首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 31 毫秒
1.
Fourteen strains of Yersinia species isolated from apparently healthy pigs and cattle in Nigeria were screened for four virulence markers using six test systems. These were two in vitro assays, namely, calcium dependency and autoagglutination, both at 37 degrees C, the Serény test in guinea-pigs and the detection of heat-stable enterotoxin (ST) by the rabbit ileal loop test, the ligated intestine test in pigs and the infant mouse system. Seven of the 14 strains of Yersinia were positive for one or more of these tests. Six of nine strains of Y. enterocolitica and one of four Y. intermedia were positive in one or more tests. The only strain of Y. frederiksenii isolated was negative in all six test systems. All three strains of Y. enterocolitica, serotype 0:8 and the only serotype 0:3 isolated were positive in one or more tests. However, only two of five strains of Y. enterocolitica serotype 0:12, 26, the most frequently encountered, were positive. A good correlation was observed between test results of calcium dependency, autoagglutination and Serény assays. The results indicate that cattle and pigs have the potential to transmit virulent strains of Y. enterocolitica to human beings in Nigeria.  相似文献   

2.
A total of 184 Escherichia coli isolates recovered from cows with acute mastitis were examined for recognized pathogenic mechanisms and virulence factors commonly found in pathogenic groups of E coli. A modification of the Eng procedure (for detecting complement deficiencies in serum) was used to test for resistance to different animal sera. The Sereny test (for invasiveness), infant mouse test (for heat-stable enterotoxin), and Y-1 adrenal tumor cell assay (for heat-labile enterotoxin) were used. Hemagglutination tests, using rabbit, sheep, and guinea pig RBC, were done with and without added mannose. All of the 184 isolates were serum resistant in all tested sera. None of the isolates was invasive. Only 1 isolate was positive for heat-stable enterotoxin and 2 cultures were positive for heat-labile enterotoxin. Multiple patterns of hemagglutination were observed. The majority of the isolates exhibited both mannose-sensitive and mannose-resistant hemagglutinins with guinea pig and rabbit RBC. A few strains were positive only in mannose-sensitive or mannose-resistant hemagglutination tests. A few strains were negative in all hemagglutination tests. Based on our results, E. coli from cows with acute mastitis lack the virulence factors commonly observed in other E coli groups associated with disease. Serum resistance was the only characteristic that could be related to virulence.  相似文献   

3.
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   

4.
A comparison was made between segments of pig and rabbit small intestine in their response to heat-labile (LT) and heat-stable (ST) preparations from porcine enteropathogenic Escherichia coli. Either whole cell lysates or dialysed broth culture supernatants were used as sources of LT and soft agar culture fluids as a source of ST. Whole cell lysates of all thirteen LT-producing E. coli strains tested regularly elicited fluid accumulation in rabbit gut loops. Whole cell lysates of certain E. coli strains considered to be nonenteropathogenic in pigs could also elicit a positive response in rabbit gut loops. When graded doses of LT were tested in pig and rabbit gut loops, the rabbit was more sensitive and is therefore considered preferable to the pig for quantitation of LT. In the rabbit, upper (jejunal) and lower (ileal) small intestine were compared for their response to LT and it was found that ileal loops were twice as sensitive but more prone to false positive reactions. When soft agar culture fluids of several enteropathogenic E. coli strains were tested in the rabbit, the response was inconsistent, and it was concluded that the rabbit is unsuitable for the assay of the heat-stable enterotoxin.  相似文献   

5.
The ligated gut test (LGT) is the standard method for the examination of Escherichia 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 as E. 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 degrees 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 enterotoxigenic E. coli strains.  相似文献   

6.
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   

7.
The significance of enterotoxin production and proliferative ability of Escherichia coli in the intestinal tract as related to porcine enteric colibacillosis was studied in 68 gnotobiotic pigs.

The animals were monocontaminated at seven to ten days of age with eight selected strains of E. coli. The strains were two naturally occurring porcine enteropathogens — P155 (0149:K91;K88a,c:H10) and P307 (08:K87;K88a,b:H19), two nonenteropathogenic strains — P104 (0139:K82:H1) and F11 (018-ab:K?:H14), and four enterotoxigenic derivatives of the above strains — P104(P155), P104(P307), F11(P155) and F11(P307). The response of the animals was evaluated on the basis of clinical observations and necropsy lesions 22 hours after exposure to the organisms. E.coli counts were determined at seven different levels of the intestinal tract. Cell free extracts of the intestinal contents were examined for enterotoxic activity by the ligated pig intestine loop test.

