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1.
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   

2.
A total of 476 Escherichia coli isolated from weaned pigs with diarrhea and/or edema disease were screened for the presence of the enteroaggregative E. coli heat-stable enterotoxin 1 (EAST1) gene by polymerase chain reaction (PCR). E. coli strains that carried EAST1 genes were also tested by PCR for the presence of genes for five fimbriae (F4, F5, F6, F18 and F41), two heat-stable (STa and STb) and one heat-labile (LT) enterotoxin, and Shiga toxin 2e (Stx2e). One hundred and forty nine (31.3%) of the 476 E. coli isolates carried the gene for EAST1. Of these 149 isolates, 66 (44.3%) carried the east1 gene only and 83 (55.7%) carried genes for the fimbrial adhesins or enterotoxins. E. coli which carried east1 gene also possessed genes for STa or F4 frequently. EAST1 may represent an additional determinant in the pathogenesis of E. coli diarrhea in weaned pigs.  相似文献   

3.
The study comprises fifty 4 to 12 weeks old pigs that died from oedema disease or severe diarrhoea. Smears were prepared from the mucosa of duodenum, jejunum and ileum, and by immunofluorescence F107 fimbrial antigens were detected. E. coli. strains were isolated from the intestines and were characterised by slide agglutination (serogroup and F107 fimbriae production), by their cytotoxicity for Vero cells, and by gene amplification (genes coding for the major F107 subunit FedA, the toxin causing oedema disease SLT-IIv, and enterotoxins LTI, STIa and STII). F107 fimbriae were demonstrated in association with E. coli of serogroups O139:K12 and O141:K85a,b but not of serogroup O149:K91:F4a,c. Expression in culture of F107 fimbriae by some isolates gave additional evidence for production of these fimbriae by ETEC strains. The genetic determinant of SLT-IIv was found in association with F107, and could not be detected in serogroup O149:K91:F4a,c. Gene fedA was demonstrated in two isolates which were devoid of SLT-IIv. Most isolates from cases of oedema disease belonged to serogroup O139:K12 and did not contain enterotoxin genes. Isolates from pigs that suffered from diarrhoea were serotyped O141:K85a,b or O149:K91:F4a,c, and carried at least two enterotoxin genes in their genomes. In a small proportion of the cases F107 antigens were demonstrated in intestinal smears although gene fedA was not detected in the corresponding isolates. The results confirm the importance of F107 fimbriae as virulence factor in oedema disease E coli strains, but also demonstrate that F107 fimbriae can be found in association with postweaning diarrhoea isolates. In these latter strauns enterotoxins were always demonstrated, irrespective of the presence of toxin SLT-IIv.  相似文献   

4.
This study was undertaken to determine the present distribution of serogroups, hemolytic activity and virulence factors among Escherichia coli strains isolated from pigs with postweaning diarrhoea from eight provinces in eastern China. Two hundred and fifteen E. coli isolates were serogrouped with O-antisera, investigated for hemolytic activity, assessed for F4, F5, F6, F18 and F41 fimbrial antigens by monoclonal antibodies and detected for genes of enterotoxins and shiga-toxin-two-variant (Stx2e) by a multiplex polymerase chain reaction (PCR). Among these E. coli isolates, 140 were determined to be placed in serogroups, 52 were unable to be serogrouped and the rest 23 auto-agglutinated. These isolates distributed in 45 serogroups and 64.3% (90/140) belonged to 12 O serogroups: O8, O9, O11, O20, O32, O91, O93, O101, O107, O115, O116 and O131. Hemolytic activity was detected in 11.6% (25/215) of all isolates. Several uncommon O serogroups were discovered in this study. Agglutination tests showed that 50.2% (108/215) of these isolates were positive for one or more of the five fimbrial antigens. Seventy-two E. coli strains expressed single fimbria and 36 strains expressed two or more fimbriae. Among these 215 E. coli isolates, strains expressing F18, F4, F6, F6 + F18 or F5 + F41 occurred more frequently. PCR analysis showed that 60.5% (130/215) of the isolates only harboured the gene of estI (STI) while 6.0% (13/215) strains possessed the genes of stx2e, estI and estII and 5.6% (12/215) of strains had the genes of estI/estII. Of all these isolates, 107 (49.8%) were negative for the fimbrial antigens examined. The fimbria-negative isolates usually possessed genetic determinant of estI (78, 72.9%).  相似文献   

