Translocation ofLactobacillus murinus from the gastrointestinal tract

Bacterial translocation is defined as the passage of viable bacteria from the gastrointestinal tract to the mesenteric lymph nodes and other extraintestinal sites. The translocation rate of a newly described species of indigenous bacteria,Lactobacillus murinus, was compared with the translocation rates of indigenousLactobacillus acidophilus and nonindigenousSalmonella enteritidis. Groups of germfree or antibiotic-decontaminated, specific pathogen-free mice were monoassociated with each of these bacterial strains and tested at various intervals for translocation to the mesenteric lymph nodes. The translocation rates of the various bacteria expressed in decreasing order as the numbers of translocating bacteria per gram mesenteric lymph node wereS. enteritidis, L. murinus, andL. acidophilus. The degree of histologic damage to the gastrointestinal mucosa after monoassociation with these strains followed the same pattern. Thus,L. murinus translocates from the GI tract at a surprisingly high rate for an indigenous bacterial strain, and its translocation appears to be associated with mucosal alterations.     

Bacterial translocation from the intestines

Bacterial translocation is defined as the passage of viable bacteria from the gastrointestinal (GI) tract through the mucosal epithelium to other sites, such as the mesenteric lymph nodes, spleen, liver and blood. This paper reviews results from animal models utilized to obtain information concerning the defense mechanisms operating in the healthy host to confine bacteria to the GI tract. Gnotobiotic and antibiotic-decontaminated mice colonized with particular bacteria demonstrated that the indigenous GI flora maintains an ecologic equilibrium to prevent intestinal bacterial overgrowth and translocation from the GI tract. Studies with athymic (nu/nu) mice, thymus-grafted (nu/nu) mice, neonatally thymectomized mice, and mice injected with immunosuppressive agents demonstrated that the host immune system is another defense mechanism inhibiting bacterial translocation from the GI tract. Ricinoleic acid given orally to mice disrupted the intestinal epithelial barrier allowing indigenous bacteria to translocate from the GI tract. Thus, bacterial translocation from the GI tract of healthy adult mice is inhibited by: (a) an intact intestinal epithelial barrier, (b) the host immune defense system, and (c) an indigenous GI flora maintaining ecological equilibrium to prevent bacterial overgrowth. Deficiencies in host defense mechanisms act synergistically to promote bacterial translocation from the GI tract as demonstrated by animal models with multiple alterations in host defenses. Bacterial translocation occurred to a greater degree in mice with streptozotocin-induced diabetes, mice receiving nonlethal thermal injury, and mice receiving the combination of an immunosuppressive agent plus an oral antibiotic than in mice with only a primary alteration in host defenses. The study of bacterial translocation in these complex models suggests that opportunistic infections from the GI tract occur in discrete stages. In the healthy adult animal, bacterial translocation from the GI tract either does not occur or occurs at a very low level and the host immune defenses eliminate the translocating bacteria. Bacterial translocation does take place if one of the host defense mechanisms is compromised, such as a deficiency in the immune response, bacterial overgrowth in the intestines, or an increase in the permeability of the intestinal barrier. In this first stage, the bacteria usually translocate in low numbers to the mesenteric lymph node, and sometimes spleen or liver, but do not multiply and spread systemically.(ABSTRACT TRUNCATED AT 400 WORDS)     

Bacterial translocation from the gastrointestinal tracts of thymectomized mice

The incidence of translocation of viable indigenous bacteria from the gastrointestinal tract to the mesenteric lymph node, spleen, liver, and kidney was compared in neonatally thymectomized mice and sham-thymectomized specific pathogen-free mice. The immunologic responses of the thymectomized mice to sheep erythrocytes were decreased compared to the responses of sham-thymectomized mice. Strictly anaerobic bacteria were isolated from only 1.8% of the organs from thymectomized mice and from none of the organs of shamthymectomized mice. Aerobic or facultatively anaerobic bacteria were cultured from 27.4% of the organs of thymectomized mice. Of the thymectomized mice, 70.7% contained viable aerobic or facultatively anaerobic bacteria in one or more of their organs tested, compared with only 10% of the sham-thymectomized mice.Escherichia coli was the predominant bacterial species isolated from these organs, althoughStaphylococcus aureus, Streptococcus, andCorynebacterium also were present.Bacteroides were the only strictly anaerobic bacteria cultured. Neonatal thymectomy promotes the translocation of certain indigenous bacteria from the gastrointestinal tract to the mesenteric lymph node, spleen, liver, and kidney.     