All of the strains possessing the enterotoxin plasmid produced enterotoxin in the pig's intestine and were capable of causing diarrhea. The nonenteropathogenic E. coli failed to do so. The strains possessing the P155 enterotoxin plasmid were more virulent than the corresponding derivatives with the P307 enterotoxin plasmid. Strains P155, P307 and P104(P155) proliferated in the upper small intestine at a greater rate and were more virulent than the other strains. The numbers attained in the upper small intestine by the other enterotoxigenic derivatives were comparable to those of their nonenteropathogenic parent strains.

It was considered that enterotoxin produced by E. coli was the essential factor for causing a diarrheic response in gnotobiotic pigs. The virulence of each of the tested strains appeared to be governed by the degree of enterotoxicity associated with a particular enterotoxin plasmid, the numbers attained by these organisms in the upper small intestine, (but not in the lower small intestine or in the colon), and by other undetermined factors.

  相似文献   

8.
A study was undertaken to evaluate the response of different test systems to preparations of heat-stable enterotoxin (ST) derived from Eschericihia coli strains recovered from diarrheal disease of humans, pigs and calves. Sterile broth culture supernatants of enterotoxigenic strains of E. coli were heated at 65°C for 30 minutes and tested for the presence of heat-stable enterotoxin. Three test systems, namely, ligated intestine of weaned pigs, ligated intestine of rabbits and the infant mouse test were used in attempts to detect ST in the culture supernatants. Two patterns of reaction were observed in response to ST-containing preparations: either the preparation elicited a response in the three tests or the preparation elicited a reaction only in the ligated pig intestine. A response in all three tests were observed for 5/5 human ST-producing E. coli, 5/5 bovine enterotoxigenic E. coli, 5/5 “atypical” porcine enterotoxigenic E. coli, 3/3 St+LT- porcine E. coli of serogroup O138:K81 and 4/24 LT+ST+ porcine E. coli. A response only in the ligated pig intestine was obtained with 5/5 ST+LT- porcine E. coli belonging to serogroups other than O138:K81 and to 20/24 ST+LT+ E. coli from pigs. The results are consistent with the view that there are two kinds of ST, one of which (ST1) reacts in all three tests and the other (ST2) which reacts only in the ligated pig intestine. The findings underscore the limitations of the infant mouse test as a means of detecting ST in porcine isolates of E. coli, since the test fails to detect ST produced by a large number of these E. coli strains. There appeared to be a relationship between kind(s) of ST produced and the animal species from which the producing organism was recovered.  相似文献   

9.
When pigs are weaned at two days of age large numbers of Excherichia coli appear in the anterior gut and the incidence of diarrhoea rises. The two phenomena do not appear to be directly related because the strains of E coli isolated are not serotypes previously found to be associated with neonatal pig scouring. Representative strains of the non-enteropathogenic serotypes did not produce enterotoxin and did not adhere to small intestine brush borders. Moreover when antibiotics were fed to eliminate E coli from the gut, the pigs still scoured. Rotavirus was detected in the gut contents and gut epithelium of scouring pigs and a bacteria-free filtrate of gut contents produced diarrhoea when administered to germ-free pigs. It is suggested that rotavirus may be one of the causes of the scouring seen shortly after weaning pigs at two days of age.  相似文献   

10.
It was found that oral immunisation of pigs with heat stable Escherichia coli antigens resulted in a decrease in the sensitivity of the porcine intestine to both the heat stable (ST) and the heat labile (LT) and the heat labile (LT) form of the enterotoxin produced by enterotoxigenic strains. Antitoxic factors capable of neutralising LT, but not ST, could be passively transferred in the intestinal secretions of the immunised animals.  相似文献   

11.
Altogether, 71 strains of Yersinia enterocolitica and Yersinia enterocolitica-like bacteria from porcine tonsils and pork products were examined for their ability to produce enterotoxin using the infant mouse assay. Of these, 37 strains (52.1 %) produced enterotoxin at 22 °C, 3 were positive at 4 and 22 °C, and 1 was enterotoxigenic at 22 and 37°C. No strain was positive at all 3 temperatures. The highest prevalence of enterotoxin production at 22°C was detected in serotype 0:11 (80.0%), followed by 0:3/ biotype 4 (74.2 %), and 0:12 (66.7 %). Enterotoxin production at 4°C was recorded in 2 (15.4 %) of the Yersinia kristensenii strains (0:11, 0:12) and 1 of the Yersinia enterocolitica strains, (0:3) examined. One Yersinia kristensenii strain (0:11) was enterotoxigenic at 37 °C. The results indicate that enterotoxin production is a common feature of yersiniae isolated from porcine tonsils and pork products in Norway and may represent a possible source of food borne intoxication.  相似文献   

