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1.
Summary The ligated gut test (LGT) is the standard method for the examination ofEscherichia coli strains for enterotoxin production in pigs. As solid pig feed has been associated with diarrhea, soya products (the main protein source for piglets) were investigated with the same test asE. coli strains.After injection of different soya products into ligated segments of the small intestine fluid accumulation was observed, indicating a net excess of secretion. The factor in soya products responsible for this effect was found to be thermostable, as its effect was unaltered after heating at 120°C during an hour. No indications of a possible allergic phenomenon accounting for the fluid accumulation were found.From the results of this study it is concluded that soyabean products can produce results in the LGT similar to those produced by enterotoxigenicE. coli strains.  相似文献   

2.
Four adsorbant drug preparations, Kaopectate, colloidal Attapulgite, noncolloidal Attapulgite and Pepto-bismol were investigated for their effects on fluid accumulation in ligated segments of pig intestine inoculated with enteropathogenic Escherichia coli. Two anti-inflammatory drugs. aspirin and methylprednisolone, and two antibiotics, lincomycin and polymyxin B, were also tested. All the drugs except the two anti-inflammatory products were given by injection into the lumen of the intestine. Aspirin was given orally and methylprednisolone was given intramuscularly. The antibiotics were tested at levels at which they had no significant antibacterial effect in in vitro tests. The adsorbant drugs colloidal Attapulgite and Pepto-bismol were shown to be effective in reducing fluid accumulation in ligated segments of pig intestine infected with enteropathogenic E. coli. In the case of Peptobismol this effect was associated with an antibacterial effect as well as an antitoxic effect, probably due to its adsorbant properties. It is possible that an aspirin-like effect in the gut due to the active ingredient bismuth subsalicylate may have contributed to the effectiveness of Pepto-bismol. Colloidal Attapulgite was demonstrated to have an antitoxic effect but did not have an antibacterial effect.

In high doses, the anti-inflammatory drugs acetylsalicylic acid and methylprednisolone were marginally effective in reduction of fluid accumulation in the same test system. Lincomycin was shown to reduce intestinal fluid secretion, whereas polymyxin B had no effect.

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3.
Two experiments, using the ligated intestinal segment technique, were conducted to determine whether the pituitary hormone prolactin (PRL) could reduce Escherichia coli-induced fluid loss into the small intestine of 2- to 3-week-old pigs. Inoculation of 10(6) to 10(8) enteropathogenic E coli organisms into ligated jejunal segments caused a significant accumulation of luminal fluid within 12 hours. In the first experiment, intraluminal inoculation with 0.5 mg of ovine PRL along with the bacteria did not have any effect on fluid accumulation. Systemic IV treatment of the animals with 1.0 mg of ovine PRL at 3-hour intervals, beginning either immediately after or 9 to 10 hours before intestinal ligation, did not significantly (P less than 0.05) reduce fluid accumulation as compared with control animals. In the second experiment, IM administration of 100 microgram of thyrotropin-releasing hormone (TRH) at 3-hour intervals, beginning 6 hours before intestinal ligation, significantly (P less than 0.05) increased circulating PRL concentrations, as measured by radioimmunoassay. However, TRH treatment did not reduce the accumulation of luminal fluid in E coli-inoculated segments.  相似文献   

4.
Milk from sows whose progeny developed post weaning E. coli diarrhoea (PWD milk) and from sows which were immunized by intramuscular vaccination using a homologous strain of E. coli (immune milk) were tested in ligated segments of pig intestine. The results showed that PWD milk neutralized the enterotoxigenic, fluid accumulating capacity of the lysate of the disease-causing E. coli pathogen. A similar effect was seen by using immune milk (Table I). Neither PWD milk nor immune milk contained sufficient antibacterial activity to neutralize the fluid accumulating capacity of live cultures of E. coli O149:K91, while such activity was contained in immune serum. It is concluded that milk from sows whose progeny developed PWD contains antibodies capable of neutralizing the enterotoxigenic effects of the homologous E. coli organisms. It is suggested that the presence in milk from these sows of antibody-mediated activity against enteropathogenic E. coli organisms may be instrumental in preventing the disease in the progeny during the suckling period and consequently, when this protective milk supply stops at weaning, the disease may develop in susceptible animals, mainly because their own production of specific E. coli antibodies is insufficient to prevent PWD.  相似文献   

