. In adulthood, rats with IUGR still differed from controls, harboring fewer Bifidobacterium sp at day 40 and more bacteria related to Roseburia intestinalis at day 100. In vivo, propionate concentration was decreased by IUGR before weaning, whereas the concentrations of other short-chain fatty acids were decreased at day 40, although the in vitro metabolic capability was unaffected overall.

CONCLUSIONS

We showed that IUGR induced, per se, some neonatal and long-lasting alterations of the intestinal microbiota. The physiological consequences of these changes and their relation to the predisposing effect of IUGR to gut pathologies must now be explored.

Impact of experimental colitis on hepatobiliary transporter expression and bile duct injury in mice

BACKGROUND AND AIMS

The pathogenetic link between ulcerative colitis and sclerosing cholangitis (SC) is unclear. We hypothesized that colitis induces changes in bile composition via inflammation-induced reduction of hepatobiliary transporter gene expression, ultimately resulting in cholestasis and bile duct injury.

METHODS

Alterations in transporter expression and bile secretion in acute dextran sulphate sodium (DSS)-induced colitis were compared with lipopolysaccharide (LPS)-treated mice serving as positive control. Whether chronic DSS-colitis elicits cholangitis in genetically predisposed animals was studied in heterozygous multidrug resistance gene 2 knockout mice (Mdr2(+/-)).

RESULTS

LPS but not DSS-colitis changed major hepatobiliary transporters (Ntcp, Bsep, Mrp2-4, Ostalpha/beta, Abcg5/8, Oatp1-4, Mdr1b and Mdr2), enzymes (Cyp3a11 and Cyp7a1), nuclear receptors (RXRalpha, FXR, CAR and PXR) and proinflammatory mediators (tumour necrosis factor alpha and inducible nitric oxide synthase). Formation of toxic bile reflected by an increased bile acid/phospholipid ratio was observed neither in acute nor in chronic colitis, although heterozygous Mdr2(+/-) mice developed mild portal inflammation after chronic colitis.

CONCLUSIONS

In contrast to LPS, DSS-colitis has a minor impact on hepatobiliary gene expression and bile secretion. Therefore, intestinal inflammation-associated changes of hepatobiliary transporter expression do not play a pathogenetic role in SC.

Age-related effects of the probiotic bacterium Lactobacillus plantarum 299v on gastrointestinal function in suckling rats

The effect of a probiotic bacterium on gut function was studied in neonatal animals by using a model with suckling rats. Lactobacillus plantarum 299v (Lp299v) or saline (controls) was fed (3.0 x 10(6) CFU/g b.wt per day) for one week to rats aged either 3, 7 or 14 days, after which bacterial colonization, gut growth, and functional parameters were analyzed. In rats fed with Lp299v from 3 to 10 days of age, an increase in ceacal lactobacilli was correlated with reduced intestinal macromolecular permeability and increased mucosal protein compared to age-matched controls. Pups treated from 7 to 14 days of age showed a decrease in pancreas weight and protein content, whereas pups treated from 14 to 21 days of age showed little effect of the Lp299v treatment. The results indicated that the bacterial exposure affected the gut function, where the effects were age-related and the youngest rats appeared most sensitive.

Maternal consumption of Lactobacillus plantarum 299v affects gastrointestinal growth and function in the suckling rat

After birth, the gastrointestinal (GI) tract undergoes vast structural and functional adaptations to be able to digest mother's milk and later, during the weaning period, solid food. Studies on germ-free animals have shown the role of the gut microbiota for stimulating GI maturation, but which groups are involved is unclear. In the present study, we administered the probiotic bacterium, Lactobacillus plantarum 299v (Lp299v), in the drinking water to pregnant and lactating rat dams until their pups had reached an age of 14 d. It was found that Lp299v colonizing the mothers were also able to colonize the pups, which had an impact on their gut growth and function. The small intestine, pancreas and liver weighed more in the 14 d-old pups born from dams exposed to Lp299v than in the control pups from dams given only water. Furthermore, the Lp299v pups showed decreased gut permeability. Despite a heavier spleen in the Lp299v pups, as compared to the control pups, no significant increase in the acute-phase protein, haptoglobin, was found. In conclusion, the results reported here clearly show that manipulating the maternal microflora by exposing expecting mothers to a Gram-positive, probiotic bacterium prior to parturition and during lactation impacts the gut growth and function in the offspring.

