Total parenteral nutrition adversely affects gut barrier function in neonatal piglets

Sepsis is the most common morbidity in preterm infants, who often receive total parenteral nutrition (TPN). We hypothesized that gut barrier function is compromised in TPN-fed compared with enterally fed newborn piglets (ENT pigs). Colostrum-deprived newborn pigs were implanted with jugular venous and bladder catheters under general anesthesia. Pigs were either administered TPN (n = 15) or fed formula (ENT pigs, n = 15). After 6 days, pigs were gavaged a solution of mannitol, lactulose, and polyethylene glycol 4000 (PEG 4000) and urine was collected for 24 h. At 7 days, small bowel samples were assayed for myeloperoxidase activity, morphometry, and tight junction protein abundance. Intestinal contents and peripheral organ sites were cultured for bacteria. Urinary recovery (%dose) of mannitol (53 vs. 68) was lower, whereas that of lactulose (2.93 vs. 0.18) and PEG 4000 (12.78 vs. 0.96) were higher in TPN vs. ENT pigs, respectively (P < 0.05). Incidence of translocation was similar in TPN and ENT pigs. Myeloperoxidase activity was increased in TPN vs. ENT pigs in the jejunum (P < 0.001) and was weakly correlated with lactulose (R2 = 0.32) and PEG 4000 (R2 = 0.38) recovery. Goblet cell counts did not change, but intraepithelial lymphocyte numbers decreased with TPN. Only claudin-1 protein abundance was increased in the TPN group. We conclude that TPN is associated with impairment of neonatal gut barrier function as measured by permeability but not translocation.     

GLP-2 stimulates intestinal growth in premature TPN-fed pigs by suppressing proteolysis and apoptosis

We wished to determine whether exogenous glucagon-like peptide (GLP)-2 infusion stimulates intestinal growth in parenterally fed immature pigs. Piglets (106-108 days gestation) were given parenteral nutrient infusion (TPN), TPN + human GLP-2 (25 nmol. kg(-1). day(-1)), or sow's milk enterally (ENT) for 6 days. Intestinal protein synthesis was then measured in vivo after a bolus dose of [1-(13)C]phenylalanine, and degradation was calculated from the difference between protein accretion and synthesis. Crypt cell proliferation and apoptosis were measured in situ by 5-bromodeoxyuridine (BrdU) and terminal dUTP nick-end labeling (TUNEL), respectively. Intestinal protein and DNA accretion rates and villus heights were similar in GLP-2 and ENT pigs, and both were higher (P < 0.05) than in TPN pigs. GLP-2 decreased fractional protein degradation rate, whereas ENT increased fractional protein synthesis rate compared with TPN pigs. Percentage of TUNEL-positive cells in GLP-2 and ENT groups was 48 and 64% lower, respectively, than in TPN group (P < 0.05). However, ENT, but not GLP-2, increased percentage of BrdU-positive crypt cells above that in TPN piglets. We conclude that GLP-2 increases intestinal growth in premature, TPN-fed pigs by decreasing proteolysis and apoptosis, whereas enteral nutrition acts via increased protein synthesis and cell proliferation and decreased apoptosis.     

Glucagon-like peptide-2 protects against TPN-induced intestinal hexose malabsorption in enterally refed piglets

