脆弱拟杆菌在炎症性肠病、结直肠癌促进、调控及防治中的作用

近年来人们越来越重视肠道菌群在肠源性疾病的发生、发展及防治中所发挥的作用。脆弱拟杆菌(Bacteroides fragilis,BF)是定殖于人体肠道中的共生菌,对肠道健康有多种影响,是健康人群及腹泻、腹膜炎、腹内脓肿、败血症、炎症性肠病等临床病例最常见的肠道微生物。随着人们对脆弱拟杆菌的深入研究,发现脆弱拟杆菌与炎症性肠病(inflammatory bowel disease,IBD)、结直肠癌(colorectal cancer,CRC)有密切关系。通过对脆弱拟杆菌与IBD、CRC之间的关系进行综述,探究脆弱拟杆菌在IBD、CRC促进、调控及防治中的作用,为IBD、CRC的早期干预和治疗提供新思路,为开发基于脆弱拟杆菌的药物提供数据与思路。     

拟杆菌的研究及应用

拟杆菌大量存在于宿主体内,对宿主的健康起着重要的作用。当宿主微生态平衡被破坏时它又是条件致病菌,使宿主患病。主要总结了最近10年来国内外学者对拟杆菌的研究状况,重点对拟杆菌的致病及益生机理进行了阐述。此外,还介绍了几株有重要应用价值的拟杆菌,并就以后的研究趋势作了展望。     

母乳性黄疸患儿肠道菌群宏基因组学研究

目的探讨母乳性黄疸(BMJ)患儿的肠道菌群情况。方法采用鸟枪法宏基因组测序方法,对16例BMJ患儿及16例正常婴儿的肠道菌群进行研究。结果 BMJ组与对照组中样品菌种丰度及菌群种类总的水平上差异无统计学意义(P0.05);在部分菌种上有差异,双歧杆菌、脆弱拟杆菌及多形拟杆菌在BMJ组中较对照组少(P0.05);在菌群基因的功能通路上差异也有统计学意义(P≤0.05),尤其是在糖合成和代谢基因功能通路中,BMJ组比对照组表达较少些,差异有统计学意义(P0.05)。结论 BMJ患儿肠道菌群的种类、丰度与正常同龄婴儿总体上差异不大,在菌种上有部分差异,双歧杆菌、脆弱拟杆菌及多形拟杆菌在BMJ患儿肠道中含量较少,可补充双歧杆菌、拟杆菌制剂使BMJ患儿的肠道菌群平衡。同时,在基因功能通路表达上,BMJ患儿与正常同龄婴儿有显著差别,特别是糖合成和代谢通路,可深入研究。     

脆弱拟杆菌β-内酰胺酶的纯化及免疫学特性

利用层析结合PAGE回收蛋白的方法对临床分离的脆弱拟杆菌(Bacteroides tragilis)55的β-内酰胺酶进行纯化,纯酶与Liposome-CPS-K混合制备抗血清,并建立了lgG—ELISA和western blotting方法。其测定结果表明,脆弱拟杆菌的β-内酰胺酶不同于其它拟杆菌和肠道杆菌染色体编码的β-内酰胺酶(p<0.001),具有种的特异性。     

罗伊乳杆菌LE16益生特性的研究

目的研究罗伊乳杆菌LE16的益生特性。方法通过体外和动物实验,评价罗伊乳杆菌LE16的益生特性。结果该菌株对p H 2.5的强酸和0.3%高胆盐环境均有良好的耐受性。对引起肠道感染的几种病原菌均有不同程度的拮抗,尤其对枯草芽胞杆菌、伤寒沙门菌、单核细胞增生李斯特菌及蜡样芽胞杆菌的抑制作用最强。对肠道菌群正常和失调的小鼠均具有调节功能。结论罗伊乳杆菌LE16具有良好的益生性能,可作为益生菌菌株开发应用于食品和保健食品中。     

