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1.
Anti-adhesive activities of colostrum and milk from genetically susceptible sows, which protected their susceptible offspring in an outbreak of neonatal diarrhoea caused by K88-positive Escherichia coli, were compared with the activities in mammary secretions of resistant dams that did not protect their susceptible progeny. There was significantly more anti-adhesive antibody in the secretions of susceptible sows than in resistant sows, both during the disease period, and 1 year later. Fractionation of colostrum by gel filtration and ion-exchange chromatography led to identification of the anti-adhesive antibodies as including both IgA and IgM.  相似文献   

2.
The emigration of neutrophils from the blood of neonatal piglets into the intestinal lumen in response to a K88-positive strain of Escherichia coli was investigated. The pig herd used was of known genetic susceptibility to K88-positive E coli and had recently experienced an outbreak of neonatal diarrhoea. Neutrophil emigration depended on certain factors. Neutrophils emigrated into ligated loops in susceptible piglets sucking immune colostrum from susceptible dams but not into loops in colostrum deprived resistant piglets or piglets sucking non-immune colostrum from resistant dams. In susceptible, colostrum deprived piglets neutrophils in intestinal contents were only associated with severe lesions. Large numbers of neutrophils which appeared at several foci on the villi were observed in three of six resistant piglets that sucked immune colostrum from susceptible dams. It was concluded that neutrophil emigration into the intestinal lumen of piglets could occur in response to K88-positive E coli and resulted not from the presence or absence of the intestinal K88-receptor but from the ingestion of immune colostrum.  相似文献   

3.
Investigators have found that oxytetracycline decreases the adhesion of K88+ Escherichia coli to intestinal epithelial cells in vitro. This occurs with oxytetracycline-sensitive E coli at drug concentrations less than those required to prevent growth and with E coli that are resistant to the drug. We conducted experiments to determine whether oxytetracycline alters the disease caused by an oxytetracycline-resistant K88+ enterotoxigenic strain of E coli. Oxytetracycline-treated pigs (inoculated with K88+ E coli) did not differ from nontreated pigs in the incidence or severity of diarrhea, nor in the shedding of K88+ E coli. However, during recovery, weight gain by treated pigs was slower than that of nontreated pigs. The control pigs were not inoculated with E coli, and they remained clinically normal. Oxytetracycline-treated controls gained weight faster than nontreated controls. Some controls were genetically resistant to K88+ E coli, others were susceptible. The K88-resistant oxytetracycline-treated controls gained weight faster than the K88-susceptible oxytetracycline-treated and non-treated controls.  相似文献   

4.
Porcine postweaning Escherichia coli enteritis is a cause of significant morbidity and mortality in pigs worldwide, and effective prevention remains an unsolved problem. This study examined the correlation between susceptibility of pigs to experimental infection with an E. coli F18 strain and the porcine intestinal F18 receptor genotypes. Thirty-one pigs classified as either belonging to the susceptible or the resistant genotype were inoculated with cultures of an E. coli O138:F18 isolated from a pig with postweaning diarrhoea. Susceptibility to colonisation and diarrhoea was assessed by clinical observations, faecal shedding of the challenge strain, histopathology and microscopic adhesion tests. Ten of 14 (71.4%) genetically susceptible pigs and one of 17 (5.9%) resistant pigs developed diarrhoea attributable to the challenge strain. There was no difference in susceptibility between homozygotic and heterozygotic susceptible pigs. Faecal shedding of the challenge strain correlated with the genetic receptor profile. Twenty pigs examined immunohistochemically revealed focal to extensive small intestinal mucosal colonisation by E. coli O138:F18 in nine of 10 susceptible and three of 10 resistant pigs. Results of in vitro adhesion assays performed with F18 cells on enterocyte preparations from 24 pigs, showed complete concordance with the F18 genotypes. In conclusion, this study showed a high correlation between the porcine intestinal F18 receptor genotypes and susceptibility to disease. However, pigs of the resistant F18 receptor genotype were not entirely protected against intestinal colonisation by E. coli F18.  相似文献   