Microbial manipulation of the rat dam changes bacterial colonization and alters properties of the gut in her offspring

The impact of an altered bacterial colonization on gut development has not been thoroughly studied, despite the increased risk of certain diseases with a disturbed microbiota after birth. This study was conducted to determine the effect of microbial manipulation, i.e., antibiotic treatment or Escherichia coli exposure, of the dam on bacterial colonization and gut development in the offspring. Pregnant rats were administered either broad-spectrum antibiotics 3 days before parturition or live nonpathogenic E. coli Culture Collection of University of Göteborg, Sweden type strain (CCUG 29300(T)) 1 wk before parturition and up to 14 days of lactation in the drinking water. Cecal bacterial levels, gut growth, intestinal permeability, digestive enzyme levels, and intestinal inflammation were studied in 2-wk-old rats. Pups from dams that were antibiotic-treated had higher densities of Enterobacteriaceae, which correlated with a decreased stomach growth and function, lower pancreatic protein levels, higher intestinal permeability, and increased plasma levels of the acute phase protein, haptoglobin, compared with pups from untreated mothers. Exposure of pregnant/lactating mothers to E. coli CCUG 29300(T), also resulting in increased Enterobacteriaceae levels, gave in the offspring similar results on the stomach and an increased small intestinal growth compared with the control pups. Furthermore, E. coli pups showed increased mucosal disaccharidase activities, increased liver, spleen, and adrenal weights, as well as increased plasma concentrations of haptoglobin. These findings indicate that disturbing the normal bacterial colonization after birth, by increasing the densities of cecal Enterobacteriaceae, appears to have lasting effects on the postnatal microflora, which affects gut growth and function.

Increased bacterial permeation in long-lasting ileoanal pouches

BACKGROUND AND AIMS

Bacterial overgrowth appears to play an important role in the pathogenesis of ileoanal pouches. Therefore, the capability of bacterial permeation and its determinants is of great interest. The aim of this study was to examine bacterial permeation in the ileoanal pouch and to correlate the results with the degree of inflammation, the epithelial resistance, the mucosal transport function, and the age of the ileoanal pouches.

MATERIALS AND METHODS

Biopsies were taken from 54 patients before colectomy (n = 13; preileal pouch-anal anastomosis [IPAA]), and closure of ileostomy (n = 7; deviation), <1 year after closure of ileostomy (n = 8; intact pouch I), >1 year after closure of ileostomy (n = 16; intact pouch II), in the case of pouchitis (n = 11), and in 11 controls. Tissues were mounted in a miniaturized Ussing chamber. Escherichia coli was added to the mucosal side of the Ussing chamber, and the permeation was proven by serosal presence of E. coli. Epithelial and subepithelial resistance was determined by transmural impedance analysis. Active Na-glucose cotransport and active Cl secretion were measured. Specimens were analyzed by fluorescent in situ hybridization with oligonucleotide probes targeting the bacterial 16s ribosomal RNA. The bacteria in and on the tissue were enumerated.

RESULTS

Bacterial permeation occurred in 2 of 13 pre-IPAA, 2 of 7 deviations, 0 of 8 intact pouch I, 9 of 16 intact pouch II, 5 of 11 pouchitis specimens, and 0 of 11 ileum controls. The frequency of bacterial permeation in the intact pouch II group is higher than in the intact pouch I group (P < 0.001). Epithelial resistance, mannitol fluxes, electrogenic chloride secretion, sodium-glucose cotransport of the bacterially permeated specimens versus nonpermeated of the intact pouch II group, and the pouchitis group and subepithelial resistance remained unchanged. Intramural bacteria could be detected by fluorescence in situ hybridization mainly in long-lasting pouches, but there was no correlation with bacterial permeation.

CONCLUSIONS

The long-lasting ileoanal pouch is associated with increased bacterial permeability. This is not correlated with a disturbed function of the pouch mucosa but could be a precursor of pouchitis.

Neonatal maternal separation causes colonic dysfunction in rat pups including impaired host resistance

Previous studies have shown that early life stress in the form of intermittent maternal separation (MS) predisposes adult rats to develop stress-induced intestinal mucosal dysfunction and visceral hypersensitivity. However, the mechanism involved in the functional abnormalities is unclear. Our aim was to study immature animals during or shortly after exposure to MS to determine whether there are early pathophysiological changes in the gut. Sprague-Dawley rat pups were individually separated from the dam for 3 h/d from 4 to 21 d of age; nonseparated (NS) control pups remained in the home cage with the dam. On d 19-20, d 24-25, and d 29-30, blood was collected for corticosterone measurement, and colonic tissues were removed for functional and morphologic assessment. Corticosteroid levels were elevated in MS pups compared with NS, indicating that MS was indeed stressful. The distal colon demonstrated significantly enhanced ion secretion and macromolecular permeability at d 19-20 and d 24-25, returning to normal by d 29-30. Electron microscopy and bacterial culture studies indicated bacteria adhering to and penetrating into the colonic epithelium of the MS pups at all time points, while such events were rare in NS pups. The pathophysiological changes were inhibited by injecting pups sc with a corticotropin-releasing hormone (CRH) receptor antagonist daily during MS. Our studies indicate that early psychological trauma predisposes neonatal rats to develop persistent mucosal barrier dysfunction, including impaired host defense to luminal bacteria, by a mechanism involving peripheral CRH receptors.