脆弱拟杆菌BF839治疗寻常型银屑病：一项单臂、开放初步临床试验

银屑病被认为是一种T细胞主导的炎症性疾病,其发病与肠道菌群失调密切相关。脆弱拟杆菌 (Bacteroides fragilis,BF) 可通过调节T细胞的细胞因子表达起抗炎作用。目前尚无脆弱拟杆菌用于治疗银屑病的相关报道,文中率先探究脆弱拟杆菌BF839对银屑病的治疗效果。选择2019年4月至2019年10月广州医科大学附属第二医院就诊的27例银屑病患者,维持原治疗不变,口服脆弱拟杆菌BF839 12周,对比治疗前后银屑病皮损面积与严重程度指数 (Psoriasis area and severity index,PASI) 评分,统计治疗12周后药物减停率。结果表明,12周试验完成率为96.3% (26/27),12周PASI30 (PASIN定义为治疗后PASI评分下降≥N%的患者比例) 为65.4%,PASI50为42.3%,PASI75为19.2%;治疗前PASI评分为9.1±5.9,治疗12周后PASI评分为5.8±4.9,具有显著统计学差异 (P<0.01);治疗12周后皮肤瘙痒程度用视觉模拟量表 (Visual analog scale,VAS) 评分有效率为42.3%,治疗前VAS评分为2.9±2.2,治疗12周后VAS评分为2.3±2.1,无显著统计学差异 (P>0.05)。患者治疗12周内不良反应率为3.8% (1/26),其中便秘1例,药物减停率为60.0%。以上结果提示脆弱拟杆菌BF839可能对银屑病治疗有一定疗效,可降低PASI评分及药物使用率,不良反应少,值得进一步研究。     

益生芽孢杆菌对动物免疫功能影响研究进展

益生芽孢杆菌是一种新型的微生态制剂,其抗性好,具有调节动物肠道微生态平衡、促进机体消化与吸收、增强动物免疫功能、提高动物生产性能等益生效应,在动物养殖业中得到了广泛的应用。本文主要综述了益生芽孢杆菌对动物免疫器官、特异性免疫、非特异性免疫和红细胞免疫等免疫功能的影响,免疫调节和产生抗菌物质两方面的作用机理,以及影响免疫效果的因素,提出有待研究的方向和解决的方法,为益生芽孢杆菌的应用提供理论参考。     

腹内感染的细菌学研究

本文对外科腹内感染150例进行了需氧与厌氧的细菌学研究。结果表明腹内感染的病原菌都是消化道内的正常菌群,需氧菌以大肠杆菌等革兰氏阴性杆菌为主,而厌氧菌则以吉氏拟杆菌等脆弱群拟杆菌多见。感染多为几种细菌的混合感染,尤其是需氧菌与厌氧菌的混合感染。并对内源性细菌引起感染的致病机理进行了讨论。     

益生元及其作用概述

益生元及其作用概述重庆医科大学检验系微生物教研室重庆６３００４６蒋虹胡宏人肠道细菌大致分为两大类,一类是对人类有益的,如双歧杆菌、乳杆菌等;一类是对人无益或有害的,如一些肠杆菌和梭菌等。增加体内双歧杆菌的数量与活性的方法有两种,应用益生菌和益生元。１...     