5.
E. coli strains isolated from pigs with postweaning diarrhea or edema disease were tested by phenotypic and genotypic methods for the presence of virulence antigens and genes, respectively. The slide agglutination and ELISA analyses were used for determination of F4, F5, F6, F17, and F41 fimbriae whereas the prevalence of fimbrial fedA and toxin eltI, estI, estII, stx1, stx2 and stx2e genes were recorded by the means of PCR. Only F4 antigen (ac variant) was found in strains of the serogroup O149:K91 isolated from pigs with diarrhea. PCR analyses showed that the fedA gene encoding F18 fimbriae was present in 61.9% of strains isolated from pigs with diarrhea and in 84.2% of strains isolated from pigs with edema disease. The eltI genes encoding heat-labile toxin I (LTI) were present only in 9 out of 21 strains recovered from pigs with diarrhea. Shiga toxin 2 variant (stx2e) genes were found in six isolates from edema disease and also in one strain from diarrhea. The PCR test used in the study was a sensitive and valuable method for determination of virulence factors of E. coli strains.  相似文献   

6.
Enterotoxigenic Escherichia coli (ETEC)-associated post-weaning diarrhea (PWD) is economically one of the most important diseases for the swine industry. Porcine ETEC strains typically express K88 or F18 fimbria and heat-labile (LT) and/or heat-stable (STa, STb) enterotoxins. However, recent studies indicate that EAST1 toxin, adhesin involved in diffuse adherence (AIDA-I) and porcine attaching and effacing-associated factor (paa) may also be expressed by ETEC strains associated with diarrhea. To better understand the virulence factors of E. coli strains that cause PWD, we applied PCR to screen for K88, F18, F41, 987P and K99 fimbrial genes; LT, STa, STb, Stx2e and EAST1 toxic genes; and AIDA-I, paa and EAE adhesin genes in E. coli strains recently isolated from young pigs with PWD in the US. Of 304 E. coli isolates from diarrheic pigs submitted for testing, 175 (57.6%) strains possessed fimbrial genes: K88 (64.6%), F18 (34.3%), F41 (0.57%), K99 (0.57%), 987P (0); toxin genes: LT (57.7%), STb (72.6%), STa (27.4%), STx2e (17.4%), EAST1 (35%); and adhesin genes: AIDA-I (26.9%), paa (60%), EAE (1.1%). All toxin genes except the EAST1 toxin gene, were almost exclusively associated with K88+ or F18+ isolates, and most of these isolates carried multiple toxin genes. The non-fimbrial adhesin paa was found present in over half of the K88+ isolates. A total of 129 (42%) isolates carried no fimbrial genes, including 66 (21.7%) isolates that did not have any of the above virulence genes. These results suggest a broad array of virulence genes associated with PWD in pigs.  相似文献   

7.
A total of 604 Escherichia coli strains isolated from weaned pigs with diarrhea or edema disease on 653 swine farms were screened for the presence of the adhesin involved in diffuse adherence (AIDA) gene by polymerase chain reaction (PCR). Escherichia coli isolates that carried AIDA genes were also tested by PCR for the detection of 5 fimbriae (F4, F5, F6, F18, and F41), 3 heat-stable (STa, STb, and EAST1) and 1 heat-labile (LT) enterotoxin, and Shiga toxin 2e (Stx2e) genes. Forty-five (7.5%) of the 604 E. coli isolates carried the gene for AIDA. Of these 45 isolates, 5 (11.1%) carried EAST1 genes only, 1 (2.2%) carried genes for at least one of the fimbrial adhesins, 12 (26.7%) carried genes for at least one of the toxins, and 27 (60%) carried genes for at least one of the fimbrial adhesins and toxins. Fifty-one percent of strains that carried AIDA genes carried Stx2e genes, and 40% of strains that carried AIDA genes carried F18ab. The isolation rate of enterotoxigenic E. coli strain carrying genes for AIDA was 87%, and the isolation rate of Shiga toxin-producing E. coil strain carrying genes for AIDA was 49%. AIDA may represent an important virulence determinant in pigs with postweaning diarrhea or edema disease.  相似文献   

8.
The OK antigens and the fimbriae F4 of E. coli with haemolysis isolated from 113 cases of oedema disease and/or diarrhoea were identified serologically. The genes for F18 and for enterotoxins LT, STIa and STII as well as Shigatoxin Stx2e were determined by PCR. Fimbrial variants F18ab and F18ac were distinguished by means of indirect immunofluorescence on smears prepared from the intestinal mucosa and from cultures grown under appropriate conditions. Adhesive fimbriae were detected with every case or isolate, respectively, by means of at least one out of the techniques mentioned above. The serogroup O149:K91 with fimbriae F4ac (K88ac) and genes for the enterotoxins LT and STII was most prevalent. Serogroup O139:K12 with fimbriae F18ab and the gene for Stx2e was second, whereas serogroups O141ab and O141ac with fimbriae F18ac and genes for Stx2e, STII and often LT were much less prevalent. The serogroup O147:K89 with fimbriae F18ac, and genes for STIa and STII was detected for the first time in Switzerland.  相似文献   