Premature infants receiving chronic total parenteral nutrition (TPN) due to feeding intolerance develop intestinal atrophy and reduced nutrient absorption. Although providing the intestinal trophic hormone glucagon-like peptide-2 (GLP-2) during chronic TPN improves intestinal growth and morphology, it is uncertain whether GLP-2 enhances absorptive function. We placed catheters in the carotid artery, jugular and portal veins, duodenum, and a portal vein flow probe in piglets before providing either enteral formula (ENT), TPN or a coinfusion of TPN plus GLP-2 for 6 days. On postoperative day 7, all piglets were fed enterally and digestive functions were evaluated in vivo using dual infusion of enteral ((13)C) and intravenous ((2)H) glucose, in vitro by measuring mucosal lactase activity and rates of apical glucose transport, and by assessing the abundances of sodium glucose transporter-1 (SGLT-1) and glucose transporter-2 (GLUT2). Both ENT and GLP-2 pigs had larger intestine weights, longer villi, and higher lactose digestive capacity and in vivo net glucose and galactose absorption compared with TPN alone. These endpoints were similar in ENT and GLP-2 pigs except for a lower intestinal weight and net glucose absorption in GLP-2 compared with ENT pigs. The enhanced hexose absorption in GLP-2 compared with TPN pigs corresponded with higher lactose digestive and apical glucose transport capacities, increased abundance of SGLT-1, but not GLUT-2, and lower intestinal metabolism of [(13)C]glucose to [(13)C]lactate. Our findings indicate that GLP-2 treatment during chronic TPN maintains intestinal structure and lactose digestive and hexose absorptive capacities, reduces intestinal hexose metabolism, and may facilitate the transition to enteral feeding in TPN-fed infants.     

Effects of commensal bacteria on intestinal morphology and expression of proinflammatory cytokines in the gnotobiotic pig

A germ-free neonatal pig model was established to determine the effects of bacterial colonization by different species on small intestinal morphology and proinflammatory cytokine gene expression. Two experimental groups of 16 pigs were aseptically delivered by cesarian section and allocated into 4 gnotobiotic isolators. Pigs were either maintained germ-free (GF), or were orally inoculated with either a single strain of nonpathogenic Escherichia coli (EC) or Lactobacillus fermentum (LF) or conventionalized with adult porcine feces (CV). After 13 days tissue samples were collected at 5 regions corresponding to 5%, 25%, 50%, 75%, and 95% of the small intestine (SI) length. In Experiment 2, the GF isolator became contaminated with Staphylococcus epidermidis (SE). In general, intestinal responses to bacterial colonization were similar among GF, LF, and SE pigs, and intestinal responses in EC pigs were more similar to CV pigs. Responses to bacterial colonization were most pronounced in the distal SI regions (50%-95%), suggesting that nonmicrobial factors may be more important in the proximal SI. Relative to CV pigs, the distal intestines of GF, LF, and SE pigs were characterized by long villi, shallow crypts, increased relative intestinal mass, and decreased lamina propria cellularity, whereas SI morphology was intermediate in EC pigs. Relative expression of proinflammatory cytokines interleukin-1beta (IL-1beta ) and IL-6 generally increased distally in the SI and was highest in EC and CV pigs. We observed regional variation in SI morphology and proinflammatory cytokine expression, which differed with bacterial species. This study demonstrates that bacterial species differentially affect intestinal morphology and expression of proinflammatory cytokines and suggests that neonatal bacterial colonization patterns may have long-term effects on intestinal health and development.     

Persistent epithelial dysfunction and bacterial translocation after resolution of intestinal inflammation

Epithelial secretion may play an important role in reducing bacterial colonization and translocation in intestine. If so, secretory dysfunction could result in increased susceptibility to infection and inflammation. We investigated whether long-term colonic secretory dysfunction occurs after a bout of colitis and if this is accompanied by an increase in bacterial colonization and translocation. Rats were studied 6 wk after induction of colitis with trinitrobenzene sulfonic acid when inflammation had completely resolved, and epithelial permeability was normal. Intestinal loops were stimulated with either Clostridium difficile toxin A or a phosphodiesterase inhibitor. In vitro, colonic tissue from previously sensitized rats was exposed to antigen (ovalbumin). Secretory responses to all three stimuli were suppressed in rats that had previously had colitis. These rats exhibited increased (16-fold) numbers of colonic aerobic bacteria and increased (>3-fold) bacterial translocation, similar to results in rats studied after resolution of enteritis. Postcolitis bacterial translocation was prevented by daily treatment with an inhibitor of inducible nitric oxide synthase. This study demonstrates that intestinal inflammation results in prolonged impairment of colonic epithelial secretion, which may contribute to increases in bacterial load and bacterial translocation. Epithelial dysfunction of this type could underlie an increased propensity for further bouts of inflammation, a hallmark of diseases such as inflammatory bowel disease.     