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.     

Bacterial translocation can increase plasma corticosterone and brain catecholamine and indoleamine metabolism

The potential contribution of stress-induced bacterial translocation to the activation of the hypothalamo-pituitary-adrenocortical (HPA) axis and brain biogenic amines was assessed. Mice were restrained for various periods, and brain concentrations of tryptophan, catecholamines, serotonin, and their metabolites, plasma corticosterone, and the translocation of viable bacteria from the gastrointestinal tract to the mesenteric lymph nodes, spleen, and liver were measured. Restraint induced the translocation of indigenous gram-positive bacteria in only a small proportion of animals, but translocation of gram-negative bacteria did not occur. Restraint induced short-lived increases in plasma corticosterone and brain amine metabolism, whereas bacterial translocation was slower and persisted long after the HPA axis and neurochemical responses had dissipated. When mice were infected with Salmonella typhimurium, spontaneous translocation occurred and plasma corticosterone, interleukin-6 concentrations, and brain catecholamine and indoleamine metabolism were elevated. These findings indicate that the translocation of indigenous gastrointestinal bacteria did not contribute to the HPA axis and neurochemical changes induced by restraint. However, translocation of nonindigenous S. typhimurium with or without restraint did induce HPA and neurochemical responses.     

Inhibition of Bacterial Translocation from the Gastrointestinal Tract of Mice Injected with Cyclophosphamide

Effects of intraperitoneal injection of cyclophosphamide, an immunosuppressant, on the degree of bacterial translocation and morphological changes of Peyer's patches (PP) in the intestine were investigated with antibiotic-decontaminated SPF mice and germfree mice monoassociated with Escherichia coli C25. It has been reported that treatment with cyclophosphamide induces bacterial translocation. Cyclophosphamide treatment in this study, however, significantly decreased E. coli C25 translocation from the gastrointestinal tract to the mesenteric lymph nodes (MLN), although the numbers of lymphoid cells, especially B cells, in the PP, MLN, and spleen were remarkably reduced. Four injections of cyclophosphamide at a dose of 100 mg/kg inhibited bacterial translocation more than one injection at a dose of 200 mg/kg in SPF mice. Germfree mice, however, treated with one dose of 200 mg/kg showed the same inhibition of bacterial translocation as those given 100 mg/kg four times. In cyclophosphamide-treated mice, lymph follicles in the PP were obviously smaller than those in control mice, M-cells were similar in appearance to absorption epithelial cells except for short microvilli, and immune cells among the M-cells had disappeared. These data suggested that inhibition of bacterial translocation in mice treated with cyclophosphamide may be the result of morphological and physiological changes of epithelial cells in the gastrointestinal tract, especially M-cells, as a point of entry of invading bacteria, independent of the changes in immunological function. Received: 16 November 1995 / Accepted: 12 December 1995     

The analysis of the defense mechanism against indigenous bacterial translocation in X-irradiated mice

The defense mechanism against indigenous bacterial translocation was studied using a model of endogenous infection in X-irradiated mice. All mice irradiated with 9 Gy died from day 8 to day 15 after irradiation. The death of mice was observed in parallel with the appearance of bacteria from day 7 in various organs, and the causative agent was identified to be Escherichia coli, an indigenous bacterium translocating from the intestine. Decrease in the number of blood leukocytes, peritoneal cells and lymphocytes in Peyer's patches or mesenteric lymph nodes was observed as early as 1 day after irradiation with 6 or 9 Gy. The mitogenic response of lymphocytes from various lymphoid tissues was severely affected as well. The impairment of these parameters for host defense reached the peak 3 days after irradiation and there was no recovery. However, in vivo bactericidal activity of Kupffer cells in mice irradiated with 9 Gy was maintained in a normal level for a longer period. It was suggested that Kupffer cells play an important role in the defense against indigenous bacteria translocating from the intestine in mice.     