草鱼树突状细胞的分离鉴定及益生芽孢杆菌对其免疫功能的影响

为揭示草鱼(Ctenopharyngodon idellus)树突状细胞(Dendritic cells)的生物学特性及益生芽孢杆菌对其免疫功能的影响, 研究通过草鱼体外细胞培养技术分离获得草鱼DCs, 对其形态学特征、生物学功能及膜表面标记分子的表达进行了分析鉴定; RT-PCR检测了益生芽孢杆菌对草鱼DCs免疫相关细胞因子表达的影响。结果表明草鱼DCs具有典型的树突状形态, 可有效地激活T淋巴细胞的增殖并具有迁移能力。LPS刺激可促进其成熟过程, 显著提升膜表面标记分子CD80/86、CD83的表达。这表明草鱼DCs和哺乳动物DCs在形态和功能上具有高度相似性。RT-PCR结果显示, 在体外条件下使用紫外照射灭活的益生枯草芽孢杆菌对草鱼DCs进行刺激后, 抗炎性因子IL-4, IL-10的表达水平显著提升(P<0.05), 并在12h时达到峰值。这表明枯草芽孢杆菌可通过促进树突状细胞分泌抗炎性因子来影响其免疫功能。以上结果为进一步研究鱼类树突状细胞的生物学特性及益生芽孢杆菌对其免疫功能的影响提供了重要的依据。     

Isolation and identification of strains of Bacteroides fragilis group from the digestive tract of Callithrix penicillata marmosets

Thirty-five strains of the Bacteroides fragilis group were isolated from oral and intestinal samples from 5 wild caught, captive Callithrix penicillata. Nine oral strains of Bacteroides fragilis (7) and Bacteroides distasonis (2), and 26 intestinal strains of Bacteroides fragilis (14) and Bacteroides distasonis (12) were identified.     

Application of quantitative real-time PCR for rapid identification of Bacteroides fragilis group and related organisms in human wound samples

Our goal was to establish a quantitative real-time PCR (QRT-PCR) method to detect Bacteroides fragilis group and related organisms from clinical specimens. Compared to conventional anaerobic culture, QRT-PCR can provide accurate and more rapid detection and identification of B.?fragilis group and similar species. B.?fragilis group and related organisms are the most frequently isolated anaerobic pathogens from clinical samples. However, culture and phenotypic identification is quite time-consuming. We designed specific primers and probes based on the 16S rRNA gene sequences of Bacteroides caccae, Bacteroides eggerthii, B.?fragilis, Bacteroides ovatus, Bacteroides stercoris, Bacteroides thetaiotaomicron, Bacteroides uniformis, Bacteroides vulgatus, Odoribacter splanchnicus (Bacteroides splanchnicus), Parabacteroides distasonis (Bacteroides distasonis) and Parabacteroides merdae (Bacteroides merdae), and detected these species by means of QRT-PCR in 400 human surgical wound infection samples or closed abscesses. The target bacteria were detected from 31 samples (8%) by culture, but from 132 samples (33%) by QRT-PCR (p-value?相似文献   

Effect of the oral intake of yogurt containing Bifidobacterium longum BB536 on the cell numbers of enterotoxigenic Bacteroides fragilis in microbiota

Enterotoxigenic Bacteroides fragilis (ETBF) strains have been suggested to be associated with acute and persistent diarrheal disease, inflammatory bowel disease and colorectal cancer, although further epidemiological studies are needed for clarification. Here, a pilot study was performed to examine the effect of the oral administration of yogurt supplemented with a probiotic strain on the cell numbers of fecal ETBF in a healthy population. Among 420 healthy adults, 38 subjects were found to be ETBF carriers, giving a prevalence of approximately 9%. Among them, 32 subjects were enrolled in an open, randomized, parallel-group study to ingest yogurt supplemented with a probiotic strain, Bifidobacterium longum BB536 (BB536Y group), for 8 weeks, with milk provided to the control group (milk group). The cell numbers of ETBF and the dominant species of the B. fragilis group were measured by a quantitative PCR method. Compared with the baseline values, there was a significant decrease in the cell number of ETBF at week 8 in the BB536Y group but not in the milk group. Linear mixed models analysis for longitudinal data revealed a significant difference in the changes of ETBF cell number between the two groups during the intervention phase. These results imply the potential of probiotic yogurt for eliminating ETBF in the microbiota, but its clinical significance needs to be evaluated in the future. This is the first report of a possible effect of probiotic intake on ETBF in the microbiota.     

Recovery of Bacteroides fragilis group from clinical specimens following antimicrobial therapy.

