Advances in the design of probiotic products for the prevention of major diseases in dairy cattle

Probiotics are frequently used for multiple objectives and the majority of applications are performed both in human beings and in different animals. The specificity of species showed by the members of the indigenous microbiotia led us to isolate lactic acid bacteria (LAB) from their natural bovine ecosystems and to select those with probiotic potentiality. The beneficial probiotic LAB were isolated from the vaginal tract and mammary gland of adult heifers, faeces and oral cavity of newborn calves. Bacterial strains and their numbers varied in each tract under study. Their surface properties, evaluated using the MATH test, revealed that the higher number of low hydrophobic strains were isolated from vaginal tract, mammary gland or faeces. The capability of autoaggregation also differed with higher degree in those isolated from vagina, whereas those that originated in the mammary gland or faeces showed low autoaggregation characteristics. The production of antagonistic substances showed that the production of hydrogen peroxide was higher in the strains isolated from the vaginal tract, while those able to produce organic acid were isolated from all the environments. A few strains were able to produce bacteriocins and were isolated only from the mammary gland and faeces, but not from the vaginal tract. Further studies are being performed to complete the functional characterization of the strains in order to evaluate their survival in the environmental conditions of each tract. Finally, the selected strains could be combined for the design of probiotic products to be used both in adult cows and in neonates, based on the host-specificity, due to their autochthonous origin and their potential use in the tract where they were isolated.     

摄入含嗜酸乳杆菌NCFM和乳双歧杆菌Bi-07的益生菌补充剂增强免疫功能的动物实验研究

目的测定与验证摄入含特定乳酸菌株组合（嗜酸乳杆菌NCFM和乳双歧杆菌Bi-07）一定剂量的益生菌补充剂对动物（小鼠）免疫功能的影响。方法SPF昆明种小白鼠经口连续分别给予0．25、0．50、1．50g／kgBW的益生菌补充剂4周,进行迟发型变态反应试验、溶血素滴度测定、NK细胞活性测定等。结果在小白鼠迟发型变态反应试验中,中、高剂量组足跖增厚值均高于对照组,差异有显著性（P〈0．05）;对受试动物血清溶血素抗体滴度水平的影响的实验中,中、高剂量组的抗体积数高于对照组,差异均有显著性（P〈0．05）。NK细胞活性测定中,高剂量组脾NK细胞活性增强,差异有非常显著性（P〈0．01）。结论含该两种特定乳酸菌株的益生菌补充剂被小自鼠摄入一定剂量后,起到了增强小白鼠细胞免疫、体液免疫功能及NK细胞活性的作用。     

Good adhesion properties of probiotics: a potential risk for bacteremia?

The ability to adhere to human intestinal mucus was tested for lactic acid bacteria of clinical blood culture, human fecal and dairy origin. The blood culture isolates were found to adhere better than the dairy strains. Of the Lactobacillus rhamnosus strains (nine clinical, 10 fecal and three dairy), blood culture isolates adhered better than the fecal strains. Although these results indicate a trend for blood culture isolates to bind to intestinal mucus in higher numbers than strains of dairy and human fecal origin, other factors are also likely to be involved in the etiology of lactobacillemia since some of the clinical Lactobacillus isolates exhibited a relatively low level of adhesion.     

Differences in the gut bacterial flora of healthy and milk-hypersensitive adults, as measured by fluorescence in situ hybridization

We enumerated the predominant gut genera from fecal samples of nine healthy and eight milk-hypersensitive adults both before and after 4 weeks Lactobacillus rhamnosus GG (LGG) supplementation. The anaerobic intestinal microflora of milk-hypersensitive adults was found to resemble that of healthy adults. LGG-consumption resulted in a significant increase in the number of bifidobacteria in healthy but not in milk-hypersensitive subjects, as well as a general increase in bacterial numbers in all other bacterial genera tested in both groups. In conclusion, the composition of the gut microbiota in milk-hypersensitive adults appears to be normal. LGG may have potential in reinforcing the endogenous flora.     

Structural analysis of the Lactobacillus rhamnosus strain KL37C exopolysaccharide

The exopolysaccharide from the lactic acid bacterium Lactobacillus rhamnosus strain KL37C isolated from human intestinal flora was prepared by sonication of bacterial cell mass suspended in water followed by centrifugation and cold ethanol precipitation of the supernatant. The polysaccharide material was purified by gel permeation chromatography on an TSK HW-50 column and characterised using chemical and enzymatic methods. On the basis of sugar and methylation analysis and 1H, 13C, 1D and 2D NMR spectroscopy the exopolysaccharide was shown to be composed of the following pentasaccharide repeating unit:-->3)-alpha-D-Glcp-(1-->2)-beta-D-Galf-(1-->6)-alpha-D-Galp-(1-->6)-alpha-D-Glcp-(1-->3)-beta-D-Galf-(1-->     

双歧杆菌抗生素耐药性研究进展

目前,由于抗生素的广泛、大量使用,耐药菌株急剧增多,加剧了耐药菌对人类健康和生态环境的威胁。有研究表明,益生菌自身含有的耐药基因或耐药质粒等可通过基因水平转移传递给人体肠道中的致病菌,导致耐药菌感染。随着双歧杆菌相关微生态制剂的广泛应用,通常以活菌形式进入人体的双歧杆菌,与肠道内原籍菌群混合生长,致使其携带的耐药性基因片段在肠道菌群中水平转移,从而导致某些致病菌具有耐药性。因此,研究双歧杆菌等益生菌的耐药性基因转移有着十分迫切的意义。本文总结了双歧杆菌的耐药性,分析了双歧杆菌的耐药机理,为进一步筛选安全的双歧杆菌菌株提供理论依据。     

