Dietary Curdlan Increases Proliferation of Bifidobacteria in The Cecum of Rats

Significant increases in the amounts of short-chain fatty acids and lactate, and in numbers of bifidobacteria were observed in the cecum of curdlan (CD) -fed rats as compared with those of cellulose-fed ones. The in vitro proliferation of 5 species of bifidobacteria was markedly increased in the cultures containing the supernatant obtained from the cecal contents of CD-fed rats. These findings suggest that bifidus factors have been produced in the cecum of CD-fed rats.     

Effects of dietary lactose and purified diet on intestinal microflora of rats

In the rats fed on lactose-containing purified diet (PDL), bifidobacteria remarkably increased in number in both the jejunum and cecum as compared with those fed on control diet (PD) or conventional diet (NMF). Besides, lactobacilli, streptococci, staphylococci, and Escherichia coli increased in number in the jejuna and/or ceca of rats fed on PDL as compared with those fed on PD. The incidence and numbers of Lactobacillus species were remarkably different between the rats fed on PDL and those on any of the other diets. Indole-producing Bacteroides spp. were rarely isolated from the PDL-fed rats. The cecum was markedly enlarged in the PDL rats and reduced in the PD rats as compared with that in the NMF animals.     

Impact of colostomy on intestinal microflora and bacterial translocation in young rats fed with heat-killed Lactobacillus acidophilus strain LB

A rat animal model of left colostomy was found to significantly impair the growth curve of rats. Assessment of the intestinal flora showed that colostomy mostly affects the cecal but not colonic microflora. Generally, the number of enterococci was increased in both ileum and cecum; cecal lactobacilli also rose, accounting for a promotion of lactic acid bacteria in colostomised rats. No significant differences between colostomised, laparotomised and control rats could be observed for the translocation of intestinal bacteria to internal organs of rats (i.e. spleen, kidneys, lungs or liver), whatever their diet. Heat-killed Lactobacillus acidophilus strain LB administration (dead probiotic bacteria) tended to exhibit a stimulatory effect on bifidobacteria, probably affecting the culture-medium fermentation substances included in the pharmaceutical product. This effect was abolished by laparotomy and colostomy. A trend towards a probiotic-like effect, not susceptible to colostomy, was also witnessed as counts of lactobacilli tended to increase in both cecum and colon of all animals fed with L. acidophilus LB.     

Comparative study of bacterial groups within the human cecal and fecal microbiota

The composition of the human cecal microbiota is poorly known because of sampling difficulties. Samples of cecal fluid from eight subjects were collected via an intestinal tube. Feces were also collected. Total anaerobes, facultative anaerobes, bifidobacteria, and Bacteroides were enumerated by culture methods, and the predominant phylogenetic groups were quantified by molecular hybridization using a set of six rRNA-targeted probes. The numbers of strict anaerobes, bifidobacteria, Bacteroides, and members of the Clostridium coccoides group and Clostridium leptum subgroup were lower in the cecum. Facultative anaerobes represented 25% of total bacteria in the cecum versus 1% in the feces.     

Comparative Study of Bacterial Groups within the Human Cecal and Fecal Microbiota

The composition of the human cecal microbiota is poorly known because of sampling difficulties. Samples of cecal fluid from eight subjects were collected via an intestinal tube. Feces were also collected. Total anaerobes, facultative anaerobes, bifidobacteria, and Bacteroides were enumerated by culture methods, and the predominant phylogenetic groups were quantified by molecular hybridization using a set of six rRNA-targeted probes. The numbers of strict anaerobes, bifidobacteria, Bacteroides, and members of the Clostridium coccoides group and Clostridium leptum subgroup were lower in the cecum. Facultative anaerobes represented 25% of total bacteria in the cecum versus 1% in the feces.     

Effects of age and starvation on the gastrointestinal microflora and the heat resistance of fecal bacteria in rats.