大承气汤对MODS时肠道细菌微生态学影响的实验研究

目的探讨多器官功能不全综合征(MODS)大鼠肠道细菌微生态的变化及其与肠源性内毒素血症和细菌易位的关系,并观察大承气汤的影响。方法32只SD大鼠随机分成4组,对照组、模型组、大承气组和氨苄青霉素组。腹腔注射无菌酵母多糖A制备大鼠MODS模型。各组动物于造模后48 h无菌操作抽取外周静脉血和门静脉血进行内毒素含量测定;取肠系膜淋巴结进行细菌定量培养,取回肠和盲肠内容物进行肠腔内游离内毒素测定;取盲肠内容物进行肠道细菌微生态学分析。结果模型组外周血和门静脉血内毒素水平以及肠腔内游离内毒素含量均明显高于对照组(P<0.05);与对照组相比,模型组肠道菌群出现明显变化。肠球菌、肠杆菌数量明显增加,而双歧杆菌和乳酸杆菌数量出现显著下降,类杆菌数量亦出现明显下降(P<0.05)。模型组厌氧菌总数明显下降而需氧菌总数明显增加,同时厌氧菌总数/需氧菌总数的比值和B/E比值呈相应下降,发生倒置(P<0.05);正常对照组未发现肠道细菌向肠系膜淋巴结的易位,而模型组细菌易位阳性率是83.33%(P<0.05)。与模型组相比,大承气汤组上述各指标均出现明显变化(P<0.05);抗生素组作用不明显(P>0.05)。结论MODS时大鼠肠道细菌微生态出现明显变化,发生肠源性内毒素血症和细菌易位。大承气汤可以调整肠道菌群,恢复肠道微生态平衡,增加机体定植抗力,防治细菌易位和内毒素血症。     

The intestinal microflora during the first weeks of life

Bacterial colonization of the neonatal gastrointestinal tract begins during birth when the neonate comes into contact with the maternal cervical and vaginal flora. In infants delivered by Caesarean section, bacteria colonizing the neonate gastrointestinal tract are provided by the environment. The first bacteria encountered in the majority of healthy infants, are facultative anaerobes, which remain predominant during the first 2 weeks of life. Among them, Staphylococcus, Enterobacteriaceae and Streptococcus were the genera most commonly isolated from the newborn faecal flora at birth. Facultative anaerobic bacteria are followed closely by Bifidobacterium sp. Clostridium perfringens is present within 2 days with an increase incidence in newborns delivered by a Caesarean section. Clostridium perfringens seems to be the precursor for installation of other anaerobic putrefactive bacteria, as Bacteroides and other Clostridium sp. The impact of Caesarean section and the period and quality of hospitalization are mainly implicated in changes of the normal newborn flora. Feeding seems to modulate the colonization pattern. In humans, breast milk plays a role in passive immunization of the neonatal intestine, and contains factors that promote the growth of Bifidobacterium bifidum in the intestinal flora. Formula feeding seems to promote implantation and persistence of Clostridium perfringens, and clearly enhances intestinal colonization of C. difficile in newborns.     

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 G?teborg, 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.     

Enteral feeding induces diet-dependent mucosal dysfunction, bacterial proliferation, and necrotizing enterocolitis in preterm pigs on parenteral nutrition

Preterm neonates have an immature gut and metabolism and may benefit from total parenteral nutrition (TPN) before enteral food is introduced. Conversely, delayed enteral feeding may inhibit gut maturation and sensitize to necrotizing enterocolitis (NEC). Intestinal mass and NEC lesions were first recorded in preterm pigs fed enterally (porcine colostrum, bovine colostrum, or formula for 20-40 h), with or without a preceding 2- to 3-day TPN period (n = 435). Mucosal mass increased during TPN and further after enteral feeding to reach an intestinal mass similar to that in enterally fed pigs without TPN (+60-80% relative to birth). NEC developed only after enteral feeding but more often after a preceding TPN period for both sow's colostrum (26 vs. 5%) and formula (62 vs. 39%, both P < 0.001, n = 43-170). Further studies in 3-day-old TPN pigs fed enterally showed that formula feeding decreased villus height and nutrient digestive capacity and increased luminal lactic acid and NEC lesions, compared with colostrum (bovine or porcine, P < 0.05). Mucosal microbial diversity increased with enteral feeding, and Clostridium perfringens density was related to NEC severity. Formula feeding decreased plasma arginine, citrulline, ornithine, and tissue antioxidants, whereas tissue nitric oxide synthetase and gut permeability increased, relative to colostrum (all P < 0.05). In conclusion, enteral feeding is associated with gut dysfunction, microbial imbalance, and NEC in preterm pigs, especially in pigs fed formula after TPN. Conversely, colostrum milk diets improve gut maturation and NEC resistance in preterm pigs subjected to a few days of TPN after birth.     