肠道菌群失调致抑郁症发病机制的研究进展

抑郁症是一种由多因素相互作用引起的复杂的精神疾病。其患病率达15%,带来的负担占全球疾病负担的12.3%,且有很高的致残、致死率,严重危及到人类的健康。抑郁症的病因并不清楚,一般认为是社会、环境、个体三方面因素相互作用的结果。肠道微生物作为人体最大、最直接的外环境,在抑郁症形成中的作用已明确,但具体机制仍不清楚。近年来,随着肠道微生态研究的兴起以及关于"抗抑郁药安全且有效"的说法被提出,肠道菌群失调在抑郁症的发生和发展中的作用越来越受到重视,"微生物-肠-脑轴"被提出,本文就肠道菌群失调致抑郁症可能的发病机制及微生态治疗作一综述。     

The use of bacterial spore formers as probiotics

The field of probiosis has emerged as a new science with applications in farming and aqaculture as alternatives to antibiotics as well as prophylactics in humans. Probiotics are being developed commercially for both human use, primarily as novel foods or dietary supplements, and in animal feeds for the prevention of gastrointestinal infections, with extensive use in the poultry and aquaculture industries. The impending ban of antibiotics in animal feed, the current concern over the spread of antibiotic resistance genes, the failure to identify new antibiotics and the inherent problems with developing new vaccines make a compelling case for developing alternative prophylactics. Among the large number of probiotic products in use today are bacterial spore formers, mostly of the genus Bacillus. Used primarily in their spore form, these products have been shown to prevent gastrointestinal disorders and the diversity of species used and their applications are astonishing. Understanding the nature of this probiotic effect is complicated, not only because of the complexities of understanding the microbial interactions that occur within the gastrointestinal tract (GIT), but also because Bacillus species are considered allochthonous microorganisms. This review summarizes the commercial applications of Bacillus probiotics. A case will be made that many Bacillus species should not be considered allochthonous microorganisms but, instead, ones that have a bimodal life cycle of growth and sporulation in the environment as well as within the GIT. Specific mechanisms for how Bacillus species can inhibit gastrointestinal infections will be covered, including immunomodulation and the synthesis of antimicrobials. Finally, the safety and licensing issues that affect the use of Bacillus species for commercial development will be summarized, together with evidence showing the growing need to evaluate the safety of individual Bacillus strains as well as species on a case by case by basis.     

Assignment of <Emphasis Type="Italic">Lemna gibba</Emphasis> L. (duckweed) bioassay for <Emphasis Type="Italic">in situ</Emphasis> ecotoxicity assessment

To narrow the differences between the results obtained from radionuclides and heavy metal ecotoxicity investigations in the laboratory and in the abandoned uranium mines, a few standardised plant bioassay procedures were selected from the literature for testing with Lemna gibba L. The bioassay procedures were tested in situ and ex situ. The laboratory culturing was performed in batch and semicontinuous modes. The results revealed that most of the standardised plant bioassay procedures require modification for the L. gibba bioassay to predict the actual effects under field conditions. L. gibba performed relatively better in the field than laboratory batch cultures despite that the batch cultures had many-fold higher nutrient concentrations than in the field. For instance, the phosphorus concentration of the mine tailing water was 0.13 ± 0.09 μg l⁻¹ in the field, while the literature range for phosphorus in the laboratory culture media is 13.6–40 mg l⁻¹. L. gibba growth in the laboratory batch culture was influenced by speciation changes due to consumption of nutrients, CO₂ and O₂ phase exchanges, and excretion of organic substances by the test plants. Semicontinuous culture modes performed significantly better than batch cultivation even after 10× dilution of the nutrient solution. The growth behaviour revealed that L. gibba exhibited intrapopulation and probiotic interaction for best performance. Growth performance of L. gibba was influenced by the anions that balanced essential cations despite equal cation concentration in the culture media; e.g., the best growth was observed in culture media that had more SO₄²⁻ than Cl⁻. Water samples from the field had higher SO₄²⁻ concentrations than Cl⁻. The test vessel material, sterilisation and axenic culturing procedures also influenced the sensitivity of the bioassay. These, for instance, and a few others are neither described nor reported in most standard Lemna tests or the literature. Thus, this work presents results of a series of tests conducted on the selected methods. Common and possible errors and corrective measures in assigning L. gibba bioassay from laboratory population levels to field community levels are discussed.     

Rapid identification of potentially probiotic Bifidobacterium species by multiplex PCR using species-specific primers based on the region extending from 16S rRNA through 23S rRNA

This study aimed at developing a novel multiplex polymerase chain reaction (PCR) primer set for identification of the potentially probiotic Bifidobacterium species B. adolescentis, B. animalis subsp. animalis (B. animalis), B. bifidum, B. breve, B. longum biovar infantis (B. infantis), B. animalis subsp. lactis B. lactis, B. longum biovar longum (B. longum) and B. pseudolongum. The primer set comprised specific and conserved primers and was derived from the integrated sequences of 16S and 23S rRNA genes and the rRNA intergenic spacer region (ISR) of each species. It could detect and identify type strains and isolates from pharmaceuticals or dairy products corresponding to the eight Bifidobacterium species with high specificity. It was also useful for screening of the related strains from natural sources such as the gastro-intestinal tract and feces. We suggest that the assay system from this study is an efficient tool for simple, rapid and reliable identification of Bifidobacterium species for which probiotic strains are known.