植物乳酸菌对致病性大肠杆菌的抑制试验

本试验进行了植物乳酸菌、乳酸、醋酸及MRS对致病性大肠杆菌的体外抑制试验。结果表明：分离自植物的乳酸菌培养物上清液对致病性大肠杆菌K88、987P、F41均有较强的抑制作用,与其它对照组比较差异极明显;并且证明了结果与植物乳酸菌产酸无关,可能与其产生抑菌素相关,这为研究与开发抗仔猪大肠杆菌病的微生态制剂奠定了基础。     

乳酸菌与大肠杆菌相互作用的研究

本文研究了保加利亚乳杆菌L5和嗜热链球菌G7共培养物对大肠杆菌的抑制作用和大肠杆菌对乳酸菌的影响.结果表明,乳酸菌对大肠杆菌的抑制作用强弱受其活力和大肠杆菌浓度的影响.乳酸菌活力高抑制作用强,大肠杆菌浓度低抑制作用强.同样,大肠杆菌可以影响乳酸菌的产酸、产香、生长、产粘、水解蛋白等能力.     

乳酸菌对肠道微生物屏障的调控作用

乳酸菌是机体重要的生理性细菌,对肠道健康起着重要作用。首先它是肠道优势菌群,在肠道内起着决定性作用;其次乳酸菌具有较强的定植抵抗力,黏附于肠道黏附上皮;同时代谢产物也有较强的抑菌作用。在这一系列作用机制的调控下,使得乳酸菌能够有效地抵制有害菌的入侵,维持肠道健康。     

乳酸菌对仔犬生长性能、发病率、粪中大肠杆菌数量的影响

试验选用60只健康的德国牧羊犬仔犬,共计10窝,随机将每窝仔犬分成2组,试验组20-30日龄饲喂混有3.2 g乳酸菌素的奶粉,30日龄断乳后继续饲喂混有3.2 g乳酸菌的饲料,与对照组进行比较。以此来研究日粮中添加乳酸菌对仔犬生长性能、发病率、肠道菌群的影响。结果表明:在日粮中添加乳酸菌可提高断乳仔犬生长性能,增重明显,饲料利用率提高;降低仔犬发病率、死亡率(P<0.05)及缩短腹泻时间;降低粪便pH值约0.3-0.5单位,使断乳前厌氧菌群呈优势分布,同时增加乳酸菌的含量、减少大肠杆菌的含量(P<0.05)。     

2株乳酸菌对鸡源致病性大肠杆菌的体外抑制试验

对2株乳酸菌对鸡源致病性大肠杆菌的体外抑制进行了研究,结果表明,3种处理方法均能不同程度地抑制大肠杆菌的生长,但以先接种乳酸菌后接种大肠杆菌的效果较好。该结果为分离的2株乳酸菌在动物生产中的应用奠定了理论基础。     

VFA和黏蛋白对肠道微生物和肠道疾病的影响

日粮组成和消化道健康直接影响动物的健康．胃肠道是病原菌侵入机体的直接人口。一旦消化器官的保护性机制出了问题，胃肠道内正常菌群以外的病原微生物便会定植．随后侵入到宿主体细胞和组织。保护胃肠道不受病原微生物侵害的因素有：IgA的分泌、胃肠道菌群的平衡、保护性生理内环境的维系、黏蛋白保护层、消化道蠕动。现就VFA及黏蛋白对肠道微生物和肠道疾病的影响作一介绍。     

番鸭肠道乳酸菌的分离鉴定及抑菌性能

通过革兰染色、菌落形态观察、生化分析鉴定、牛津杯抑菌试验、Caco-2细胞黏附试验对分离到的6株乳酸产生菌进行研究。结果显示:经16SrDNA序列测定,比对分析6株乳酸产生菌与鼠李糖乳杆菌、乳酸乳球菌乳亚种、唾液乳杆菌、乳链球菌、哥伦比亚肠球菌和鼠乳杆菌高度同源。6株乳酸菌抑菌试验检测显示:对大肠杆菌、沙门菌、蜡样芽胞杆菌和金黄色葡萄球菌具有很强的抑菌效应,以CM3菌株的抑菌效果最强。同时,这6株乳酸菌对Caco-2细胞均有一定的黏附能力。结果表明:6株番鸭肠道乳酸产生菌能够黏附于肠道模型Caco-2细胞上并具有较强的抑菌活性,但其黏附性能及保护机制还有待进一步研究。     