12.
The permeability of weanling swine small intestine was estimated using measurements of filtration coefficients and equivalent pore size. Hypertonic solutions of mannitol, erythritol and urea were used to calculate reflection coefficients in the duodenum, mid jejunum and distal jejunum. Estimated effective pore radius was 6.4-7.4, 5.6-7.2 and 4.7-4.9A degrees in the three respective regions. Similarly the filtration coefficient induced by hypertonic solutions of mannitol decreased significantly in the distal jejunal segments. The results show an aboral gradient of decreasing permeability along the small intestine of the weanling pig. In situ incubation of loops in the proximal jejunum with a heat stable Escherichia coli enterotoxin for one hour did not significantly change the effective pore size as calculated from reflection coefficients of hypertonic solutions of erythritol and urea. However, the filtration coefficients of loops exposed to the enterotoxin were significantly greater than control loops with hypertonic solutions of erythritol and urea but not mannitol. This suggests the occurrence of a slight reduction in epithelial porosity. The results support the hypothesis that intestinal secretion induced by heat stable E. coli enterotoxin is not the result of an increased mucosal permeability.  相似文献   

13.
In an assay procedure, purified Clostridium perfringens enterotoxin induced the accumulation of fluid in the ileal loop of the axenic pig. The smallest amount of enterotoxin causing a positive response was 25 micrograms (1:32 titer by counterimmunoelectrophoresis [CIEP] ), and 100 micrograms (1:128 CIEP titer) caused a marked response. Possibly, diarrhea in pigs with 1:32 CIEP titer or more of enterotoxin in the feces may be associated with enterotoxigenic C perfringens.  相似文献   

14.
The effect of cholera toxin, heat labile and heat stable Escherichia coli enterotoxin on mucosal cyclic AMP concentrations was determined on the proximal jejunum of weanling pigs and young rabbits. Ligated loops were injected with solutions containing no enterotoxin for control and either cholera toxin, heat labile or heat stable E. coli enterotoxin. The loops were drained after either two, four or six hours incubation at which time accumulated fluid was recorded and mucosal samples removed for determination of cyclic AMP concentration. In the rabbit, cholera toxin and heat labile, but not heat stable E. coli enterotoxin stimulated intestinal secretion while in the pig all three enterotoxins induced net fluid accumulation. Cholera toxin and heat labile, but not heat stable E. coli enterotoxin elevated rabbit mucosal cyclic AMP concentrations. In the pig these enterotoxins had no significant effect on mucosal cyclic AMP concentrations. The results are inconsistent with the hypothesis that the adenyl cyclase system is an essential step for enterotoxin induced intestinal secretion. The activation of intestinal adenyl cyclase by bacterial enterotoxins may only be an associated and not a necessary event for the stimulation of intestinal secretion.  相似文献   

15.
1125 and 1146 E. coli strains isolated from suckling and weaned piglets with diarrhea, respectively, and 724 strains from healthy piglets were tested for the presence of fibriae and production of enterotoxins. The fimbriae were determined by hemagglutination and slide agglutination tests, enterotoxins—by the use of ileal loop test in piglets (LT and STb enterotoxins) and suckling mouse assay (STa enterotoxin). It was found that 72.8 and 53.0% strains, isolated from diseased suckling and weaned piglets, respectively, possessed specific fimbrial hemagglutinins, in most cases with K88 antigen. Additionally, 987P fimbriae were detected in 14.0 and 0.7% strains isolated from piglets with diarrhea. Only 5 strains (0.7%) recovered from healthy piglets had specific fimbriae, usually with undetermined antigenic structure. F1 fimbriae (called common or unspecific) were found in strains isolated both from diseased (15.2 and 16.3% strains, respectively) and healthy piglets (27.1% strains). It was noted that the strains isolated from suckling and weaned piglets with diarrhea in most cases were enterotoxigenic (90.5 and 69.1% strains, respectively) and most frequently produced heat-labile toxin LT alone or with STb. 18.5% of enterotoxigenic strains isolated from healthy piglets produced STa toxin.  相似文献   

16.
The sensitivity of various cell cultures to heat‐labile enterotoxins (LT) and Verocytotoxin (VT) of fifteen E. coli strains isolated from cases of pig colibacillosis in Poland was estimated and compared with the effect of enterotoxins of four standard E. coli strains. Often tested cell cultures, only the following were susceptible: CHO, Vero, GMK, and HeLa.