Isomalto-oligosaccharides polarize Th1-like responses in intestinal and systemic immunity in mice

Isomalto-oligosaccharides (IMO) belong to a group of prebiotics that significantly increase the number of protective gut microflora. In the present study, we investigated the effects of IMO on intestinal and systemic immunity in mice. When mice were fed a diet supplemented with 20% IMO for 4 wk, the number of lactobacilli and the levels of IgA in feces were greater than those of mice fed the control diet (P < 0.05). Interferon-gamma (IFN-gamma) production by intestinal intraepithelial lymphocytes (i-IEL) in response to T-cell receptor (TCR) triggering was greater in mice fed IMO than in controls (P < 0.05), indicating T helper-1 (Th1) polarization of intestinal immunity by IMO. The proportion of natural killer (NK) T cells in the liver mononuclear cells (MNC), and the production of IFN-gamma by the liver MNC in response to TCR triggering were greater in mice fed IMO than in controls (P < 0.05), suggesting that the Th1/Th2 balance was shifted toward the Th1 lineage by IMO in systemic immunity. Furthermore, the proportion and activity of NK cells were greater in the spleens of the mice fed IMO than in the controls. Dietary IMO protected the mice from gamma-irradiation-induced lethality, accompanied by an inhibition of the translocation of Enterobacteriaceae. Notably, when mouse macrophage-like J774.1 cells were cultured with Lactobacillus gasseri in the presence of IMO, interleukin (IL)-12 production was greater than in the absence of IMO. These results suggest that IMO, in synergy with lactobacilli, upregulate the Th1 response and beneficially modulate host defense.

Regurgitation of bile acids from leaky bile ducts causes sclerosing cholangitis in Mdr2 (Abcb4) knockout mice

BACKGROUND & AIMS

Because the mechanisms leading to bile duct damage in sclerosing cholangitis are unknown, we aimed to determine the pathogenesis of bile duct injury in multidrug resistance gene (Mdr2) (Abcb4) knockout mice (Mdr2(-/-)) as a novel model of the disease.

METHODS

Mdr2(-/-) and wild-type controls (Mdr2(+/+)) were studied at 2, 4, and 8 weeks of age. Liver histology, ultrastructure, immunofluorescence microscopy (to study inflammatory cells, tight junction protein ZO-1, basement membrane protein laminin, fluorescence-labeled ursodeoxycholic acid), immunohistochemistry (for alpha-smooth muscle actin, nitrotyrosine), sirius red staining, bacterial cultures of intra-abdominal organs, and polymerase chain reaction (PCR) for Helicobacter bilis DNA were compared between both genotypes. Hepatic cytokine expression was determined by reverse-transcription PCR.

RESULTS

Bile ducts of Mdr2(-/-) showed disrupted tight junctions and basement membranes, bile acid leakage into portal tracts, induction of a portal inflammatory (CD11b, CD4-positive) infiltrate, and activation of proinflammatory (tumor necrosis factor [TNF]-alpha, interleukin [IL]-1beta) and profibrogenic cytokines (transforming growth factor [TGF]-beta1). This resulted in activation of periductal myofibroblasts, leading to periductal fibrosis, separating the peribiliary plexus from bile duct epithelial cells and, finally, causing atrophy and death of the bile duct epithelium. Bacterial translocation was not increased and H. bilis was not detectable in Mdr2(-/-).

CONCLUSIONS

Sclerosing cholangitis in Mdr2(-/-) mice is a multistep process with regurgitation of bile from leaky ducts into the portal tracts, leading to induction of periductal inflammation, followed by activation of periductal fibrogenesis, finally causing obliterative cholangitis owing to atrophy and death of bile duct epithelial cells.