猪源乳酸菌对致病性大肠杆菌的抑制试验

大肠杆菌病是仔猪常见的消化道疾病,也是导致仔猪死亡的主要原因之一.据资料报道,仔猪大肠杆菌病引起的仔猪死亡约占仔猪死亡的90%以上,对该病的防治,主要包括疫苗的免疫、抗生素和化学药物治疗几个方面.其中疫苗免疫,因肠道微生物种类与抗原决定簇复杂性,免疫效果常不理想;抗生素与化学药物的大量应用,易产生耐药菌株,导致仔猪肠道菌群失调;抗生素与化药的排出和残留,造成环境污染并危害人、畜健康.乳酸菌作为动物肠道的优势菌群之一,其对生物体的有益作用已被许多研究结果所证实[1].实验室或临床实践研究表明,乳酸菌对肠道细菌如大肠杆菌、沙门菌等引起的疾病有治疗和保健作用.乳酸菌通过生长繁殖产生乳酸、乙酸等有机酸和抑菌素等,降低肠道的pH值,改善内部微环境,抑制有害菌的生长,其代谢产物对动物体本身还具有较强的营养作用.因而乳酸菌成为微生态制剂的主要原料之一.因此,为了开发以乳酸菌为主的针对防治仔猪肠道疾病尤其是大肠杆菌病的微生态制剂,进行了试验,现将试验结果报道如下.     

新型乳酸菌微生态制剂对大肠杆菌感染仔猪生长性能与肠道菌群和血清生化的影响

笔者挑选28头体重12 kg左右的健康仔猪,按体重分成4组,每组7头单舍饲喂,以探讨新型乳酸菌微生态制剂对大肠杆菌感染仔猪的生长性能、肠道菌数及血液生化影响。试验结果可以看出,新型乳酸菌微生态制剂可明显提高仔猪的日增重(P<0.05),在仔猪采食量没有显著增加的情况下平均日增重呈上升趋势,同时降低腹泻发病率。测定饲喂新型乳酸菌微生态制剂的仔猪在大肠杆菌K88感染(攻毒)后7 d的血清生化指标,除血浆低密度脂蛋白胆固醇含量极显著地升高外,其他如葡萄糖、尿素氮、谷草转氨酶、高密度脂蛋白胆固醇等均没有变化;乳酸菌和攻毒并存相互作用,大大降低了血浆谷丙转氨酶的活性(P<0.05);新型乳酸菌微生态制剂可使仔猪小肠部分的微生物区系得到改善,显著增加其乳酸菌的数量(P<0.1),而对其他菌群如厌氧菌、耗氧菌和大肠杆菌等没有影响。     

乳酸菌对动物肠黏膜黏附的相关因子及黏附机理

乳酸菌作为一种典型的益生菌，是肠道内的优势菌群，在改善肠道微生态环境、抑制肠道病原菌生长等方面具有重要作用。乳酸菌在宿主肠道中持久发挥生理功能的前提是能在宿主上皮细胞膜上发生黏附。因此，黏附性是乳酸菌发挥作用的功能性指标，也是当前研究的热点。本文就乳酸菌黏附的相关物质和黏附机理等方面进行综述。     

乳酸杆菌对病原菌粘附肉鸡肠粘液的影响

研究嗜酸乳杆菌、禽大肠杆菌O78、大肠杆菌ATCC 25922、鸡白痢沙门氏菌和鼠伤寒沙门氏菌与肉鸡不同肠段粘液糖蛋白的粘附性能,探讨嗜酸乳杆菌对四种病原菌的粘附排斥作用.结果表明,在不同的肠道部位,嗜酸乳杆菌、鸡白痢沙门氏菌和鼠伤寒沙门氏菌与肠粘液糖蛋白的粘附能力不同,而禽大肠杆菌O78、大肠杆菌ATCC 25922在各肠段粘液上的粘附性能相近;在相同的肠道部位,所试菌与肠粘液糖蛋白的粘附能力有差异,其中嗜酸乳杆菌的粘附作用最强;嗜酸乳杆菌对所试病原菌均有不同程度的粘附排斥作用,其中对鸡白痢沙门氏菌的粘附排斥较强,而对大肠杆菌ATCC25922的则较弱.     