9.
A total of 1002 Escherichia coli strains isolated from pre-weaned pigs with diarrhoea on 1114 swine farms were screened for the presence of the adhesin involved in diffuse adherence (AIDA) gene by polymerase chain reaction (PCR). Escherichia coli isolates that carried AIDA genes were also tested by PCR for the detection of five fimbriae (F4, F5, F6, F18 and F41), heat-stable (STa, STb) and heat-labile (LT) enterotoxin, enteroaggregative E. coli heat-stable enterotoxin 1 (EAST1), and Shiga toxin 2 oedema disease (Stx2e) genes. Twenty-three (2.3%) of the 1002 E. coli isolates carried the gene for AIDA. Among 23 isolates shown to carry genes for AIDA, three carried the AIDA gene as the only shown virulence factor. Other isolates carried other virulence factor genes in addition to AIDA. Four isolates carried genes for at least one of the fimbrial adhesins and enterotoxins. Sixteen isolates carried genes for enterotoxins only. The AIDA may represent an additional virulence determinant in pre-weaned pigs with diarrhoea.  相似文献   

10.
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   

11.
Fecal Escherichia coli isolates (n = 3,218) from piglets with edema disease or diarrhea were screened for the genes of Stx2 and Stx2 variants. A total of 283 E. coli isolates (8.8%) proved exclusively positive for Stx2e and most of these (85.1%) harbored genes for F18 fimbria. No recognized adhesins were detectable in 14.5% of the isolates. Genes for heat-stable or heat-labile E. coli enterotoxins were found in F18+ as well as F18 isolates (51.9% and 33.3%, respectively). Five isolates also harbored fyuA and irp2 genes which are indicative of a high pathogenicity island in E. coli. All Stx2e+ isolates lacked genes for intimin, EHEC hemolysin, STEC autoagglutinating adhesin, subtilase cytotoxin, serine protease Espl. The majority of Stx2e+ isolates belonged to phylogenetic groups A (59.3%) and D (38.9%) and only few isolates were classified as B1 and B2 (1.8%). The results suggest that Stx2e-producing E. coli strains are highly prevalent in diseased pigs in Germany. Despite their significant diversity, most strains possess all typical features (Stx2e, F18) of porcine edema disease E. coli. However, a considerable portion of porcine strains resembles published human Stx2e+ strains in that they lack any recognized pig-associated adhesin. Thus, a zoonotic potential cannot be excluded for these strains.  相似文献   

12.
A total of 1002 Escherichia coli strains isolated from pre‐weaned pigs with diarrhoea on 1114 swine farms were screened for the presence of the adhesin involved in diffuse adherence (AIDA) gene by polymerase chain reaction (PCR). Escherichia coli isolates that carried AIDA genes were also tested by PCR for the detection of five fimbriae (F4, F5, F6, F18 and F41), heat‐stable (STa, STb) and heat‐labile (LT) enterotoxin, enteroaggregative E. coli heat‐stable enterotoxin 1 (EAST1), and Shiga toxin 2 oedema disease (Stx2e) genes. Twenty‐three (2.3%) of the 1002 E. coli isolates carried the gene for AIDA. Among 23 isolates shown to carry genes for AIDA, three carried the AIDA gene as the only shown virulence factor. Other isolates carried other virulence factor genes in addition to AIDA. Four isolates carried genes for at least one of the fimbrial adhesins and enterotoxins. Sixteen isolates carried genes for enterotoxins only. The AIDA may represent an additional virulence determinant in pre‐weaned pigs with diarrhoea.  相似文献   