Effect of various antibiotics on gastrointestinal colonization and dissemination by Candida albicans

Mice were treated orally with various antibiotics to determine which members of the indigenous intestinal microflora normally suppress Candida albicans colonization and dissemination from the gastrointestinal (GI) tract. The mice were given penicillin, clindamycin, vancomycin, erythromycin, or gentamicin for 3 days, and then challenged orally with C. albicans. Penicillin, clindamycin, and vancomycin, but not gentamicin or erythromycin, decreased the total anaerobic bacterial populations in the animals ceca, and increased the enteric bacilli population levels. All three of the former antibiotics allowed C. albicans to proliferate in the gut and, subsequently, disseminate from the GI tract to visceral organs. The ability of C. albicans to associate with intestinal mucosal surfaces was also tested. It was found that antibiotics which reduced anaerobic population levels, but not enteric bacilli or aerobes, also predisposed animals to mucosal association by C. albicans. It is suggested that the strictly anaerobic bacterial populations which predominate in the gut ecosystem are responsible for the inhibition of C. albicans adhesion, colonization and dissemination from the GI tract.     

Enteral bile acid treatment improves parenteral nutrition-related liver disease and intestinal mucosal atrophy in neonatal pigs

Total parenteral nutrition (TPN) is essential for patients with impaired gut function but leads to parenteral nutrition-associated liver disease (PNALD). TPN disrupts the normal enterohepatic circulation of bile acids, and we hypothesized that it would decrease intestinal expression of the newly described metabolic hormone fibroblast growth factor-19 (FGF19) and also glucagon-like peptides-1 and -2 (GLP-1 and GLP-2). We tested the effects of restoring bile acids by treating a neonatal piglet PNALD model with chenodeoxycholic acid (CDCA). Neonatal pigs received enteral feeding (EN), TPN, or TPN + CDCA for 14 days, and responses were assessed by serum markers, histology, and levels of key regulatory peptides. Cholestasis and steatosis were demonstrated in the TPN group relative to EN controls by elevated levels of serum total and direct bilirubin and also bile acids and liver triglyceride (TG) content. CDCA treatment improved direct bilirubin levels by almost fourfold compared with the TPN group and also normalized serum bile acids and liver TG. FGF19, GLP-1, and GLP-2 were decreased in plasma of the TPN group compared with the EN group but were all induced by CDCA treatment. Intestinal mucosal growth marked by weight and villus/crypt ratio was significantly reduced in the TPN group compared with the EN group, and CDCA treatment increased both parameters. These results suggest that decreased circulating FGF19 during TPN may contribute to PNALD. Moreover, we show that enteral CDCA not only resolves PNALD but acts as a potent intestinal trophic agent and secretagogue for GLP-2.     

New generation lipid emulsions prevent PNALD in chronic parenterally fed preterm pigs