卵黄抗体对ETEC粘附仔猪小肠上皮细胞的体外抑制作用研究

采用热抽提法提取 4种肠毒素性大肠杆菌菌毛蛋白 :K88、K99、F41和 987p。分别制成单价或多价的菌毛蛋白白油佐剂抗原 ,对产蛋鸡进行胸部肌肉分点注射免疫 ,初免后 2周加强免疫 1次。收集高效价卵黄抗体。用所获得各卵黄抗体对体外分离的初生仔猪小肠上皮细胞进行体外粘附抑制试验。结果表明 ,各种菌毛卵黄抗体均能特异地显著抑制相应大肠杆菌对仔猪上皮细胞的粘附 ,而对其他血清型大肠杆菌对肠上皮细胞的粘附无抑制作用     

In vitro inhibition of ETEC K88 adhesion by pea hulls and of LT enterotoxin binding by faba bean hulls

Enterotoxigenic Escherichia coli (ETEC) expressing K88 (F4) adhesins are associated with post‐weaning diarrhoea in piglets. Different grain fractions from pea (Pisum sativum) and faba bean (Vicia faba) were tested in vitro for their capacity to counteract aetiological factors, which contribute to the development of diarrhoea. In detail, adhesion of E. coli O149:K91:K88ac (ETEC K88ac) to grain legume products, intended to impair the colonization of the host, was studied as well as interference with receptor binding of the pathogen’s heat‐labile enterotoxin LT, intended to reduce toxin‐inflicted gut cell damage. When comparing different pea and faba bean products tested for their binding capacity of ETEC K88ac, especially pea hulls, but also whole pea meal, starch‐enriched and protein‐enriched pea meal, and digestion‐resistant pea hull and meal fractions showed a higher binding of ETEC K88ac than faba bean products. In contrast to the ETEC K88ac adhesion results, bean hulls proved more effective than pea hulls in preventing GM1 receptor binding of LT. Previous small intestinal segment perfusion experiments we performed with ETEC K88ac‐challenged piglets indicated that both pea and bean hulls have the potential for successful application in diarrhoea prophylaxis and treatment, which is in agreement with and refined by our detection of their different modes of functioning.     

Absence of host specificity for in vitro adhesion of probiotic lactic acid bacteria to intestinal mucus

Adhesion of probiotic lactic acid bacteria (LAB) has been reported to be host species specific. Host specificity is regarded as a desirable property for probiotic bacteria and therefore recommended as one of the selection criteria. However, previous studies have indicated that LAB originating from one host adhere well also to the mucus of other species. The aim of the study was to investigate the host specificity of LAB adhesion in human, canine, possum, bird and fish mucus in vitro. An in vitro mucus adhesion model was utilized in this study using immobilized mucus from faeces or intestinal material of these hosts. The results indicate that the adhesion trait was not host specific but rather was characteristic to LAB species. In conclusion, mucus adhesion properties are more dependent on the LAB strain than on the host. This suggests that animal models in probiotic adhesion assays may be more applicable to other species than thought earlier. Positive health effects facilitated by adherent probiotics in humans may also denote the possibility of similar outcome in other species and vice versa.     

Isolation and identification of AIDA-I receptors in porcine intestinal mucus

Porcine AIDA-I positive Escherichia coli causes diarrhea in neonatal piglets and AIDA-I adhesin is an important virulence factor involved in intestinal colonization with biofilm formation. This biofilm consists of AIDA-I(+)E. coli bacteria stratified within mucus layers covering the intestinal mucosa. Based on the intimate interaction between AIDA-I(+)E. coli and mucus within the intestinal biofilm, we hypothesized that porcine intestinal mucus contains receptor(s) for AIDA-I adhesin. Since porcine AIDA-I receptors have not been identified, we employed affinity chromatography and in vitro adhesion assays to investigate AIDA-I binding proteins in porcine intestinal mucus that might serve as receptors for attachment of AIDA-I positive E. coli. We demonstrated that porcine mucus contains 65 and 120kDa proteins (p65 and p120) that bind with high affinity to purified AIDA-I adhesin and that AIDA-I positive E. coli binds to these proteins with higher affinity than do AIDA-I negative mutant. The identity of p65 was not determined based on LC-MS/MS data, whereas p120 was matched to two nuclear proteins (namely, DNA damage binding protein and splicing factor 3b) and one cytoplasmic protein, which is an IgG Fc binding protein. Based on similar amino acid homology, molecular weight, structural similarity to mucin and reported evidence of being secreted by goblet cells into the intestinal lumen, we think that the IgG Fc binding protein is most likely candidate to serve as a potential receptor in intestinal mucus for AIDA-I adhesin.     

Drug resistance in strains of Escherichia coli isolated from the intestinal tract of pigs in Norway.