Indigenous bacteria and bacterial metabolic products in the gastrointestinal tract of broiler chickens

The gastrointestinal tract is a dynamic ecosystem containing a complex microbial community. In this paper, the indigenous intestinal bacteria and the microbial fermentation profile particularly short chain fatty acids (SCFA), lactate, and ammonia concentrations are reviewed. The intestinal bacterial composition changes with age. The bacterial density of the small intestine increases with age and comprises of lactobacilli, streptococci, enterobacteria, fusobacteria and eubacteria. Strict anaerobes (anaerobic gram-positive cocci, Eubacterium spp., Clostridium spp., Lactobacillus spp., Fusobacterium spp. and Bacteroides) are predominating caecal bacteria in young broilers. Data from culture-based studies showed that bifidobacteria could not be isolated from young birds, but were recovered from four-week-old broilers. Caecal lactobacilli accounted for 1.5-24% of the caecal bacteria. Gene sequencing of caecal DNA extracts showed that the majority of bacteria belonged to Clostridiaceae. Intestinal bacterial community is influenced by the dietary ingredients, nutrient levels and physical structure of feed. SCFA and other metabolic products are affected by diet formulation and age. Additional studies are required to know the bacterial metabolic activities together with the community analysis of the intestinal bacteria. Feed composition and processing have great potential to influence the activities of intestinal bacteria towards a desired direction in order to support animal health, well-being and microbial safety of broiler meat.     

Bacterial translocation from the gastrointestinal tracts of mice receiving immunosuppressive chemotherapeutic agents

Specific pathogen-free (SPF) mice were treated with certain classes of immunosuppressive chemotherapeutic agents to determine if they would promote bacterial translocation from the gastrointestinal tract to the mesenteric lymph node, spleen, or liver. The antimetabolites methotrexate, 5-fluorouracil, and cytosine arabinoside were injected once intraperitoneally into SPF mice, and the mice were tested for bacterial translocation from the gastrointestinal tract. When total organs from the treated mice were compared with the total organs from the control mice, the alkylating agent cyclophosphamide promoted bacterial translocation when injected once intraperitoneally at doses of 100–400 mg/kg. Increasing the number of injections of cyclophosphamide did not increase the incidence of bacterial translocation. The steroid prednisone also promoted bacterial translocation after one intraperitoneal injection of 10–150 mg/kg. Prednisone and cyclophosphamide at various doses appeared to be more effective in promoting bacterial translocation from the gastrointestinal tract than the antimetabolites. The aerobic and facultatively anaerobic bacteria translocating to the various organs were identified asLactobacillus acidophilus, Escherichia coli, Klebsiella pneumoniae, Streptococcus faecalis, Staphylococcus aureus, andProteus mirabilis. Groups of SPF mice also were injected once intraperitoneally with the minimal dose of each chemotherapeutic drug that induced bacterial translocation, and then tested for immune responsiveness toE. coli vaccination. Each of the chemotherapeutic agents at the minimal doses promoting bacterial translocation also suppressed the serum antibody responses to antigens of indigenousE. coli. However, other toxic manifestations of these chemotherapeutic agents also may be involved in promoting bacterial translocation. The promotion of bacterial translocation from the gastrointestinal tract by these chemotherapeutic agents has important implications for the pathogenesis of infectious disease in patients receiving these drugs.     

Orally administered bovine lactoferrin inhibits bacterial translocation in mice fed bovine milk.

Feeding of bovine milk to mice induced a high incidence of bacterial translocation from the intestines to the mesenteric lymph nodes, and the bacteria involved were mainly members of the family Enterobacteriaceae. Supplementation of the milk diet with bovine lactoferrin or a pepsin-generated hydrolysate of bovine lactoferrin resulted in significant suppression of bacterial translocation. Our findings suggest that this ability of lactoferrin to inhibit bacterial translocation may be due to its suppression of bacterial overgrowth in the guts of milk-fed mice.     