Total parenteral nutrition (TPN) is associated with the development of parenteral nutrition-associated liver disease (PNALD) in infants. Fish oil-based lipid emulsions can reverse PNALD, yet it is unknown if they can prevent PNALD. We studied preterm pigs administered TPN for 14 days with either 100% soybean oil (IL), 100% fish oil (OV), or a mixture of soybean oil, medium chain triglycerides (MCTs), olive oil, and fish oil (SL); a group was fed formula enterally (ENT). In TPN-fed pigs, serum direct bilirubin, gamma glutamyl transferase (GGT), and plasma bile acids increased after the 14 day treatment but were highest in IL pigs. All TPN pigs had suppressed hepatic expression of farnesoid X receptor (FXR), cholesterol 7-hydroxylase (CYP7A1), and plasma 7α-hydroxy-4-cholesten-3-one (C4) concentrations, yet hepatic CYP7A1 protein abundance was increased only in the IL versus ENT group. Organic solute transporter alpha (OSTα) gene expression was the highest in the IL group and paralleled plasma bile acid levels. In cultured hepatocytes, bile acid-induced bile salt export pump (BSEP) expression was inhibited by phytosterol treatment. We show that TPN-fed pigs given soybean oil developed cholestasis and steatosis that was prevented with both OV and SL emulsions. Due to the presence of phytosterols in the SL emulsion, the differences in cholestasis and liver injury among lipid emulsion groups in vivo were weakly correlated with plasma and hepatic phytosterol content.     

凝结芽胞杆菌活菌片对实验性腹泻小鼠的治疗作用

目的 观察凝结芽胞杆菌活菌片对氨苄青霉素钠诱发的小鼠腹泻的治疗作用。方法利用氨苄青霉素钠口服诱发小鼠实验性腹泻和肠道菌群失调,然后用凝结芽胞杆菌活菌片,口服,每天2次,共4d,观察治疗后的小鼠排便和肠道菌群变化。结果在各给药组中,治疗第1天有70％～85％的小鼠排正常便,生理盐水组只有10％排正常便（P〈0．01）;治疗第2天给药组中有80％～90％的小鼠排正常便,生理盐水组仅为50％（P〈0．01）。肠道菌群分析结果表明,凝结芽胞杆菌在治疗第2天开始定植,停药第7天后逐渐消失,定植期为10d左右。在各给药组中,治疗第2天肠道菌群开始恢复,第4天均升高到正常,而生理盐水组的恢复比各给药组显著的慢（P〈0．01）。结论 凝结芽胞杆菌活菌片对小鼠实验性腹泻有明显的止泻作用,并能加速肠道菌群的恢复。     

Rye Affects Bacterial Translocation,Intestinal Viscosity,Microbiota Composition and Bone Mineralization in Turkey Poults

Previously, we have reported that rye significantly increased both viscosity and Clostridium perfringens proliferation when compared with corn in an in vitro digestive model. Two independent trials were conducted to evaluate the effect of rye as a source of energy on bacterial translocation, intestinal viscosity, gut microbiota composition, and bone mineralization, when compared with corn in turkey poults. In each experiment, day-of-hatch, turkey poults were randomly assigned to either a corn or a rye diet (n = 0 /group). At 10 d of age, in both experiments, 12 birds/group were given an oral gavage dose of fluorescein isothiocyanate dextran (FITC-d). After 2.5 h of oral gavage, blood and liver samples were collected to evaluate the passage of FITC-d and bacterial translocation (BT) respectively. Duodenum, ileum and cecum gut sections were collected to evaluate intestinal viscosity and to enumerate gut microbiota. Tibias were collected for observation of bone parameters. Broilers fed with a rye diet showed increased (p<0.05) intestinal viscosity, BT, and serum FITC-d. Bacterial enumeration revealed that turkey poults fed with rye had increased the number of total lactic acid bacteria (LAB) in all three sections of the gastrointestinal tract evaluated when compared to turkey poults fed with corn. Turkey poults fed with rye also had significantly higher coliforms in duodenum and ileum but not in the ceca, whereas the total number of anaerobes increased only in duodenum. A significant reduction in bone strength and bone mineralization was observed in turkey poults fed with rye when compared with corn fed turkey poults. In conclusion, rye evoked mucosal damage in turkey poults that increased intestinal viscosity, increased leakage through the intestinal tract, and altered the microbiota composition and bone mineralization. Studies to evaluate dietary inclusion of selected Direct-Fed Microbial (DFM) candidates that produce exogenous enzymes in rye fed turkey poults are currently being evaluated.     