Faecal samples from 95 healthy pigs and samples of jejunal content from 85 piglets suffering from colienterotoxaemia were tested for the presence of drug resistant E. coli strains. Practically all pigs in both groups harboured E. coli strains resistant to one or more of the 6 antibiotics/chemotherapeutic agents tested (Oxytetracycline, streptomycin, sulphaisodimidin, neomycin, ampicillin, chloramphenicol). Almost 100% of healthy and approx. 90% of diseased pigs harboured strains resistant to Oxytetracycline, streptomycin and sulphaisodimidin. Pigs with strains resistant to neomycin, ampicillin and chloramphenicol were less frequently found. The predominant coliform flora consisted of E. coli strains” resistant to Oxytetracycline, streptomycin and sulphaisodimidin in 71% to 81% of diseased pigs and in 47% to 69% of the healthy pigs. In diseased pigs ¾ of the animals had a coliform flora dominated by neomycinresistant E. coli strains.Of the 721 resistant E. coli strains isolated from healthy pigs, 11% were single resistant while the corresponding figure for the 518 resistant strains isolated from diseased pigs was 6%. Thus 89% and 94% of strains showed simultaneous resistance to 2 or more antibiotics. E. coli strains resistant to 3 or more drugs were found in approx. 60% and 70% of the isolates from healthy and diseased animals, respectively. Oxytetracycline/streptomycin/sulphaisodimidin resistance was most commonly found, approx. 22% and 38% of the strains from healthy and diseased pigs, respectively, showing this resistance pattern.Transmission of drug resistance which was examined in E. coli strains originating from the diseased pigs was demonstrated in approx. 76% of the isolates. The incidence of drug resistance transfer in single, double, triple and quadruple resistant strains was 11%, 68%, 97% and 98%, respectively.     

Inhibition of adhesion of F18+ Escherichia coli to piglet intestinal villous enterocytes by monoclonal antibody against blood group H-2 antigen

Enterotoxigenic and verotoxigenic F18⁺ Escherichia coli colonising the pig small intestine, adhere to receptors on intestinal villous enterocytes by F18 fimbriae. The aim of the present study was to define the F18R nature. The knowledge on the nature of this receptor could be important for the development of receptor-based treatments against F18⁺ E. coli-induced disease. The adhesion of F18⁺ E. coli to pig intestinal villous enterocytes was analysed in an in vitro assay. The adhesion of F18⁺ E. coli but not of F4ac⁺ E. coli was strongly inhibited by monoclonal antibodies (mAb) with blood group H-2 specificity. Conversely, blood group H-1 specific mAb could not inhibit the adhesion of F18⁺ E. coli nor F4ac⁺ E. coli. Moreover, the blood group H-2 trisaccharide strongly inhibited the adhesion of F18⁺ E. coli, but only partially the adhesion of F4ac⁺ E. coli. These data demonstrate that the F18 receptor contains the blood group antigen H-2 (-fuc-(1-2)-β-Gal-(1-4)-GlcNAc) as major carbohydrate.     

健康畜禽肠道大肠杆菌耐药性及整合子-基因盒检测

采用微量肉汤稀释法检测455株大肠杆菌对24种抗菌药物的敏感性;多重PCR检测菌株Ⅰ、Ⅱ、Ⅲ型整合酶基因;采用PCR-RFLP和PCR-测序法对整合子-基因盒进行序列分析。结果显示,455株菌除对头孢唑啉、头孢曲松、头抱噻呋和阿米卡星耐药率低于40％外,对其余药物表现出高耐药率,99．23％菌株呈多重耐药性;455株菌Ⅰ型整合子阳性率87．69％,Ⅱ型整合子1．98％,未检出Ⅲ型整合子;随机选取的204株整合子阳性菌中174株（85．29％）扩增出了基因盒可变区。基因盒主要以编码氨基糖苷腺苷基转移酶和二氢叶酸还原酶的aadA、dfrA基因为主,耐药基因排列成Ⅰ型整合子8种基因盒,Ⅱ型整合子3种基因盒。Ⅰ型整合子以dfrA1-aadA1（32．76％）基因盒为主,其次是aadA22（24．14％）和dfrA17-aadA5（24．14％）。Ⅱ型整合子以d厂rA1-sat2-aadA1（66．67％）为主,Ⅱ型整合子阳性菌含有I型整合子-基因盒;菌株含整合子-基因盒越复杂,其多重耐药性越严重。结果表明,本次分离的健康动物肠道大肠杆菌耐药非常严重,整合子-基因盒分布广泛,已成为耐药基因储库,对耐药基因扩散起重要作用。     

我国健康猪源大肠杆菌对四环素类药物耐药性的Meta分析

旨在系统评价我国健康猪源大肠杆菌对四环素类药物耐药性的情况,为养殖业合理用药决策提供依据.计算机搜索PubMed、Web“sci-ence、SinoMed、CNKI等10个数据库.应用Revman 5.3软件进行Meta分析,并对各研究间异质性进行评价.共纳入20篇符合条件的研究,共4 343株分离自健康猪源的大肠杆菌...