Differential Effects of Lipopolysaccharide and Lipoteichoic Acid on the Primary Antibody Response to Keyhole Limpet Hemocyanin of Chickens Selected for High or Low Antibody Responses to Sheep Red Blood Cells

Various bacterial components are potent activators of the innate immune system and probably (in)directly determine subsequent specific immune responses. Therefore, effects of i.v. administered Salmonella enteriditis-derived lipopolysaccharide (LPS) and Staphylococcus aureus-derived lipoteichoic acid (LTA), respectively, on the primary antibody (Ab) response to keyhole limpet hemocyanin (KLH) were studied in cocks from 2 lines divergently selected for high (H line) and low (L line) Ab responses to SRBC. The Ab responses to KLH were significantly affected by a line-by-treatment-by-time interaction. Significantly higher Ab titers to KLH, S. aureus LTA, and S. enteriditis LPS were found in H line birds than in the L line birds. Ab titers to KLH were enhanced if the chickens were intravenously pretreated 24 h earlier with LTA but decreased if the chickens were intravenously pretreated 24 h earlier with LPS. Ab responses to S. enteriditis LPS were significantly enhanced when birds were immunized with KLH or pretreated with S. aureus LTA. Ab responses to S. aureus LTA were also significantly enhanced when birds were immunized with KLH or pretreated with LTA and subsequently immunized with KLH. Our findings suggest that LTA and LPS have immunomodulatory features in chickens, albeit in opposite directions. In addition, KLH acted in an immunomodulatory role too. Possible mechanisms underlying our observations and the role of LTA and LPS in polarization of the specific immune response in chickens are discussed.

A study of gut immunity to enteral endotoxin in rats of different ages: a possible cause for necrotizing enterocolitis

PURPOSE

Immature gut immunity can be a predisposing factor for necrotizing enterocolitis (NEC). The gut active immunity and innate defense to the Escherichia coli endotoxin lipopolysaccharide (LPS) in immature and mature rats were studied.

METHODS

LPS, started at a dose of 10 mg/kg, was instilled into the stomachs of fetal, newborn, 1-month and 3-month-old rats. Boost doses and normal saline control instillations were given on day 14. Rats that died after instillation had detailed postmortem examinations. For survivors, a group of 6 immunized and 6 controls were killed on day 7 for the collection of serum, spleens, mesenteric lymph nodes, and small intestines. Lymphocytes (10(6)) prepared from each tissue sample of individual group were cultured for 5 days. Serum and supernatant were analyzed for IgA and anti-E coli IgA levels.

RESULTS

All control rats survived. The doses of LPS given were 10, 5, 2.5, and 1.25 mg/kg. All fetal rats died after LPS instillation. Half-lethal dose for newborns was 2.5 mg/kg. One-month and 3-month-old rats survived all doses of LPS. The cause of death was endotoxemia. The serum IgA and total supernatant anti- E coli IgA levels of rats of all ages studied showed no significant difference.

CONCLUSION

The poor innate gut defense, not so much the active immunity, may provide an explanation for the susceptibility of the premature babies and newborn infants to the development of NEC.

Bacterial translocation: effects of artificial feeding

The most striking observation when reviewing recent literature in the field of bacterial translocation in the intestine is the small number of publications involving human subjects. Although there are some excellent reviews in this field published during the last 2 years, all experimental contributions come from animal experiments. It is therefore crucial to evaluate how valid the animal models are for human pathophysiology. Studies focusing on translocation as a major pathogenic mechanism are urgently needed to help clinicians to make correct decisions concerning protection of the gut and decide upon nutrition in the intensive care unit.

Gut-derived bone infection in the neonatal rat

The risk of osteomyelitis is increased in the premature and critically ill neonate. Although potential sites of bacterial entry are present in many of these infants, the source of infection frequently cannot be established. This study was performed to assess the possible role of bacterial translocation from the intestine in the origin of bone infection using models of breast-fed and formula-fed rat pups. Newborn Sprague-Dawley rats suckled either ad libitum by the dam (n = 30), or were fed a rat milk-simulated formula (n = 30). After 3 d, the animals were killed, and the left femur, heart blood, mesenteric lymph nodes, liver, spleen, and terminal ileum were excised. Organs were analyzed for bacteria by standard microbiologic procedures. Bacterial translocation occurred in 23% of breast-fed rats; the bone was not infected in any of these animals. After feeding of formula diet, bacterial counts of the ileum were markedly elevated (p < 0.001), and the composition of the gut flora was disrupted. Bacterial translocation was noted in all formula-fed rats. Bone cultures were positive in 23 of 30 (77%) rats after formula-feeding (p < 0.001 versus breast-feeding). Organisms translocated to the bone included Enterococci, Proteus, Enterobacter, and Escherichia coli. Bacterial species cultured from the bone correlated with the individual colonization pattern of other extraintestinal organs and with the composition of the ileal flora. Members of the gut flora can escape the intestine and colonize the bone in formula-fed rats. The gut should be considered as a potential source for osteomyelitis in the neonate.