The microflora of the gastrointestinal tract in rats 1 day to 100 weeks old, of the cecal contents and wall in starved rats, and of heat-treated feces of normal rats was determined by cultural examination. Streptococci, staphylococci, lactobacilli, actinobacilli, and coliforms colonized the tract during the 1st week of life. Bacteroidaceae, veillonellae, catenabacteria (composed of eubacteria and anaerobic lactobacilli), clostridia, bifidobacteria, anaerobic gram-positive cocci, fusiform bacteria, curved rods, and spirochetes appeared when the rats were 2 to 4 weeks old. Yeasts were slower in colonizing the tract than any other organism. Dramatic changes occurred in the microflora of rats 2 to 4 weeks of age. There was a time lag between the changes in enterococcal and coliform populations. The enterococcal population was depressed over a period from 2 to 6 weeks of age. Bifidobacteria showed a larger population at 4 to 9 weeks than at any other age. The microflora of the stomach was the same as that of the small intestine, with some exceptions. It differed markedly from that of the cecum. The ratio of total aerobic count to anaerobic count gradually increased in the stomach, but decreased in the cecum, with advance in age. The microorganisms distributed in the tract could be divided roughly into 3 types. The population of each organism, except spirochetes, in the cecal wall was approximately 1/1,000 of that in the cecal contents. One of the 2 types of spirochetes was found only in the cecal wall and in a high incidence, forming a large population. In rats starved for 48 hr, coliforms, Proteus spp., anaerobic gram-positive cocci, Clostridia, and some bacteroidaceae showed an increase in population in the cecum, but lactobacilli, veillonellae, and spirochetes decreased. The major organisms cultured from the heat-treated feces were fusiform and curved bacteria, some members of Bacillus, minor anaerobic cocci, and straight rods.     

Effect on components of the intestinal microflora and plasma neuropeptide levels of feeding Lactobacillus delbrueckii, Bifidobacterium lactis, and inulin to adult and elderly rats

The aim of this study was to compare the effects of the mixture of Lactobacillus delbrueckii subsp. rhamnosus strain GG, Bifidobacterium lactis Bb12, and inulin on intestinal populations of lactobacilli, bifidobacteria, and enterobacteria in adult and elderly rats fed the same (in quality and quantity) diet. The portal plasma levels of two neuropeptides, neuropeptide Y (NPY) and peptide YY (PYY), were also evaluated to assess the physiological consequences of the synbiotic treatment for the gastrointestinal (GI) tracts of rats of different ages. Adult (n = 24) and elderly (n = 24) male rats were fed the AIN-93 M maintenance diet. After 2 weeks of adaptation, the diet of 12 rats of each age group was supplemented with 8% inulin and with strains GG and Bb12 to provide 2.2 x 10(9) CFU of each strain g(-1) of the diet. Blood and different regions of the GI tract were sampled from all rats after 21 days of the treatment. Treatment with the mixture of strain GG, strain BB12, and inulin induced significantly different changes in the numbers of lactobacilli, bifidobacteria, and enterobacteria of the stomach, small intestine, cecum, and colon microflora. Moreover, the GG, BB12, and inulin mixture increased the concentrations of NPY and PYY for adult rats. For the elderly animals, the PYY concentration was not changed, while the NPY concentration was decreased by treatment with the GG, BB12, and inulin mixture. The results of the present study indicate that the physiological status of the GI tract, and not just diet, has a major role in the regulation of important groups of the GI bacteria community, since even the outcome of the dietary modification with synbiotics depends on the ages of the animals.     

Distribution of bifidobacteria in the gastrointestinal tract of calves

Development of gastrointestinal microflora of calves with special reference to bifidobacteria was investigated; fecal bacteria were enumerated in calves aged 3 days to 7 weeks. Bacteria were detected by using selective media, bifidobacteria using modified TPY agar with an addition of mupirocin and acetic acid and by fluorescence in situ hybridization (FISH). Bifidobacteria were dominant group of fecal flora of calves after 7 d of life, constituting 10 % of total bacterial counts. The highest bacterial concentrations were observed in rumen, cecum, and colon, the lowest in abomasum and duodenum. Bifidobacteria and lactobacilli exhibited the highest survival ability during stomach passage and dominated in all parts of the digestive tract. Bifidobacteria counts determined by FISH were significantly higher than those provided by cultivation. Modified TPY agar was highly selective and suitable for bifidobacteria isolation but FISH was shown to be a more precise method for their enumeration. Our results show that gastrointestinal microflora of calves in the milk-feeding period is similar to breast-fed infants with respect to the occurrence of bifidobacteria as a dominant bacterial group. The use of Bifidobacterium strains offers a promising way for providing beneficial effectors for calves in the milk-feeding period.     