5.
A study was conducted to determine whether intestinal fluid collected from various portions of bovine intestine differed in its effect on production of K99 pili by Escherichia coli. The small and large intestines of 7 calves, euthanatized 4 hours after a final feeding of milk, were divided into 6 to 9 segments from which intraluminal fluids were collected. Depending on the amount of fluid collected, up to 20 E coli strains that express K99 pili were grown on media prepared from the content of each specimen and then were tested for K99 pilus expression. In general, intestinal fluid from the most proximal small intestinal segments were more suppressive to K99 pilus expression than was fluid from more distal segments of small intestine. Only about 20% of the E coli test strains expressed K99 pili when grown on medium prepared from proximal small intestinal segmental fluid, whereas greater than 90% did when grown on medium prepared from distal small intestinal segmental fluid. Fluid from the large intestine varied considerably from calf to calf in its effect on K99 pilus expression. A correlation was found between K99 pilus expression and pH of the intestinal fluid, with the lower pH values (characteristic of proximal intestinal segmental fluid) being suppressive. The correlation between K99 pilus production and the pH of the medium was verified, using defined laboratory media adjusted to various pH values. Strains of E coli grown in medium at or below pH 5.5 failed to express K99 pili, whereas the same strains when grown in medium at or above pH 6.5 expressed K99 pili in abundance.  相似文献   

6.
E. coli serogroups 02, 08, 083, 0103 and 0120 were isolated from seven camels with diarrhoea of which 02, 08, and 083 were found to be enterotoxigenic on rabbit ligated ileal loop test. Out of 125 apparently healthy camels, 75 strains of E. coli were isolated. The majority of isolates were susceptible to gentamycin, nitrofurantoin, trimethoprim plus sulphonamide, neomycin, kanamycin and chloramphenicol.  相似文献   

7.
A study was undertaken to determine the prevalence of enterotoxigenicity among Escherichia coli isolated from calves with diarrhea and from a control group of normal calves. The test organisms consisted of 200 E. coli recovered from scouring calves less than two weeks of age and 100 E. coli from normal calves. The enterotoxigenicity of the cultures was evaluated by three methods, namely, injection of ligated segments of piglet intestine, injection of ligated segments of calf intestine and oral inoculation of suckling mice. Live cutures of all the test organisms were used for the ligated intestine studies whereas sterile broth culture supernatants were used in the suckling mouse tests. Of the isolates from scouring calves, 36% were enterotoxigenic in the piglet intestine and 28% in the calf intestine. Amongst the isolates from normal calves, none was enterotoxigenic in the piglet intestine and one was enterotoxigenic in the calf test system. The ligated piglet intestine was considered unsuitable for determining the enterotoxigenicity of bovine E. coli, whereas the ligated calf intestine test was satisfactory and correlated completely with the suckling mouse test. The enterotoxigenic E. coli of bovine origin produced an enterotoxin that resembled the heat stable enterotoxin of typical porcine enteropathogenic E. coli.  相似文献   

8.
为研究大肠杆菌多重耐药调控基因rob与不同动物源性及多重耐药水平之间的关系，选取临床分离的不同动物源性大肠杆菌5株及大肠杆菌药敏质控株ATCC25922，在对其进行主要治疗药物耐药性检测的基础上，分别以其染色体DNA为模板，通过PCR反应扩增出大肠杆菌多重耐药调控基因rob，将该基因分别与克隆载体pMD18-T连接，连接产物转化至大肠杆菌JM109感受态细胞中，对经酶切与PCR反应鉴定为阳性的克隆质粒进行了核苷酸序列测定。测序结果表明：不同动物源性大肠杆菌的rob基因与Gen-Bank中该基因的核苷酸序列及所推导的氨基酸序列的同源性较高。不同源性大肠杆菌的rob基因的核苷酸序列与其动物源性有关，该基因的核苷酸序列的个别突变位点可能影响AcrAB外输泵的表达水平，进而影响其多重耐药水平。  相似文献   