13.
Polymerase chain reaction for 4 fimbriae (F4, F5, F6, F41), 2 heat-stable enterotoxins (STa, STb), and 1 heat-labile enterotoxin (LT) were performed on 400 Escherichia coli isolates to determine their genotype prevalence among enterotoxigenic E. coli isolates from preweaned pigs with diarrhea in the Republic of Korea. A total of 200 of the 400 E. coli isolates were also selected for characterization of the O serogroup. Of these 200 isolates, serogroup could be determined in 139 (69.5%) but not in 61 isolates (30.5%). Isolates of serogroup O101 were the most common, followed in descending order by 08, 020, 0162, 0141, and 0149. Ninety-seven (24.3%) of the 400 E. coli isolates carried genes for at least 1 of the entertoxins or fimbrial adhesins. Of these 97 isolates, 27 carried genes for at least 1 of the fimbrial adhesins and entertoxins. Sixty-six percent of the isolates that carried fimbrial adhesin genes carried genes for at least 1 of the enterotoxins, and 71% of the isolates that carried enterotoxin genes carried genes for at least 1 of the fimbrial adhesins. Genes for the F6 fimbriae were detected in 6% of the E. coli isolates, and F4+, F41+, and F5+ genes were detected in 4.3%, 3.3%, and 2% of the isolates, respectively. Genes for STa, STb, and LT were detected in 10%, 8.5%, and 4.3% of the isolates, respectively. The 6 major genotypes observed in this study (in decreasing order) were F6+, STb+, F41+, STa+STb+, F6+STa+, and STa+.  相似文献   

14.
The presence of the fedA (gene coding F18 fimbriae) and genes coding STa and LTI enterotoxins and verotoxin Stx2v was determined in 30 E. coli strains isolated from weaned pigs with postweaning diarrhea (PWD) and edema disease (ED). The fedA gene was detected in 22 strains (73.3%). It was mostly associated with the presence of ST gene determinant (14 from 22 fedA positive strains, 63.6%). Two strains possessed ST/Stx2v or LTI/Stx2v combination of genes for both toxins and two strains were negative for investigated toxin determinants. Among 8 fedA-negative strains, five strains without gene determinants for toxins were detected. All 30 E. coli strains were investigated for their binding to crude intestinal mucin of a weaned pig fixed in wells of microtitre plates. Positive mucin binding was observed in most of strains, however, great differences were shown between individual strains. Nineteen strains were classified as strongly adherent, 10 strains as weakly adherent, and only one nonadherent strain was found. Three E. coli strains, selected among the best mucin binders, bound to mucin in a concentration-dependent manner. A high mucin binding by E. coli strains was observed only after their cultivation on blood agar plates. Their cultivation in LB broth or on McConkey agar plates had negative effect on the mucin binding by these strains. The mucin binding is not restricted by the presence of fedA gene because the strains displaying very good binding are found either among fedA positive (1, 602/2, 4/3, 576/6) or fedA negative (DK 6, DK 8) E. coli strains. E. coli strains with the highest mucin binding ability belong to potential ST producents (strains 1, 602/2, 4/3, 6/2, 602/4) while the strains without genes coding toxin production displayed lower binding to mucin substratum with exception of the strains ZV5 and 13.  相似文献   

15.
Strains of Escherichia coli (n = 390) isolated from 132 healthy, 4-8-week old calves, were tested by polymerase chain reaction (PCR) for the eae (intimin) gene and shiga toxin genes (stx1 and stx2). All strains were also analysed for F5, F17 and F41 fimbriae and for the heat-labile (LT) and heat-stable (STI and STII) genetic markers. Overall, the eae gene was detected in 84 (21.5%) of the strains tested. Only 21 (5.4%) isolates were positive for stx1 (18 strains) or stx2 (three strains); nine of the stx1-positive isolates also possessed the eae gene. A high percentage (29.2%) of the isolates tested expressed F17 but no enterotoxin genes were detected. None of the eae- or stx-positive strains belonged to the O157 serogroup.  相似文献   

16.
一规模化猪场断奶仔猪腹泻大肠杆菌毒力因子的检测   总被引：3，自引：1，他引：3  
从疑似断奶仔猪腹泻的仔猪中分离、鉴定出15株病原性大肠杆菌。经O血清型鉴定,11株为0131、4株未定型,所有O131血清型菌株呈β溶血。多重PCR检测毒素基因(STa、STb、LT、SLT-2e)和大肠杆菌粘附素单抗(F4、F5、F6、F41、F18)检测菌毛,O131菌株的毒素为STa、STb、SLT-2e,表达F18粘附素,未定型菌株的毒素为STa,共表达F6和F18粘附素。对15株大肠杆菌用16种抗生素进行药敏试验,结果表明:分离株对阿米卡星、痢特灵、新霉素敏感,而对多种抗生素产生了不同程度的耐药性。运用本场大肠杆菌分离株灭活苗免疫猪群,取得良好效果。  相似文献   