Studies on Streptococci

The population levels of bacteria in the contents and the walls of the gastrointestinal tract of gnotobiotic rats inoculated with lactic acid bacteria (streptococci, lactobacilli, and bifidobacteria) from humans and rats were determined. Lactobacilli as well as streptococci isolated from rats colonized in the digestive tracts of the gnotobiotic rats at a high population level, characteristically highest in the stomach. On the other hand, in the rats inoculated with human lactic acid bacteria, streptococci were dominant in the lower tract. The human lactobacilli or bifidobacteria did not colonize when the organisms in each genus were inoculated together with streptococci. However, when all three genera were inoculated together, lactobacilli and bifidobacteria colonized. Observations on the species of streptococci showed that the intestinal type of streptococci was found to colonize at a high population level, but the oral type was not. Strains of the same genus of lactic acid bacteria from humans and from rats showed different colonization patterns.     

Effect on Components of the Intestinal Microflora and Plasma Neuropeptide Levels of Feeding Lactobacillus delbrueckii, Bifidobacterium lactis, and Inulin to Adult and Elderly Rats

The aim of this study was to compare the effects of the mixture of Lactobacillus delbrueckii subsp. rhamnosus strain GG, Bifidobacterium lactis Bb12, and inulin on intestinal populations of lactobacilli, bifidobacteria, and enterobacteria in adult and elderly rats fed the same (in quality and quantity) diet. The portal plasma levels of two neuropeptides, neuropeptide Y (NPY) and peptide YY (PYY), were also evaluated to assess the physiological consequences of the synbiotic treatment for the gastrointestinal (GI) tracts of rats of different ages. Adult (n = 24) and elderly (n = 24) male rats were fed the AIN-93 M maintenance diet. After 2 weeks of adaptation, the diet of 12 rats of each age group was supplemented with 8% inulin and with strains GG and Bb12 to provide 2.2 × 10⁹ CFU of each strain g⁻¹ of the diet. Blood and different regions of the GI tract were sampled from all rats after 21 days of the treatment. Treatment with the mixture of strain GG, strain BB12, and inulin induced significantly different changes in the numbers of lactobacilli, bifidobacteria, and enterobacteria of the stomach, small intestine, cecum, and colon microflora. Moreover, the GG, BB12, and inulin mixture increased the concentrations of NPY and PYY for adult rats. For the elderly animals, the PYY concentration was not changed, while the NPY concentration was decreased by treatment with the GG, BB12, and inulin mixture. The results of the present study indicate that the physiological status of the GI tract, and not just diet, has a major role in the regulation of important groups of the GI bacteria community, since even the outcome of the dietary modification with synbiotics depends on the ages of the animals.     

Effects of high dietary cellulose on the large intestinal microflora and short-chain fatty acids in rats

Wistar rats fed diets containing different contents of cellulose or 5% transgalactosylated oligosaccharides (TOS) for 7 weeks were examined for faecal microflora and caecal short-chain fatty acids. High (15%) cellulose diet showed remarkable increases in concentrations of faecal bifidobacteria and caecal butyrate with a reduced concentration of propionate as compared with the other diets. TOS-fed rats showed strikingly increased concentrations of bifidobacteria and acetate. A comparison of pH values between the caecal contents and faeces suggested more fermentation of cellulose in the distal than proximal part of the large bowel of rats.     

双歧杆菌对失血后肠源性感染的预防作用

本文观察双歧杆菌对失血后肠源性感染的预防作用,将大鼠分为假处理、失血、双歧杆菌＋失血,新霉素＋失血４组。后两组实验前分别灌注双歧杆菌或新霉素,假处理动物麻醉插管不放血,后３组动物放血２ｏ％,６ｈ后每组１０只动物活杀取样。发现：失血组大鼠１０ｈ存活率降低,血浆ＥＴ、ＩＬ—１升高,细菌培养阳性标本增多,小肠杆／球菌比值增大,与假处理组相比差异显著。双歧杆菌治疗组大鼠时间存活率增加,血浆ＥＴ、ＩＬ—１无明显升高,细菌培养阳性标本减少,杆／球菌比例正常,与失血组相比差异显著。新霉素治疗组上述各项指标与失血组相比无显著改善。提示双歧杆菌能有效地预防失血后肠源性感染。     

Gastrointestinal flora of cotton rats

The gastrointestinal (GI) flora of cotton rats was examined. No lactobacilli were detected in any part of the GI tract. Anaerobes, including Peptococcaceae, Bacteroidaceae, bifidobacteria and eubacteria, were the predominant bacteria in the stomach, small intestine, caecum and faeces. Aerobes and facultative anaerobes, including Enterobacteriaceae and streptococci, were detected at low numbers and very low frequency of occurrence in all parts of the GI tract. Sixty-one isolates of bifidobacteria were recovered from the stomach, small intestine, caecum and faeces of cotton rats. They were identified as Bifidobacterium animalis, B. pseudolongum biovar a and b. The study showed that the GI flora of cotton rats seem to be very different from the GI flora in other rodents.     