Over a period of 14 years (1973-1987), 3165 specimens submitted to the microbiology laboratory demonstrated the recovery of anaerobic bacteria. A total of 988 Bacteroides fragilis group isolates were recovered (0.3 isolates per specimen). Bacteroides fragilis accounted for 62% of the total of all B. fragilis group isolates, Bacteroides thetaiotaomicron for 15%, Bacteroides vulgatus for 8%, Bacteroides ovatus for 7%, Bacteroides distasonis for 6%, and Bacteroides uniformis for 2%. Of the 988 B. fragilis group isolates, 310 (31%) were recovered after the administration of antimicrobial therapy, and 129 (13%) were the single isolate recovered from the infected site at that time. The recovery rate of all members of B. fragilis group after the administration of antimicrobial therapy, when isolated alone or when mixed with other bacteria, was similar. The data illustrate the equal ability of all members of the B. fragilis group to persist in and to contribute to the inflammatory process; and provide further support for their pathogenic role.     

Construction of shuttle cloning vectors for Bacteroides fragilis and use in assaying foreign tetracycline resistance gene expression

Shuttle vectors capable of replication in both Escherichia coli and Bacteroides fragilis have been developed. Conjugal transfer of these plasmids from E. coli to B. fragilis is facilitated by inclusion of the origin of transfer of the IncP plasmid RK2. The vectors pDK1 and pDK2 provide unique sites for cloning selectable markers in Bacteroides. pOA10 is a cosmid vector containing the replication region of pCP1 necessary for maintenance in Bacteroides. pDK3, pDK4.1, and pDK4.2 contain the Bacteroides clindamycin resistance gene allowing selection and maintenance in B. fragilis of plasmids containing inserted DNA fragments. pDK3 was used to test the expression in B. fragilis of five foreign tetracycline resistance (TcR) genes. The tetA, -B, and -C markers from facultative gram-negative bacteria, as well as a TcR determinant from Clostridium perfringens, did not express TcR in B. fragilis. The tetM gene, originally described in streptococci, encoded a small but reproducible increase of TcR in Bacteroides. These studies demonstrate the utility of shuttle vectors for introducing cloned genes into Bacteroides and underscore the differences in gene expression in these anaerobes.     

Heterologous expression of the Bacteroides ruminicola xylanase gene in Bacteroides fragilis and Bacteroides uniformis

A cloned xylanase gene from the ruminal bacterium Bacteroides ruminicola 23 was transferred by conjugation into the colonic species Bacteroides fragilis and Bacteroides uniformis by using the Escherichia coli-Bacteroides shuttle vector pVAL-1. The cloned gene was expressed in both species, and xylanase specific activity in crude extracts was found to be at least 1400-fold greater than that found in the B. ruminicola strain. Analysis of crude extract proteins from the recombinant B. fragilis by SDS-PAGE demonstrated a new 60,000 molecular weight protein. The xylanase activity expressed in both E. coli and B. fragilis was capable of degrading xylan to xylooligosaccharides in vitro. This is the first demonstration that colonic Bacteroides species can express a gene from a ruminal Bacteroides species.     

Distinctive outer membrane protein and lipopolysaccharide composition of Bacteroides fragilis strains that produce metallo-beta-lactamase

The outer membrane protein and lipopolysaccharide compositions of Bacteroides fragilis strains which produced metallo-beta-lactamase were shown to be different from those of fully sensitive random clinical isolates of Bacteroides fragilis in which metallo-beta-lactamase production was not detected. This may reflect differences in the permeability barrier and provides phenotypic evidence that Bacteroides fragilis which produce metallo-beta-lactamase may belong to a separate biotype. Outer membrane profiles may provide a rapid means of identifying these problem strains.     

Heterologous gene expression in Bacteroides fragilis.