9.
为了探讨中药与抗菌药物联用对大肠杆菌耐药性的作用效果，本研究对河南部分地区采集的样品（50份）进行分离鉴定、生化试验及致病性试验，对分离鉴定后的致病性猪大肠杆菌选用12种中药采用K-B法进行耐药性检测，将筛选出来的中药与抗生素进行中西联用对致病性大肠杆菌做体外抑菌试验，并分析中西药联用对大肠杆菌的抑制作用。结果显示，采集的50份样品有23株菌符合大肠杆菌的分离培养特性和生化特性，且23株菌均为致病性大肠杆菌；通过耐药性检测，23株试验菌株对测试的中药均有不同程度的耐药性，其中试验菌株对甘草耐药率最高（82.6%），其次为生地（78.2%），而对黄柏（17.3%）和白头翁（21.7%）耐药性较低，具有一定的敏感性；体外抑菌试验结果发现，中药与抗生素联用均有不同程度的抑菌效果，其中黄柏、白头翁与抗菌药物联用的抑菌效果最明显。以上结果说明中药与抗菌药物联用不仅可以抑制大肠杆菌的耐药性，还可以延缓大肠杆菌耐药性的产生。  相似文献   

10.
Nineteen antisera produced in pigs against 14 enteropathogenic and five nonenterotoxigenic porcine strains of Escherichia coli were tested for their ability to inhibit gut loop fluid accumulation induced by homologous and heterologous organisms. In addition, four antisera produced in pigs by an intensive series of intravenous inoculations and three by a less intensive series of intramuscular injections of a polyvalent E. coli vaccine were evaluated. Antisera were also produced in rabbits against eight strains of porcine enteropathogens and tested in pig gut loops. Fluid inhibiting activity was detected in prevaccinal sera of pigs but not of rabbits. This activity was significantly increased following immunization. When single strains of E. coli were used for immunization the activity of the antisera against heterologous organisms varied considerably from one test strain to another and was usually much less than that against the homologous organism. The activity against heterologous organisms could not be associated with relatedness of the O, K and H antigens of the vaccine and the test strains. Antisera produced against a vaccine made by combining three strains were shown to exert inhibitory effects on heterologous organisms similar to those against homologous organisms. Considerably less activity against homologous and heterologous organisms was present in antisera produced by the series of intramuscular compared with the series of intravenous injections.  相似文献   

11.
Three-hundred and fifty-eight E. coli strains isolated from piglets were tested for the presence of hemagglutinins by the use of the active hemagglutination test with or without mannose. Additionally 86 strains from the mentioned number of strains were investigated for the presence of common fimbriae using the same method but growing the strains in media especially suited for the development of this kind of fimbriae. These 358 strains and additionally 202 E. coli strains were tested using antisera for 987P and K88 antigens. It was found, using the active hemagglutination test, that 51.4% of the strains were hemagglutinating. The hemagglutinating strains carried the K88 antigen. All these strains were isolated from new-born and weaned piglets with enterotoxic form of colibacillosis, called also E. coli diarrhea. From cases of this form of colibacillosis originated also 26.7% of the strains in which common fimbriae (type 1) were detected. This result was obtained when the BHI medium was used for cultivation. In case of TSA medium only 2.3% of strains were positive. No specific or common fimbriae were found in strains recovered from septic form of colibacillosis and oedema disease (called also enterotoxaemic form of colibacillosis). No strain of 560 examined showed the presence of fimbrial 987P antigen.  相似文献   