Genomic diversity and relatedness of bifidobacteria isolated from a porcine cecum

This study initially involved the isolation of a number of bifidobacteria from either the lumen or the epithelium of a porcine cecum. A total of 160 isolates were selected at random on MRS plates containing cysteine hydrochloride (0.5 g/liter) and mupirocin (50 mg/liter). All were identified as bifidobacteria based on fructose-6-phosphate phosphoketolase activity. Following genomic digestion with the restriction enzyme XbaI and pulsed-field gel electrophoresis (PFGE), the isolates produced 15 distinct macro-restriction patterns. Several of the PFGE patterns differed by only 1, 2, or 3 DNA fragments and were grouped as related patterns into seven PFGE types, termed A through G. The related patterns appeared to show genomic plasticity within the isolates arising from chromosomal mutations or possibly horizontal transfer of plasmids. The relative frequency of each PFGE type was maintained within each cecal sample, with PFGE type E representing approximately 50% of the isolates. Randomly amplified polymorphic DNA PCR, cell morphology, whole-cell protein profiling, 16S ribosomal DNA sequencing, and DNA-DNA hybridization were used to determine if the seven apparently unrelated PFGE types represented genetically distinct isolates. Four groups were identified: PFGE types A, C/D/G, B/E, and F, and these appeared to represent Bifidobacterium minimum, Bifidobacterium pseudolongum subsp. pseudolongum, and Bifidobacterium pseudolongum subsp. globosum and two new species, respectively. The data demonstrate the presence of considerable genomic diversity within a relatively simple bifidobacteria population, consisting of 15 distinct strains representing four groups, which was maintained throughout the porcine cecal contents and epithelial layer.     

双歧杆菌对门静脉血内毒素影响初步研究

本实验以大鼠为动物模型,探讨在肠道微生态失调的状态下,用大量双歧杆菌(Bifidobacteria)灌服,借以拮抗外源性需氧革兰氏阴性杆菌的生长繁殖,从而使肠源性内毒素自门静脉的吸收减少。对正常鼠、脱污染鼠、再污染鼠、治疗鼠和非治疗鼠,进行不同肠段的双歧杆菌、需氧革兰氏阴性杆菌的测定和门静脉血内毒素测定。结果表明:双歧杆菌对肠道需氧革兰氏阴性杆菌的生长繁殖,具有明显的生物拮抗作用,同时伴有相应的门静脉血内毒素水平的降低。     

胆管结扎对大鼠肠道双歧杆菌组成的影响

目的分析胆管结扎对SD大鼠肠道双歧杆菌菌群结构组成的影响。方法采集手术前3 d和手术后2周5只模型组和5只对照组大鼠的粪便样品,提取粪便样品中微生物的混合DNA进行双歧杆菌类群特异性PCR-DGGE,结合主成分分析技术比较2组大鼠在手术前后肠道内双歧杆菌结构组成的变化。结果DGGE图谱及其主成分分析表明手术后对照组和模型组大鼠肠道双歧杆菌菌群的结构组成明显不同,主要表现在假长双歧杆菌的数量在模型组显著增加,而动物双歧杆菌却明显减少。结论胆管结扎导致SD大鼠肠道双歧杆菌结构发生异常变化。     

Effect of Bacterial Contamination on Cecal Size and Cecal Contents of Gnotobiotic Rodents

In the present investigation the effect of various bacterial contaminations of gnotobiotic mice and rats on cecal size is presented. Of the species tested, Bacteroides oralis and Fusobacterium nucleatum did not establish in germ-free mice. Streptococcus mutans, Clostridium difficile, a Neisseria strain and two recent cecal isolates established, but failed to exert an effect upon the cecum of mice. A group K streptococcus and B. fragilis increased the cecal size apparently by increasing the levels of water-soluble protein, peptides, and carbohydrates in the cecal contents. Mixed ileal bacteria decreased the cecal size by preventing accumulation of soluble proteins and carbohydrates in the cecum. A Peptococcus strain caused a reduction by lowering the levels of insoluble material in the cecum. When this strain was combined with two Clostridium isolates and introduced into gnotobiotic rats, 50 to 65% cecal reduction was observed. This polycontamination did not decrease the per cent water of the cecal contents but caused lower levels of both soluble and insoluble material to accumulate in the cecum. No net nitrogen absorption from the distal small intestine occurred in either the germ-free or polycontaminated rats.     