17.
Faecal samples from 132 healthy, 4–8‐week‐old calves from four different farms were examined for necrotoxigenic Escherichia coli (NTEC) producing the cytotoxic necrotizing factors type 1 (CNF1) and type 2 (CNF2). CNF2 genes were detected by polymerase chain reaction in 24 (6.1%) of the 396 E. coli strains tested; these strains were found in 18 (13.6%) calves used in the study. None of the 396 E. coli isolates examined possessed the gene encoding CNF1. Overall, 28.8% of E. coli examined expressed the F17 fimbrial antigen. A strong association between CNF2 toxin and F17 fimbriae was found (62.5% of CNF2‐positive strains were F17‐positive). Moreover, six out of 24 NTEC strains had the Stx1 or the Stx2 shiga toxin genes, and three additional isolates possessed the eae genetic marker of the intimin protein.  相似文献   

18.
Ninety-two Escherichia coli isolates from 14 to 28-day-old piglets that died because of diarrhoea were examined for genes for fimbriae (F4, F5, F6, F18 and F41), enterotoxins (STa, STb and LT), verotoxin (VT2e or Stx2e) and enteroaggregative heat-stable enterotoxin 1 (EAST1) by polymerase chain reaction. Twenty-two strains (24%) carried a gene for F4, whereas genes for F18, F6 and F5 + F41 were detected in 10.8, 3.3 and 1.1% of strains respectively. Genes for STb, LT, STa and Stx2e were detected in 40.2, 26.1, 14.1 and 1.1% of strains respectively. The astA gene was detected in 49 (53.3%) isolates, 35 of which also carried genes for enterotoxins and/or fimbriae. The major genotypes reached at (in decreasing order of prevalence) were F4/STb/LT/EAST1, F18/STa/STb/EAST1, STb/EAST1, F6/STa/STb/EAST1 and F18/STb/EAST1.  相似文献   

19.
A total of 720 Escherichia coli strains isolated from diarrheic piglets on 756 swine farms were screened for the presence of the enteroaggregative E. coli heat-stable enterotoxin 1 (EAST1) gene by polymerase chain reaction (PCR). Escherichia coli strains that carried EAST1 genes were also tested by PCR for the presence of 4 fimbriae (F4, F5, F6, F41), 2 heat-stable enterotoxins (STa and STb), and 1 heat-labile enterotoxin (LT) gene. One hundred sixty-four (22.7%) of the 720 E. coli isolates carried genes for EAST1. Of these 164 isolates, 62 (37.8%) carried EAST1 genes only, 11 (6.7%) carried genes for at least 1 of the fimbrial adhesins, 51 (31.1%) carried genes for at least 1 of the enterotoxins, and 40 (23.8%) carried genes for at least 1 of the fimbrial adhesins and enterotoxins. Forty-six percent of strains that carried EAST1 genes carried STa genes, and 16% of strains that carried EAST1 genes carried F4. The isolation rate of enterotoxigenic E. coli strains carrying genes for EAST1 gene was 63%. The 6 major genotypes observed in this study (in decreasing order) were EAST1+, EAST1+STa+, EAST1+STa+STb+, EAST1+STa+F5+, EAST1+STa+F4+, and EAST1+STb+F4+. EAST1 is widely prevalent among diarrheagenic strains of E. coli and may represent an important virulence determinant in the pathogenesis of enteric colibacillosis of preweaned pigs.  相似文献   

20.
Cheng D  Sun H  Xu J  Gao S 《Veterinary microbiology》2006,115(4):320-328
Fimbriae, toxins and pathogenicity islands (PAIs) are main virulence factors of the pathogenic Escherichia coli strains. To investigate into their prevalence in clinical E. coli isolates associated with porcine postweaning diarrhea (PWD) and/or pig edema disease (ED), 240 isolates were obtained from diseased piglets (140 from PWD, 76 from ED and 24 from ED/PWD) and submitted to PCR detection for genes coding for fimbriae, enterotoxins, shiga toxins, intimin and high-molecular-weight protein 2 (HMWP2). Among the 240 isolates detected, detection rates of the genes for F18, F4, intimin, HMWP2, Stx2e, LTa, STa and STb were 26.25%, 3.75%, 28.33%, 16.67%, 35%, 10.83%, 14.58% and 9.17%, respectively, and 67.92% of the isolates could be assigned into 20 different virulence factor patterns. Further more, F18ab+ STEC are the prevalent pathogens of ED, and F18+ and/or intimin+ STEC/ETEC are the dominant pathogens of ED/PWD, while F18ab+, F4+ and/or intimin+ ETEC and HPI+ and/or LEE+ E. coli are more frequently associated with PWD.  相似文献   

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