5.
A challenge trial was carried out in which Escherichia coli O157 K88ac was administered to a litter of weaned pigs and the development of the disease monitored over a five-day experimental period. The eight animals in the trial were assigned to two groups depending on whether they exhibited disease symptoms. Six pigs developed diarrhoea and two appeared unaffected; these were designated as the test (or K88-susceptible) group and the control (or K88-resistant) group, respectively. The animals were euthanised and the intestine was removed and sections processed for brush border membrane vesicle preparation. Microscopic and biochemical assays were undertaken on tissue samples from each animal and a strong correlation was observed between the expression of a glycoprotein receptor complex associated with the brush border membrane and the development of disease symptoms. Further investigation revealed the presence of an analogous glycoprotein complex in the K88-resistant group which did not bind the K88-fimbriae antigen. These results suggest that genetic differences in the glycosyl moieties of the receptor complex provide the basis for disease susceptibility to K88-positive E. coli.  相似文献   

6.
We attempted to determine whether weaning is required for induction of diarrhea in pigs with postweaning enterotoxigenic Escherichia coli infection. Three-week-old newly weaned pigs and their suckling littermates were inoculated with the K88+ enterotoxigenic E coli strain M1823B. Fourteen of 21 weaned and 12 of 20 suckling pigs were genetically resistant to intestinal adhesion by the K88+ strain of E coli; they remained healthy, and gained weight at similar rates. Both groups of K88-resistant pigs gained weight faster, and shed fewer bacteria of strain M1823B in their feces, than did their K88-susceptible counterparts. Diarrhea developed in K88-susceptible pigs in the weaned (6 of 7 pigs) and suckling (4 of 8 pigs) groups, and 1 of the 4 affected suckling pigs died from complications resulting from diarrhea. The incidences of diarrhea, weight gain rates, and the numbers of strain M1823B shed in feces of susceptible weaned and suckling pigs were not significantly (P greater than 0.05) different. Diarrhea scores of susceptible weaned pigs were significantly (P less than 0.02) higher than those of susceptible suckling pigs on the second day after inoculation. In this experimental model, it was concluded that weaning is not required for induction of diarrhea, but may modestly increase its severity.  相似文献   

7.
A haemolytic enteropathogenic E. coli (WG) and pig rotavirus were isolated from a field case of postweaning diarrhoea in pigs. Four-week-old gnotobiotic piglets fed on milk diet were found to be extremely susceptible to infection with WG E. coli . Piglets were less susceptible to the infection immediately after the diet was changed from milk to dry food, and were almost completely resistant 4 days after the change to dry food. There was no difference in the clinical response to infection with WG E. coli when the piglets were fed either a high energy diet or low energy diet. Four-week-old piglets fed milk showed mild symptoms of diarrhoea when inoculated with pig rotavirus. Symptoms were more severe when piglets were inoculated immediately after the change from milk to dry food. Piglets inoculated 4 days after the change of diet showed no symptoms of diarrhoea at all. Under the conditions of these experiments the enteropathogenic E. col produced a more serious disease than did pig rotavirus. Infection of 4-week-old gnotobiotic piglets with both agents given sequentially produced a diarrhoeal disease that was more severe than that produced by each agent separately.  相似文献   

8.
One hundred nineteen live neonatal pigs with diarrhea less than or equal to 2 weeks old were euthanatized, and frozen sections of their ilea were submitted to an indirect fluorescent antibody technique to identify K88, K99, and 987P pili (also referred to as F-4, F-5, and F-6 pili, respectively) in Escherichia coli. Ten-centimeter ileal sections were used to determine numbers of lactose-fermenting bacteria. Of 52 pigs in which E coli pili were found, 14 had K88 (27%), 23 had K99 (44%), 13 had 987P (25%), and 2 had K88 and K99 simultaneously (4%). Numbers of lactose-fermenting bacteria were significantly (P less than or equal to 0.05) higher in pigs with piliated E coli than in pigs without piliated E coli. Results of this study indicated that piliated E coli are a major cause of enteric disease in neonatal swine in Michigan, and that in pigs less than or equal to 2 weeks of age, K99 was the most frequently encountered pilus antigen.  相似文献   

9.
The possible role of bacterial adherence in the pathogenesis of experimental mastitis in the mouse was examined with four strains of Escherichia coli. Two of these strains had a known adhesion antigen (K88) and two did not. The K88 antigen did not play a significant role in the virulence or infectivity of E. coli either in the murine or bovine mammary gland. Two E. coli strains, W1 (K88+) and J2 (K88-) were virulent in the mouse but did not adhere to epithelial cells. Both these strains produced clinical mastitis in the cow. A third strain, D282 (K88-), produced mild disease in the mouse but was avirulent in the cow. The fourth strain, 233/ID (K88+), was avirulent in both the mouse and the cow. Strains D282 and 233/1D were killed rapidly by bovine serum whilst J2 and W1 were more resistant. All strains were more sensitive than the control resistant strain E. coli P4, which is known to be highly virulent for the lactating udder.  相似文献   