Dietary fructooligosaccharides alter the cultivable faecal population of rats but do not stimulate the growth of intestinal bifidobacteria

The effect of fructans on the cultivable faecal community of Bio Breeding rats fed diets containing 5% (m/v) food-grade fructooligosaccharide (FOS) was investigated. Culturing of faecal material using chicory inulin as the sole carbohydrate source revealed the presence of a greater diversity of inulin-utilizing bacterial species in FOS-fed rats as compared with the control rats, although both contained species which effectively utilized inulin. The majority of cultivable inulin-utilizing species fell within the Clostridium coccoides group and Clostridium leptum subgroup, some of which were related to previously cultured butyrate-producing bacteria from the intestines of various animals. The impact of FOS on the growth of the indigenous bifidobacteria community and three inulin-utilizing isolates was assessed using real-time polymerase chain reaction. While dietary FOS was found to stimulate the growth of all three inulin-utilizing isolates, no growth stimulation of the indigenous bifidobacteria community occurred over the duration of the feeding trial.     

Safety evaluation of probiotic bifidobacteria by analysis of mucin degradation activity and translocation ability

Although probiotic-containing nutrient formulas for infants and toddlers have become very popular, some adverse effects related to translocation of probiotic strains have been reported. We assessed the safety of probiotic bifidobacteria that have been used in clinical investigations and proven to have beneficial effects, by analyzing mucin degradation activity and translocation ability. Mucin degradation activities of three probiotic bifidobacteria strains; Bifidobacterium longum BB536, Bifidobacterium breve M-16V and Bifidobacterium infantis M-63, were evaluated by three in vitro tests comprising growth in liquid medium, SDS-PAGE analysis of degraded mucin residues, and degradation assay in Petri dish. All test strains and control type strains failed to grow in the liquid medium containing mucin as the only carbon source, although good growth was obtained from fecal sample. In the SDS-PAGE analyses of mucin residues and observation of mucinolytic zone in agar plate, the three test strains also showed no mucin degradation activity as the type strains, although fecal sample yielded positive results. In another study, a high dose of B. longum BB536 was administered orally to conventional mice to examine the translocation ability. No translocation into blood, liver, spleen, kidney and mesenteric lymph nodes was observed and no disturbance of epithelial cells and mucosal layer in the ileum, cecum and colon was detected, indicating that the test strain had no translocation ability and induced no damage to intestinal surface. These results resolve the concern about bacterial translocation when using bifidobacteria strains as probiotics, which have been tested in various clinical trials, supporting the continuous use of these probiotic strains without anxiety.     

Ultrastructure of the enlarged cecum in germfree rats

Summary The cecum of germfree rats, as studied by light microscopy and scanning and transmission electron microscopy, differs in many respects from the cecum of conventional rats. Epithelial cells in germfree rats are taller and have larger nuclei and longer microvilli than similar cells in conventional rats. The cecal mucosa of germfree rats shows a larger variability in the arrangement of the crypts of Lieberkühn than does the mucosa of conventional rats. Some crypts are funnel-shaped and connected close to the mucosal surface with adjacent similar crypts to form long valleys. Less wide crypts open on elevated regions of the mucosal surface. The lamina propria of germfree animals is devoid of plasma cells but rich in mast cells. Germfree animals show hypertrophy of the tunica muscularis externa.In conventional rats the cecal lumen contains a large variety of morphologically different bacteria. However, the lumen of the crypts of Lieberkühn contains only one type of elongated bacteria, which are present in large amounts. This finding suggests that symbiotic relations may be of particular importance in the crypts of Lieberkühn in the cecum.Supported by research grants from the Swedish Medical Research Council (206), Knut och Alice Wallenbergs Stiftelse and Stiftelsen Therese och Johan Anderssons Minne.