Studies on pathogenicity of Yersinia enterocolitica in mice with diabetes mellitus

In this study, we investigated the colonizing ability as well as the association of Yersinia enterocolitica serotype 0:9 to epithelial cells of the intestinal tract, Peyer's patches, mesenteric lymph nodes, liver, spleen and lungs in Alloxan-induced diabetes mellitus in mice and controls. The results showed that: (a) in diabetic mice the Y. enterocolitica colonizing values were in range of 10(6.5)-10(8.25) CFU/g of feces; (b) maximum colonizing values were found in distal ileum and Peyer's patches and lower in colon; (c) the infection was progressive with dissemination of bacteria in the liver, spleen and lung; (d) in control (non-diabetic) mice, the colonizing values were 10-100 times lower than those found in the diabetic batch; (e) the main histopathological changes noticed, namely ileitis, mesenteric lymphadenitis and septicemia, were presumably induced by high bacterial load in the liver, spleen and lung leading to a septic course of infection as well as toxic effects of heat-stable enterotoxins of Y. enterocolitica (Yst). The results were confirmed by electron microscopy observations. Summing up, these results demonstrate that diabetic mice were more susceptible to Y. enterocolitica cells than normal mice.     

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.     

多器官功能不全综合征时肠道细菌易位及通里攻下法影响的实验研究

肠道是全身感染的起源,细菌易位在ＭＯＤＳ的发生发展中具有重要作用。本实验以放射性同位素３５Ｓ标记致病Ｅｃｏｌｉ作示踪剂,研究不同剂量酵母多糖腹腔注射所致ＭＯＤＳ时肠道细菌易位的途径和程度,并观察通里攻下中药和抗生素对细菌易位的影响。结果表明,酵母多糖腹腔注射能造成肠道屏障损伤引起细菌易位,细菌易位的程度具有剂量依赖性。细菌易位途径主要有两条,低剂量时细菌易位以肠系膜淋巴结途径为主,高剂量时以门静脉途径为主。予先应用新霉素和灭滴灵给肠道脱污染反而加重细菌易位,抗生素治疗对细菌移位效果不明显。以大承气汤为代表的通里攻下中药对控制细菌易位有显著效果     

参麦注射液对严重烫伤大鼠肠道屏障功能的保护作用

目的:探索参麦注射液对30% Ⅲ°烫伤早期肠道屏障功能的保护作用,为参麦注射液防治肠源性感染提供实验依据。方法:Wistar大鼠60只,随机分为正常对照组、模型对照组,地塞米松5 mg/kg组、参麦注射液5、10、15 mg/kg组,每组10只,使用烫伤仪建立30% Ⅲ°烫伤动物模型,立即腹腔注射相应的药物,每天1次。烫伤72 h后,检测肝脏、脾脏、肠系膜淋巴结细菌移位量、血浆内毒素、二胺氧化酶(DAO)、肿瘤坏死因子-α(TNF-α)及白细胞介素-6(IL-6)水平和肠粘膜分泌型免疫球蛋白A(sIgA)的水平。结果:与正常对照组比较,模型组肝脏、脾脏、肠系膜淋巴结细菌移位量,血浆内毒素、DAO、TNF-α及 IL-6和肠黏膜sIgA水平明显升高(P＜0.01);与模型组比较,地塞米松组和参麦注射液5、10、15 mg/kg组肝脏、脾脏、肠系膜淋巴结细菌移位量,血浆内毒素、DAO、TNF-α及 IL-6和肠黏膜sIgA水平明显降低(P＜0.05或P＜0.01)。结论:参麦注射液可减轻严重烫伤引起的肠粘膜损伤,效果与地塞米松相当,高剂量组效果更好。     

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.     

华支睾吸虫感染对大鼠肠道菌群移位和内毒素血症的影响

目的研究肠道细菌移位在华支睾吸虫病致病机制中的作用。方法建立华支睾吸虫感染大鼠模型。分别在造模后48 h(后尾蚴期)、18 d(童虫期)和35 d(成虫期),取肝、肺、淋巴结和血液组织,采用平板培养法进行细菌移位的检测;采用鲎三肽基质染色定量法检测血浆内毒素含量。结果感染18 d后,实验组肠道细菌移位率开始增高,至感染35 d时,细菌移位率为70%,明显高于对照组的10%,差异有统计学意义(P=0.0230.05);感染鼠以童虫期、成虫期细菌移位现象明显,总移位率为65%,与对照组10%比较,差异有统计学意义(u=3.59,P0.01),且在肝、肺、淋巴结和血液组织中,移位发生率分别为60%、15%、25%和10%,以肝脏部位最高;造模后18 d血浆内毒素水平明显增高,造模后35 d血浆LPS水平略有下降,但仍明显高于对照组,差异有统计学意义(t=7.612,P0.01)。结论华支睾吸虫感染可引发宿主肠道菌群移位,以肝组织多发,从而参与致病机制。     