10.
Experiments were conducted to evaluate the effect of restricted feeding of a starter diet to suckling pigs (creep feeding) in a model of postweaning colibacillosis. The hypothesis that restricted creep feeding primes an intestinal allergic reaction to starter diet ingested after weaning was tested. Twenty-eight suckling pigs were fed a starter diet for 3 h/d on days 7, 8, and 9 after birth (creep-fed). Twenty-six suckling pigs were not fed the diet until 3 weeks of age (not creep-fed), when all pigs were weaned and given the starter diet. One day after weaning, 24 creep-fed and 22 not creep-fed pigs were inoculated with K88+ enterotoxigenic Escherichia coli, and 4 pigs in each group were kept as noninoculated controls. Among inoculated pigs (principals), 10 creep-fed and 12 not creep-fed pigs were found to be genetically resistant to K88+ E coli and remained healthy during the 6-day postinoculation period, as did the noninoculated controls. Eighteen (10 creep-fed and 8 not creep-fed) of the 24 genetically susceptible principals developed diarrhea after inoculation. There were no significant differences in the incidence and severity of diarrhea, amount of body weight loss, and mortality between creep-fed and not creep-fed susceptible principal pigs. Histologic examination of intestine from control pigs and principals that survived for 6 days after infection did not reveal any substantial morphologic difference between creep-fed and not creep-fed groups. In conclusion, creep feeding was not required for the production of diarrhea in this model. Creep feeding did not induce morphologic changes characteristic of an allergic reaction in the small intestine.  相似文献   

11.
The aetiology of neonatal porcine diarrhoea was studied in 15 different herds located in the north-western region of Venezuela. Of 56 strains of Escherichia coli analyzed, 16 (28.6%) were shown to produce heat-stable (STa) enterotoxin, as detected by infant mouse assay. Only four of these STa+ isolates also possessed the K88 pilus antigen, two were 987P+ and none possessed the K99 antigen, leaving 10 STa+ samples in which no pilus antigen was identified. Among the 40 STa negative samples were six K88+ specimens, one K99+, four 987P+, one which reacted as K88+ + K99+ and one K88+ + 987P+. Considering as pathogenic any strain showing at least one of the characters studied, pathogenic E. coli were detected with an overall frequency of 42.9%, being more prevalent during the second week of life. An electrophoretic analysis of the plasmid content of the field isolates of E. coli, revealed the presence of numerous species of extrachromosomal DNA, although no direction association could be made between a particular plasmid and any of the pathogenic characteristics identified. Results of Southern blot analysis indicate that the STa enterotoxin was preferentially encoded within an endemic plasmid of 4.9 Md. Other plasmids present in the E. coli isolates could be related to antibiotic resistance. With the exception of one strain, all E. coli isolates were resistant to more than one of the nine drugs tested; multiresistant E. coli were frequently isolated, including four strains which were resistant to seven antibiotics.  相似文献   

12.
猪肠毒性大肠杆菌 (ETEC)是仔猪黄痢、白痢等腹泻疾病的主要病原菌 ,发病率和死亡率分别占总发病率和死亡率的 5 6 .2 %和 2 4 .7%。按其特异菌毛产生的粘附素不同有 K88、K99、987P等多种类型 ,K88又可分为 ab、ac、ad血清型 ,现已知 ETEC K88能否致病 ,取决于宿主小肠粘膜上皮细胞刷状缘有无受体 ,并受制于 1对等位基因 ,有受体 (敏感型 )为显性 (S) ,无受体 (抗性型 )为隐性 (s)。该位点位于 1 3号染色体长臂 3.1区段 ,与转铁蛋白 (Tf)连锁 (相距7.4 c M) ,且 Tf基因频率与 K88抗性存在一定关系 ,抗性型与敏感型的小肠粘液理化性质也存在差异 ,据此 ,有可能采用生化及分子生物技术筛选抗性遗传标记 ,开展抗病育种。  相似文献   