12.
The protective effects of high levels of O115 antibodies and K88 antibodies in the sera of hyperimmunized rabbits on the intestinal loop dilation elicited by live cultures of Escherichia coli O115: K88:H39 and its enterotoxins were examined. K88 antibodies did not prevent fluid accumulation when live E coli O115:K88:H39 or its enterotoxins were injected into ligated loops in rabbits actively immunised with K12:K88 or when K88 antiserum was mixed directly with the challenge shortly before injection into the loops. In two of six rabbits immunised with heat-killed O115 E coli the live strain failed to elicit a fluid response and in two others the response was reduced. In all cases the O115 antiserum inhibited the fluid response evoked by the live, homologous bacteria, but not by enterotoxin preparations, when the serum was mixed directly with the challenge before injection.  相似文献   

13.
多重PCR快速检测奶牛乳房炎3种主要病原体   总被引：10，自引：0，他引：10  
奶牛乳房炎是引起奶牛业经济损失的一种重要疫病,目前还没有快速、特异检测奶牛乳房炎主要致病原的方法。本试验根据金黄色葡萄球菌、无乳链球菌、大肠杆菌各自保守的16S或23S rRNA基因序列,合成了3对特异性引物,建立了三重PCR检测方法。特异性试验表明,该方法对所有参与测试的金黄色葡萄球菌、无乳链球菌和大肠杆菌都能扩增出各自的阳性条带,而对所有参与测试的对照菌株则不能扩增出任何条带。敏感性试验表明该方法能检测到4个菌的金黄色葡萄球菌、无乳链球菌和2个菌的大肠杆菌。对送检的乳房炎奶样36份直接进行PCR检测,金黄色葡萄球菌阳性7份,无乳链球菌阳性2份,大肠杆菌阳性6份。  相似文献   

14.
OBJECTIVE: To determine the antibacterial activity of bovine lactoferrin hydrolysate (bLf-lysate) alone or in combination with other antimicrobials against antimicrobial-resistant Escherichia coli strains isolated from baby pigs. SAMPLE POPULATION: 3 clinical strains of E coli were isolated from baby pigs with severe diarrhea and designated as strains 9061, 9062, and 9065. PROCEDURE: The broth microdilution checkerboard and fractional inhibitory (or bactericidal) concentration index were used to evaluate the antibacterial effect elicited by bLf-lysate in combination with kanamycin, gentamicin, cephalothin, cefamandole, penicillin G, ampicillin, tetracycline, erythromycin, or rifampicin against the 3 strains of E coli. RESULTS: The 3 strains of E coli were susceptible to gentamicin and rifampicin but highly resistant to most of the other antimicrobials tested, except for strain 9061 that was also susceptible to cephalothin but intermediately inhibited by kanamycin and cefamandole. Synergistic growth-inhibitory activity was observed between bLf-lysate and gentamicin against 1 strain of E coli (strain 9062); synergistic bactericidal activity was found between bLf-lysate and rifampicin against all 3 strains of E coli. Moreover, partial synergy was observed between bLf-lysate and kanamycin, gentamicin, cephalothin, or cefamandole against the strains of E coli, but this partial synergistic activity was mostly seen against only 1 of the strains. Little interaction between bLf-lysate and tetracycline, ampicillin, penicillin G, or erythromycin was observed against the clinical strains of E coli. CONCLUSIONS AND CLINICAL RELEVANCE: A combination of bLf-lysate and certain antimicrobials may prove clinically effective against antimicrobial-resistant strains of E coli.  相似文献   