Eight strains showed CTE in HeLa and CHO cells and five of these reacted in Vero cells. The results appear to suggest that some of the tested E. coli strains isolated from pigs produced VT enterotoxin. Morphological changes caused by the above mentioned E. coli toxins in Vero and GMK cells took the form of cell rounding, followed by cell dissolution.  相似文献   

17.
腹泻水貂检出携带耶尔森菌HPI毒力岛的大肠杆菌   总被引：3，自引：0，他引：3  
为了解大肠杆菌引起水貂腹泻的机理,进行了小肠结肠炎耶尔森菌HPI毒力岛基因的检测,并对其菌株做毒力试验。用PCR扩增法检测毒力岛基因irp2和fyua,小鼠腹腔注射检测菌株毒力。结果：从3个貂场腹泻病死水貂脏器以及粪便中分离出血清型分别为078、029和038的大肠杆菌,对3个血清型大肠杆菌进行毒力岛检测,均检出携带小肠结肠炎耶尔森菌HPI毒力岛基因irp2和fyua。3个血清型078、029和038的大肠杆菌均使小鼠发病死亡。结果表明水貂腹泻是由携带小肠结肠炎耶尔森茵HPI毒力岛基因irp2和fyua的大肠杆菌引起,该茵对水貂的健康具有潜在的威胁。  相似文献   

18.
A toxoid prepared from the toxin of Vibrio cholera was adjuvanted with aluminium hydroxide and used for immunisation of pregnant gilts. Litters of these and of non-vaccinates were experimentally challenged with Escherichia coli producing either heat labile and heat stable (LT and ST) enterotoxins or ST enterotoxin only. Both the challenge strains of E coli produced high rates of mortality (64 and 68 per cent) and morbidity (80 and 100 per cent) in litters of non-vaccinated dams. Statistically highly significant protection against the LT/ST enterotoxin producing strain of E coli was obtained accompanied by the absence of colonisation of the small intestine by the pathogen. No protection against the ST enterotoxin producing strain was found. It is suggested that this vaccine would not confer passive protection to piglets against K99 and 987-positive E coli which usually produce ST enterotoxin only.  相似文献   

19.
Shiga-like toxin (SLT-IIv) from Escherichia coli strains associated with edema disease of pigs was characterized and compared with SLT-I, SLT-II, and the SLT of E. coli strain HI8 (SLT-HI8). SLT-IIv from an E. coli K12 in which the genes for SLT-IIv had been cloned was indistinguishable from SLT-IIv of wild strains of E. coli from edema disease. There was cross-neutralization among all SLTs except SLT-I. The different SLTs could be distinguished by heat lability, with the descending order of heat lability being SLT-IIv, SLT-II, SLT-I, and SLT-HI8. SLT-IIv and SLT-HI8 had lower cytotoxic titers on HeLa cells compared with Vero cells and were more active on MDBK cells than were the other SLTs. All SLTs were enterotoxic in rabbit but not in pig intestine and SLT-IIv was less enterotoxic than SLT-I. SLT-IIv had a lower LD50 in mice than did the other SLTs.  相似文献   

20.
试验以腹泻仔猪肠道为试验材料,对其肠道内容物进行细菌学检查及分离,对从肠道内容物分离得到的优势菌进行形态特征、生化特性和16S r DNA分子鉴定,判定为大肠杆菌。此菌株对供试的小白鼠有致病性,测其LD50为1.26×107 CFU/只。菌株对供试的氧氟沙星等敏感;对庆大霉素等中度敏感;对林可霉素等耐药。推断此菌株是导致仔猪腹泻致死的主要病原菌。利用病死猪肠道制作自家苗,给产前母猪注射,其后代仔猪腹泻率大幅降低。研究弄清了四川某猪场仔猪腹泻的原因,减少了猪场的经济损失,也为仔猪大肠杆菌病的预防和治疗提供了一定参考,为临床早期合理用药提供一定借鉴。  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号