13.
A vaccine of rotavirus and K99 antigen from enterotoxigenic Escherichia coli was emulsified in oil adjuvant and administered intramuscularly to pregnant cows. Calves born to and reared on vaccinated dams were protected against experimental rotavirus infection at five days old when compared with calves from unvaccinated control cows. Field trials of the vaccine were carried out in 40 commercial herds, in which half the cows in each herd were selected at random for vaccination and half were left unvaccinated. In 31 herds (2641 cows) there was no significant diarrhoea problem (less than 10 per cent morbidity); these herds were excluded from further analysis. The nine remaining herds did experience a calf diarrhoea problem of greater than 10 per cent morbidity, but on four farms the disease was associated with cryptosporidiosis and on a fifth no enteropathogens were detected; these five farms (461 cows) were also excluded from further analysis. Of the remaining four herds, two beef suckler herds (105 cows) had concurrent rotavirus and cryptosporidial infections, and vaccination was associated with a decreased excretion of rotavirus but not with a decreased incidence of diarrhoea. In the other two dairy herds (68 cows) with prevaccination rotavirus problems, there was a significantly decreased incidence of diarrhoea in calves born to vaccinated cows. No natural field challenge of enterotoxigenic E coli was encountered on any of the trial farms.  相似文献   

14.
A reproducible model of postweaning colibacillosis was obtained by controlling management and environmental variables to simulate conditions often seen at weaning. Suckling pigs were exposed briefly to starter diet at 1 week of age, weaned at 3 weeks of age, held at an ambient temperature of 20 +/- 2 C, and again given the starter diet. One day after weaning, each pig was given 10(10) colony-forming units of enterotoxigenic Escherichia coli strain M1823B (O157:K88ac:H43-LT+ STb+) in broth containing 1.2% sodium bicarbonate via stomach tube. In vitro adhesion by strain M1823B to isolated intestinal branch borders was used to test pigs for susceptibility to K88. In this model, 3 syndromes were induced in susceptible pigs: (1) peracute fatal diarrhea; (2) moderate diarrhea, weight loss, and fecal shedding of the inoculum strain; and (3) no diarrhea, weight loss, and fecal shedding of the inoculum strain. Rotavirus particles were not found in fecal specimens of pigs with diarrhea. The K88-susceptible, noninoculated control pigs remained clinically normal. It was concluded that susceptibility to adhesion by K88+ enterotoxigenic Escherichia coli was a requirement for the production of disease in this model; inoculation with rotavirus was not necessary.  相似文献   

15.
The results of our study suggest the in vivo transfer of Hly plasmid from native pathogenic and enterotoxigenic Escherichia coli strain to autochtonous Escherichia coli, using ileal loop test. To confirm this hypothesis pHly::Tn5 and PHly::Tn3 were obtained using an in vitro recombination method, and introduced to Escherichia coli laboratory strain. For experiments the laboratory strain, carrying pHly::Tn5 and pHly::Tn3 and pHly::Tn5 strain which acquired K88(F4) by means of conjugation, were used. In the study in which the donor Escherichia coli pHly::Tn5 strain, carrying antigen K88(F4), was injected into the ileum, pHly conjugants were isolated from faeces after 48 h in 2 out of 5 pigs, which was a low frequency. After the oral introduction of 10(9) cells of pHly::Tn5 and pHly::Tn3 Escherichia coli strains without the colonizing factor K88(F4), conjugants were not isolated from faeces of experimental animals. However when the pigs received donor CSH55 pHly::Tn5 Escherichia coli strain orally, which were also carrying plasmid K88(F4), transconjugants were obtained in a low frequency of 3 out of 9 pigs. Our experiments confirmed the suggestion of Smith that in vivo transfer of plasmid in the intestine of animals is only possible when the donor transfers the plasmid with high frequency and readily colonizes the intestine. The pHly::Tn5 plasmid acquired by in vitro recombination does not spread with time throughout the autochtonic population of Escherichia coli present in the intestine of swine. The results of our study showed the in vivo transfer in pigs intestine of Hly pathogenicity marker from both native pathogenic strains carrying antigen K88(F4) and constructed donor laboratory strain of Escherichia coli pHly::Tn5 also carrying antigen K88(F4) to autochtonous intestinal strains.  相似文献   