15.
Twenty-four haemolytic Escherichia coli strains were isolated from dogs with diarrhea. The strains were serotyped and analysed by polymerase chain reaction (PCR) for genes encoding virulence factors associated with E. coli that cause diarrhea in animals. Adhesion antigen production was deduced from haemagglutination experiments. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) of heat extracts was also used as an indication for the production of adhesive structures. The majority of the strains was shown to produce this type of virulence factor. Adhesion and invasion tests of the strains and Caco-2 cells showed that all strains adhered and that two were invasive. The two invasive strains were positive in the intimin PCR and one of them also contained genes encoding CS31A. The PCR for heat stable toxin (ST) was positive in only four strains, as was the presence of F17 fimbrial genes. Surprisingly, 19 strains had intact P fimbrial operons, coding for an adhesin involved in urinary tract infection (UTI). The cytotoxic necrotising factor 1 (CNF1) gene, also mainly found in UTI was likewise detected in these 19 strains. Cytolethal distending toxin (Cdt) genes were found in five strains. The high number of strains positive for CNF1 and P fimbriae prompted us to test the strains in a multiplex PCR used to test E. coli isolated from UTI in various species for 30 virulence associated genes. The data showed that the majority of the diarrhea isolates have virulence factor profiles highly similar to UTI E. coli isolates from dogs. This raises the question whether these isolates are real intestinal pathogens or "innocent bystanders". However, since CNF1 producing necrotoxic E. coli (NTEC) strains isolated from humans, pigs and calves with diarrhea appear to be highly related to our strains, it might be that in dogs this type of isolate is capable of causing not only UTI, but also diarrhea. If this is the case and this type of isolate is "bifunctional", domestic animals likely constitute a reservoir of NTEC strains which can be also pathogenic for humans.  相似文献   

16.
165 (93.7%) of 175 E. coli strains isolated from various materials of different animal species were correctly identified as E. coli with help of commercially available Bactident E. coli (E. Merck, D-6100 Darmstadt). Further 52 strains of the family of Enterobacteriaceae (2x Providencia sp., 2x Salmonella sp., 7 Citrobacter sp., 9 Proteus sp., 15 Klebsiella sp., 17 Enterobacter sp.) were correctly not identified as E. coli by this test. Bactident E. coli is a suitable test for rapid identification of E. coli in veterinary bacteriology.  相似文献   

17.
为调查新疆部分地区E.coli O157：H7的感染情况和菌株致病性,从新疆阿克苏、伊犁、塔城3个地区的牛场采集新鲜粪样564份,对E.coli O157：H7进行分离与鉴定。利用E.coli营养肉汤（EC肉汤）对样品进行增菌后,用山梨醇麦康凯培养基（SMAC）平板选择性培养,再经过4-甲基伞形酮-β-D葡萄糖醛酸苷培养基（MUG）的筛选,对疑似菌株进行生化和PCR鉴定,并将分离鉴定到的菌株进行小鼠攻毒试验。结果显示,从伊犁地区采集的样品中共分离出2株E.coli O157：H7（Y166和Y226）,其检出率为0.88%;小鼠攻毒试验中,Y166和Y226试验组小鼠在48 h内全部死亡,具有一定致病性;从阿克苏、塔城所采样品中未分离到E.coli O157：H7。  相似文献   

18.
At present, no standard protocol has been described to detect the presence of Escherichia coli O157 in cattle faeces. Therefore, the sensitivity of 26 different isolation methods was determined in order to recommend a method of choice. Faeces samples from 17 different beef cattle at a farm previously found positive for E. coli O157 were subdivided into a total of 40 samples. It was not known whether the 17 cattle shed E. coli O157 at the time of sampling. At another farm where cattle have been found negative for E. coli O157 on different occasions, five faeces samples were collected. Two methods yielded the highest sensitivity (74%): 6h enrichment in modified tryptone soya broth supplemented with novobiocin (mTSBn) followed by an immunomagnetic separation (IMS) with (i) Dynal beads or (ii) Captivate beads and selective plating on Rainbow agar (RA) plates. Enrichment for 6h was significantly better than 24h enrichment. Only after 24h, buffered peptone water (BPw) was significantly better than mTSBn. A sensitivity of 82% was obtained only when the two most sensitive tests were done simultaneously. Because none of the tests gave 100% sensitivity, it can be concluded that isolation rates of E. coli O157 from bovine faeces using only one of the tested procedures results in an underestimation of the incidence of E. coli O157 in cattle. Performing more than one test on the samples must be considered.  相似文献   