Bacteroides fragilis and other gastrointestinal tract Bacteroides are unusual gram-negative eubacteria in that genes from other gram-negative eubacteria are not expressed when introduced into these organisms. To analyze gene expression in Bacteroides, expression vector and promoter probe (detection) vector systems were developed. The essential feature of the expression vector was the incorporation of a Bacteroides insertion sequence element, IS4351, which possesses promoter activity directed outward from its ends. Genes inserted into the multiple cloning site downstream from an IS4351 DNA fragment were readily expressed in B. fragilis. The chloramphenicol acetyltransferase (cat) structural gene from Tn9 was tested and conferred chloramphenicol resistance on B. fragilis. Both chloramphenicol resistance and CAT activity were shown to be dependent on the IS4351 promoters. Similar results were obtained with the Escherichia coli beta-glucuronidase gene (uidA) but activity was just 30% of the levels seen with cat. Two tetracycline resistance determinants, tetM from Streptococcus agalactiae and tetC from E. coli, also were examined. tetC did not result in detectable tetracycline resistance but the gram-positive tetM gene conferred high-level resistance to tetracycline and minocycline in Bacteroides hosts. Based on the cat results, promoter probe vectors containing the promoterless cat gene were constructed. These vectors were used to clone random B. fragilis promoters from partial genomic libraries and the recombinants displayed a range of CAT activities and chloramphenicol MICs in B. fragilis hosts. In addition, known E. coli promoters (Ptet, Ptac, Ptrc, Psyn, and P1P2rrnB) were tested for activity in B. fragilis. No chloramphenicol resistance or CAT activity was observed in B. fragilis with these promoters.     

Detection of conjugal transfer systems in oral, black-pigmented Bacteroides spp.

Oral, black-pigmented Bacteroides spp. are important pathogens in oral anaerobic infections and dental disease. We detected conjugation systems in isolates of Bacteroides denticola and Bacteroides intermedius that transferred tetracycline resistance (Tetr) and penicillin resistance to Bacteroides buccae and to Bacteroides fragilis, an intestinal Bacteroides species. A cloned Tetr gene from B. fragilis hybridized to the transferable Tetr locus in the oral strains, indicating that genetic exchange occurs between these two groups of anaerobes.     

Bacteroides and appendicitis (author's transl)]

Bacteroides fragilis is frequently recovered from cases of appendicitis with perforation and from infections developing secondary to appendicitis. In order to assess the part played by B. fragilis in the aetiology of appendicitis, quantitative aerobic and anaerobic culture studies of the contents of 49 inflammated appendices were performed. Anaerobic gram-negative non-sporing rods were cultivated from 43 appendices in the range 10(3)-10(9)/g. A total of 1,473 isolates was differentiated by biochemical methods, and 1,374 cultures were found to belong to the saccharolytic species of the genus Bacteroides (B. fragilis, B. thetaiotaomicron, B. vulgatus, B. distasonis etc.). B fragilis was detected in 31 appendices; the species predominated in 18 samples. B theraiotamicron, recovered from 27 samples, was prevalent in 4 appendices. In one sample, B. fragilis and B. thetaiotaomicron outnumbered the other appendicular bacterial. B. vulgatus was cultivated from 12 appendices, but did once constitute the prevalent group. It has been previously shown that B. vulgatus (43% of intestinal isolates) and B. thetaiomicron predominate in the normal narge bowel flora. On the other hand, approximately 80% of pyrogenic Bacteroides strains belong to B. fragilis, B. thetaiotaomicron accounting for 19% and B. vulgatus being virtually absent. From these striking differences in species distribution the conclusion was drawn that B. fragilis possesses the highest virulence for man. Species distribution within the 1,374 appendicular isolates of saccharolytic Bacteroides (percentages of 62, 19 and 4.3 for B. fragilis, B. thetaiotaomicron, and B. vulgatus, respectively) was very similar to that encountered in clinical specimens. From the results obtained it becomes evident that pyrogenic Bacteroides, in particular B. fragilis, plays an important role in nearly 50% of cases of appendicitis.