MAdCAM-1 expressing sacral lymph node in the lymphotoxin beta-deficient mouse provides a site for immune generation following vaginal herpes simplex virus-2 infection

The members of the lymphotoxin (LT) family of molecules play a critical role in lymphoid organogenesis. Whereas LT alpha-deficient mice lack all lymph nodes and Peyer's patches, mice deficient in LT beta retain mesenteric lymph nodes and cervical lymph nodes, suggesting that an LT beta-independent pathway exists for the generation of mucosal lymph nodes. In this study, we describe the presence of a lymph node in LT beta-deficient mice responsible for draining the genital mucosa. In the majority of LT beta-deficient mice, a lymph node was found near the iliac artery, slightly misplaced from the site of the sacral lymph node in wild-type mice. The sacral lymph node of the LT beta-deficient mice, as well as that of the wild-type mice, expressed the mucosal addressin cell adhesion molecule-1 similar to the mesenteric lymph node. Following intravaginal infection with HSV type 2, activated dendritic cells capable of stimulating a Th1 response were found in this sacral lymph node. Furthermore, normal HSV-2-specific IgG responses were generated in the LT beta-deficient mice following intravaginal HSV-2 infection even in the absence of the spleen. Therefore, an LT beta-independent pathway exists for the development of a lymph node associated with the genital mucosa, and such a lymph node serves to generate potent immune responses against viral challenge.     

The immune response of male DSN hamsters to a primary infection with Ancylostoma ceylanicum

The immune response of hamsters to a chronic hookworm infection has been investigated. Ancylostoma ceylanicum caused long term infections in hamsters which were associated with prominent changes in secondary lymphoid organs. The mesenteric lymph nodes and spleens increased rapidly in size stabilizing at approximately 3-4 times the weight in control animals by weeks 3-7. Cells from both the mesenteric lymph node and spleen, after an initial period of increased blast cell activity, became less reactive in the latter stages of infection. Serum antibody responses were marked, commencing in weeks 3-4 and increasing in intensity throughout the 10 week period of measurement. The results are discussed in relation to their contribution to the understanding of human hookworm infection.     

Alteration of intestinal microbial ecology in mice by recombinant interleuken-2

In addition to its beneficial immunostimulatory properties, interleukin-2 (IL-2) has many significant side effects including gastrointestinal (GI) toxicities. Preliminary studies of the effects of IL-2 on GI bacterial translocation suggested that IL-2 altered intestinal bacterial population levels. In order to further define the effects of IL-2 on intestinal microecology, groups of specific pathogen-free C57BL/6 mice were injected subcutaneously twice daily for 5 days with various dosages of human recombinant IL-2 (up to a maximum of 1.6 mg/kg injection) or an equal volume of sterile buffer. One day after the final injections, IL-2 had significantly (P<.05) increased in a dose-dependent fashion the mean cecal population levels of indigenousEscherichia coli, other gram-negative bacilli, streptococci, and staphylococci. Maximum increases above control cecal population levels were more than 10,000-fold forE. coli and streptococci, 209-fold for gram-negative bacilli other thanE. coli, and 93-fold for staphylococci. These changes were completely reversible, with normal cecal population levels 12 days after the last IL-2 injection. IL-2 did not change the total cecal population levels of strictly anaerobic bacteria. Ileal and cecal structures, as assessed by light microscopy, were not altered by the highest dose of IL-2. When incubated in vivo with 1.6 mg/ml of IL-2, the growth of an indigenous strain ofE. coli was not different from growth in broth alone. Thus, IL-2 treatment caused the intestinal overgrowth of common opportunistic aerobic and facultatively anaerobic bacterial pathogens, without altering total population levels of strict anaerobes or affecting intestinal histology.