Assessment of mouse strain on bacterial translocation from the gastrointestinal tract

The translocation of indigenous bacteria from the gastrointestinal tract to the mesenteric lymphnodes was compared in ten strains of mice. Indigenous Escherichia coli were cultured from the mesenteric lymphnodes of only two of the six mouse strains examined. Thus, spontaneous translocation of indigenous enteric bacteria across the intestinal barrier did not occur to any significant extent in any of the mouse strains examined. Since bacterial overgrowth in the gastrointestinal tract promotes bacterial translocation, bacterial translocation was tested in ten mouse strains including B10 series after antibiotic-decontaminated and subsequent colonization with streptomycin-resistant E. coli C25. E. coli C25 populated the ceca of the mice at levels of 10(8) to 10(9) per gram and translocated to 90-100% of the mesenteric lymphnodes with mean of 10(1.13) to 10(1.86) per mesenteric lymphnode. However, there were no significant differences between mouse strains as to the translocation incidence or the numbers of viable E. coli C25 per mesenteric lymphnode. Thus, genetic differences between mouse strains did not influence bacterial translocation from the gastrointestinal tract to the mesenteric lymphnodes.     

Gut-associated lymphoid T cell suppression enhances bacterial translocation in alcohol and burn injury

The mechanism of alcohol-mediated increased infection in burn patients remains unknown. With the use of a rat model of acute alcohol and burn injury, the present study ascertained whether acute alcohol exposure before thermal injury enhances gut bacterial translocation. On day 2 postinjury, we found a severalfold increase in gut bacterial translocation in rats receiving both alcohol and burn injury compared with the animals receiving either injury alone. Whereas there were no demonstrable changes in intestinal morphology in any group of animals, a significant increase in intestinal permeability was observed in ethanol- and burn-injured rats compared with the rats receiving either injury alone. We further examined the role of intestinal immune defense by determining the gut-associated lymphoid (Peyer's patches and mesenteric lymph nodes) T cell effector responses 2 days after alcohol and burn injury. Although there was a decrease in the proliferation and interferon-gamma by gut lymphoid T cells after burn injury alone; the suppression was maximum in the group of rats receiving both alcohol and burn injuries. Furthermore, the depletion of CD3(+) cells in healthy rats resulted in bacterial accumulation in mesenteric lymph nodes; such CD3(+) cell depletion in alcohol- and burn-injured rats furthered the spread of bacteria to spleen and circulation. In conclusion, our data suggest that the increased intestinal permeability and a suppression of intestinal immune defense in rats receiving alcohol and burn injury may cause an increase in bacterial translocation and their spread to extraintestinal sites.     

Colonization and distribution of segmented filamentous bacteria (SFB) in chicken gastrointestinal tract and their relationship with host immunity

Uncultivable segmented filamentous bacteria (SFB) reside in the gastrointestinal (GI) tract of mammals and can boost the host immunity. Immunoglobulin A (IgA) from mother's milk has been previously shown to be a key factor in regulating SFB colonization. Because neonatal chicken cannot acquire IgA from maternal milk, they are a good model to examine the role of IgA in SFB colonization. Here, we used the fluorescent in situ hybridization (FISH) and quantitative PCR (qPCR) to monitor the colonization and distribution of SFB in chickens aged from 2-day-old to 6-week-old. Early SFB colonization, which primarily occurred in the ileal mucosa (< 13 days old), was IgA independent. From the age of 17-42 days, there was an increase in IgA in the gut mucosa, which was correlated with a decrease in SFB. To examine the effect of probiotics and immunosuppression on SFB colonization, we treated the chickens by feeding them Lactobacillus delbrueckii or giving them a subcutaneous injection of cyclophosphamide (CTX). Feeding lactobacilli at birth rendered SFB colonization occurring 4 days earlier, while CTX treatment increases the SFB colonization through reducing the other non-SFB bacteria. Altogether, our data suggest that early colonization of SFB in chicken occurs independently of IgA and the population of SFB in the GI tract of chicken may be manipulated from birth via probiotic or CTX treatment.     