16.
The effect of creep feeding on the response of pigs weaned at two or three weeks old to infection with an enteropathogenic strain of Escherichia coli (O149; K91[B], K88 a, c [L]) was studied in two separate experiments. Gastric intubation was adopted to regulate the intake of creep feed during the sucking period. Animals were given the enteropathogenic strain either before weaning or at weaning and the course and outcome of the infection followed bacteriologically and clinically. The response of the animals to the infection varied considerably in accord with recent reports of multiple phenotypes (to K88 +ve organisms) among pigs but consumption of creep feed before weaning did not significantly affect the prevalence, duration or severity of the diarrhoea induced experimentally by the organism. Hence reputed immunological responses mounted against dietary antigens did not predispose to or protect against this infection.  相似文献   

17.
Three-week-old weaned and colostrum-deprived neonatal (less than 1 day old) pigs were inoculated to determine the pathogenicity of 2 enterotoxigenic Escherichia coli isolates that do not express K88, K99, F41, or 987P adhesins (strains 2134 and 2171). Strains 2134 and 2171 were isolated from pigs that had diarrhea after weaning attributable to enterotoxigenic E coli infection. We found that both strains of E coli adhered in the ileum and caused diarrhea in pigs of both age groups. In control experiments, adherent bacteria were not seen in the ileum of pigs less than 1 day old or 3 weeks old that were noninoculated or inoculated with a nonpathogenic strain of E coli. These control pigs did not develop diarrhea. Antisera raised against strains 2134 and 2171 and absorbed with the autologous strain, grown at 18 C, were used for bacterial-agglutination and colony-immunoblot assays. Both absorbed antisera reacted with strains 2134 and 2171, but not with strains that express K99, F41, or 987P adhesins. A cross-reaction was observed with 2 wild-type K88 strains, but not with a K12 strain that expresses K88 pili. Indirect immunofluorescence with these absorbed antisera revealed adherent bacteria in frozen sections of ileum from pigs infected with either strain. We concluded that these strains are pathogenic and express a common surface antigen that may be a novel adhesin in E coli strains that cause diarrhea in weaned pigs.  相似文献   

18.
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   

19.
The presence of the astA gene responsible for production of enteroaggregative Escherichia coli heat-stable enterotoxin 1 (EAST1) was examined in E. coli strains isolated from pigs with postweaning diarrhoea. Two hundred and seven isolates were tested using PCR for the astA marker and for heat-labile I (LTI), heat-stable I (STI), and heat-stable II (STII) enterotoxin genes. Moreover, the isolates were also analysed for their serotypes (O and K antigens) as well as for fimbrial adhesins using agglutination methods. It was shown that 96 (46.4%) of the isolates possessed the astA genetic determinant. The most common EAST1-positive E. coli serotype was O149:K91 and these strains were mostly LTI/STII-positive. A close correlation between the presence of F4 fimbriae and the EAST1 gene was also observed: 88 of 96 (91.7%) astA(+) isolates tested possessed the F4 antigen. Thus, EAST1 enterotoxin may represent an additional virulence determinant playing a role in the pathogenesis of porcine colibacillosis.  相似文献   

20.
A vaccine was prepared using recombinant DNA techniques to prevent fatal enterotoxigenic Escherichia coli diarrhea in swine. The product, which is a subunit vaccine, was prepared by mechanical and chemical removal of pilus adhesins from the surface of genetically engineered strains of E. coli. The vaccine contains the pilus adhesins K88, K99, and 987P plus an adjuvant. The genes responsible for production of K88 and K99 were separately cloned into the multicopy vector pBR322. K88 was found to be encoded on a 7.6-kilobase HindIII-EcoRI fragment, and K99 was found to be encoded on a 7.15-kilobase BamHI fragment. Strains containing the recombinant plasmid for K99 produced up to ten times more K99 than strains containing the wild-type plasmid. Vaccination of pregnant pigs with the vaccine led to production of pilus-adhesin-specific antibodies that were transferred to the piglets in colostrum and milk. Pilus-adhesin-specific antibodies neutralized the adhesiveness of the pili on enterotoxigenic E. coli, thus preventing attachment, colonization, and disease. Mortality of pigs in litters from vaccinated pigs due to experimentally induced enterotoxigenic E. coli diarrhea was reduced 10-to-20-fold (depending upon the challenge strain), and the incidence, severity, and duration of diarrhea were also reduced.  相似文献   

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