19.
The study was carried out to investigate the incidence of Escherichia coli O157 in raw materials, foodstuffs and the agricultural environment. Of a total of 987 samples examined, 22 strains (2.2%) were identified as E. coli O157 and 10 of them as E. coli O157:H7. Cefixime-Tellurite MacConkey sorbitol agar (CT-SMAC) agar and Biosynth culture medium (BCM) E. coli O157:7 medium were used for the isolation. The virulence factors (stx1, stx2, eae, and ehxA genes) were identified by polymerase chain reaction (PCR). Most strains were isolated from the mechanically deboned poultry meat (nine), minced meat (six) and raw milk (four). One strain was isolated from beef carcass and two strains from waste water. No strains were were found in mass for sausages, refreshment salads, swabs of pork and poultry carcasses and faeces of cattle and pigs. Ten strains from the 22 identified proved to be positive for all factors of virulence. They were isolated from minced meat (four), raw milk (four), waste water (one) and swab from beef carcass (one). Sensitivity to the antimicrobial drugs ampicillin (AMS), ampicillin-sublactam (SAM), tetracycline (TET), ofloxacine (OFL), cefuroxime (CRX), chloramphenicol (CPM), gentamicine (GEN), colistin (COL), cephalozine (CLZ), cefoxitin (CXT), aztreonam (AZT), and sulphamethoxazole + trimethoprim (COT) was tested using the standard dilution technique and disc diffusion test. Minimum inhibitory concentrations (MIC) characteristics (MIC(50), MIC(90), MIC range) and inhibitory zone diameter were determined for each strain. As determined by MICs, the resistance to tested antibiotics in E. coli O157 isolates was found to AMS (90.9%), CLZ (81.8%), CRX (63.6%), CXT (72.7%), CPM (72.7%), TET (81.8%), SAM (59.1%), COT (9.1%), COL (63.61%), AZT (9%) and GEN (4.5%). The similar results were obtained using the disc diffusion method. The differences were found relating to SAM, CXT, CMO and TET. Resistance against one or more antibiotics was found in 95.4% of E. coli O157. Only one strain was susceptible to all tested antibiotics. Most of the strains were resistant to ampicillin and cephalozine. Eight different resistance phenotypes were demonstrated in E. coli O157.  相似文献   

20.
A cross-sectional study was conducted to determine the prevalence and characteristics of verocytotoxigenic Escherichia coli (VTEC) on 25 dairy farms each located in Waller field and Carlsen field farming areas in Trinidad. On each selected farm, faecal samples were collected from milking cows, calves and humans; rectal swabs were obtained from pet farm dogs; bulk milk was sampled as well as effluent from the milking parlour. Escherichia coli was isolated from all sources on selective media using standard methods. Isolates of E. coli were subjected to slide agglutination test using E. coli O157 antiserum, vero cell cytotoxicity assay to detect verocytotoxin (VT) and heat labile toxin (LT) production, the polymerase chain reaction (PCR) to detect VT genes, and the dry spot test to screen for E. coli O157 and non-O157 strains. In addition, faecal samples from animal and human sources were tested for VT genes using PCR. Of a total of 933 E. coli isolates tested by the slide test, eight (0.9%) were positive for the O157 strain. The vero cell cytotoxicity assay detected VT-producing strains of E. coli in 16.6%, 14.6%, 3.2% and 7.1% of isolates from cows, calves, farm dogs and humans respectively (P < 0.05; chi(2)). For LT production, the highest frequency was detected amongst isolates of E. coli from calves (10.8%) and the lowest (0.0%) amongst isolates from humans and bulk milk (P < 0.05; chi(2)). Of the 61 VT-producing isolates by vero cell cytotoxicity assay tested by PCR, the VT, LT and eae genes were detected in 62.3%, 4.9% and 1.6% respectively (P < 0.05; chi(2)). Amongst the 45 E. coli isolates that were VT positive (vero cell) or VT-gene positive by PCR, 2.2%, 2.2%, 4.4% and 6.7% belonged to non-O157 strains O91, O111, O103 and O157, respectively, as determined by the Dry spot test. Detection of VTEC strains in milk and dairy animals poses a health risk to consumers of milk originating from these farms. In addition, the demonstration of VTEC strains in humans, VT gene in faecal samples and E. coli isolates as well as non-O157 VTEC strains of E. coli are being documented for the first time in the country.  相似文献   

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