Elective cesarean delivery affects gut maturation and delays microbial colonization but does not increase necrotizing enterocolitis in preterm pigs

Although preterm birth and formula feeding increase the risk of necrotizing enterocolitis (NEC), the influences of cesarean section (CS) and vaginal delivery (VD) are unknown. Therefore, gut characteristics and NEC incidence and severity were evaluated in preterm pigs (92% gestation) delivered by CS or VD. An initial study showed that newborn CS pigs (n = 6) had decreased gastric acid secretion, absorption of intact proteins, activity of brush-border enzymes and pancreatic hydrolases, plasma cortisol, rectal temperature, and changes in blood chemistry, indicating impaired respiratory function, compared with VD littermates (n = 6). In a second experiment, preterm CS (n = 16) and VD (n = 16) pigs were given total parenteral nutrition (36 h) then fed porcine colostrum (VD-COL, n = 6; CS-COL, n = 6) or infant milk formula (VD-FORM, n = 10; CS-FORM, n = 10) for 2 days. Across delivery, FORM pigs showed significantly higher NEC incidence, tissue proinflammatory cytokines (IFN-gamma and IL-6), Clostridium colonization, and impaired intestinal function, compared with COL pigs. NEC incidence was equal for CS (6/16) and VD (6/16) pigs, CS pigs had decreased bacterial diversity and density, higher villus heights, and increased brush-border enzyme activities (lactase, aminopeptidases) compared with VD pigs. In particular, VD-FORM pigs showed reduced mucosal proportions, reduced lactase and aminopeptidases, and increased proinflammatory cytokine IL-6 compared with CS-FORM (P < 0.06). Despite the initial improvement of intestinal and metabolic functions following VD, gut function, and inflammation were similar, or more negatively affected in VD neonates than CS neonates. Both delivery modes exhibited positive and negative influences on the preterm gut, which may explain the similar NEC incidence.     

抗生素所致腹泻大鼠肠屏障功能损伤及乳酸杆菌保护机制的研究

目的探讨抗生素对所致腹泻大鼠肠道屏障功能、肠道菌群结构和肠道细菌移位的影响及乳酸杆菌制剂的保护机制。方法采用细菌培养法动态测定抗生素所致腹泻大鼠肠道菌群变化及肠系膜淋巴结、肝脏、脾脏和结肠组织的移位细菌量;应用光镜和电子显微镜观察肠黏膜组织超微结构变化。结果应用抗生素可致大鼠腹泻,肠道菌群失调,肠黏膜组织受损,发生肠道细菌移位。大肠埃希菌攻击可加重肠道菌群失调和肠黏膜损伤程度,促发细菌移位发生。乳酸杆菌可扶正肠菌群结构,修复损伤的肠黏膜,抑制肠细菌移位发生。结论阐明了抗生素、肠黏膜屏障功能、肠道菌群结构和肠道细菌移位间的互为因果,相互影响的关系。微生态制剂在维持机体微生态平衡、修复肠黏膜方面具有保护作用。     

Green Fluorescent Protein Labeling Escherichia coli TG1 Confirms Intestinal Bacterial Translocation in a Rat Model of Chemotherapy

It has been reported that treatment with methotrexate (MTX) induces intestinal bacterial translocation; however, the definitive evidence of intestinal bacterial translocation induced by MTX has been lacking. The aim of this study was to confirm the intestinal bacterial translocation caused by MTX and to evaluate the preventive effect of granulocyte colony-stimulating factor (G-CSF) on intestinal bacterial translocation caused by MTX. Sprague-Dawley rats were treated with MTX (3.5 mg/kg) for 3 days to induce intestinal bacterial translocation; with gavaged Escherichia coli TG1 labeled with green fluorescent protein (GFP) for 2 days to track intestinal bacterial translocation; and with G-CSF (10 μg/kg) for 4 days to prevent intestinal bacterial translocation. Representative tissue specimens from the mesenteric lymph nodes, spleen, liver, and kidney were aseptically harvested for bacteria culture in ampicillin-supplemented medium. The bacteria labeled with GFP were detected in tissue specimens harvested from the rats treated with MTX but not detected in the rats that were not treated with MTX. G-CSF significantly ameliorated the situation of intestinal bacterial translocation.