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1.
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   

2.
This study determined the prevalence of F4, F5, F6, F17 and F41 fimbriae and the genes for FedA (F18 fimbriae), LT and ST enterotoxins, and Shiga toxins Stx1, Stx2 and Stx2e among E. coli isolated from 372 weaned pigs with diarrhea and 46 healthy pigs of the same age. Agglutination tests showed that most isolates were negative for all five fimbrial antigens. The F4 antigen was found in 71 (19.1%) and the F5, F6, or F41 antigen was detected in 6.4% of isolates from diseased pigs. Genes for the F18 fimbriae were detected in 10 (2.7%) strains from diarrheic pigs and in 1 of 46 isolates from healthy pigs. Most isolates (213, 57.3%) from pigs with diarrhea were positive for LTI only or for LTI and STI or Stx2e toxin genes. Fifteen strains (13.7%) possessed only the STI or STII toxin genes. All F4-positive bacteria had genes for LTI or LTI and STI, whereas F18-positive isolates had genes for LTI, LTI/STI, or LTI/Stx2e. Of the strains isolated from diseased pigs, 264 (71.0%) were negative for the fimbrial antigens (genes) examined in this study. The fimbria-negative isolates frequently possessed genetic determinants for LTI (118, 31.7%) or for STII (16, 4.3%) enterotoxins.  相似文献   

3.
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   

4.
Two hundred and fifty Escherichia coli isolates from diarrhoeic and healthy piglets were serotyped and tested for the presence of virulence genes for fimbriae, intimin, heat-labile (LT) and heat-stable (STa and STb) enterotoxins, Stx toxins, and enteroaggregative heat-stable 1 (EAST1) enterotoxin by polymerase chain reaction (PCR). Although 220 isolates from diarrhoeic piglets belonged to 43 O serogroups and 77 O:H serotypes, 60% were of one of the 10 serogroups O2, O8, O15, O54, O84, O101, O141, O147, O149 and O157, and 60% belonged to only 10 serotypes (O8:H-, O54:H-, O84:H7, O101:H-, O141:H-, O141:H4, O147:H-, O149:H10, O163:H-, and ONT:H-). PCR showed that 79% of 220 isolates carried genes for at least one of the virulence factors tested. The gene encoding for EAST1 was the most prevalent (65%) followed by those encoding for STb (49%), LT (42%), STa (13%), and Stx2e (4%). Eighty-three (38%) of the 220 E. coli isolates carried the gene for F4 (K88), whereas genes for F18, F5 (K99), F41, F6 (P987), F17, and intimin (eae) were detected in 9%, 3%, 3%, 3%, 1%, and 3%, respectively. Seropathotype O149:H10:F4:LT/STb/EAST1 (70 isolates) was the most common, representing 32% of isolates. Pulsed-field gel electrophoresis (PFGE) analysis with XbaI of 15 O149:H10 representative isolates from diarrhoeic piglets distinguished 14 types. The 15 isolates exhibited a wide variability of distinct restriction patterns though all belonged to the same serotype (O149:H10), and all but one showed identical virulence determinants (F4, LT, STb, and EAST1). Among 30 isolates from healthy piglets only two virulence genes were detected: EAST1 (26%) and eae (17%). In total, 12 isolates were positives for the eae gene: five isolates had intimin beta1, four possessed intimin theta and three showed intimin type xiB. This is believed to be the first study describing the presence of intimin type xiB in E. coli of porcine origin.  相似文献   

5.
DNA gene probes specific for genes encoding heat labile enterotoxin (LTI), heat stable enterotoxins (STIa, STII), vero cytotoxins (VT1, VT2), and adhesins K88 (F4), K99(F5), F41 and 987P(F6) were used to examine 873 isolates of E. coli from cases of diarrhoea (680 from pigs, 187 from cattle and six from sheep). A total of 188 were toxin gene positive and of these 84 belonged to the classical ETEC serogroups. Of the other 104 toxin gene positive strains, 80 hybridized with the VT2 probe of which 34 were from cases of porcine post-weaning diarrhoea belonging to serogroup 0138:K81 and 22 were untypable strains from cattle.  相似文献   

6.
The objectives of the research were to determine the presence of the gene sequences for Shiga Toxin 2e (Stx2e), enterotoxins (ST-I, ST-II and LT-I), and F18 fimbriae in 144 Escherichia coli strains isolated from pigs with edema disease; to assess the ability of stx2e(+) strains to produce Stx2e; and to determine the O serogroups of the E. coli strains. Presence of the genes was determined by polymerase chain reaction (PCR), production of Stx2e was assessed by cytotoxicity for Vero and Hela cells, O serogroups were identified by agglutination with specific antisera. Of the 144 strains tested, 99 were stx2e(+) by PCR, but only 45 of these were Stx2e(+) in the cell culture assays. Among the 99 stx2e(+) strains, PCR detected the genes for F18ab, ST-I, ST-II, LT-I in 76, 40, 31 and 16 strains, respectively. Forty-one of the 99 sxt2e(+) strains belonged to O group 139; the rest did not belong to the classical edema disease O serogroups. It is likely that the enterotoxins, whose genes were detected at high frequency, are responsible for diarrhea seem in pigs with edema disease in Brazil.  相似文献   

7.
A PCR was used to determine the genotypic prevalence of five fimbrial adhesins (F4, F5, F6, F41 and F18), two heat-stable enterotoxins (STa and STb), the heat-labile enterotoxin (LT), and the shiga toxin 2e (Stx2e) in 230 isolates of Escherichia coli from postweaning pigs with diarrhoea or oedema disease. Ninety-four (40.9 per cent) of the isolates carried genes for at least one of the fimbrial adhesins or toxins. Genes for the F18 fimbrial adhesin were detected in 18.3 per cent, and genes for F4, F6, F5 and F41 were detected in 10.0 per cent, 4.3 per cent, 1.7 per cent and 0.8 per cent of the isolates, respectively. Genes for STa, STb and LT were detected in 25.7 per cent, 15.2 per cent and 8.7 per cent of the isolates, respectively. Genes for Stx2e were detected in 36 (15.6 per cent) of the isolates, and among them 24 also contained the gene for F18ab and four also contained the gene for F18ac.  相似文献   

8.
Duplex real-time PCR assays were used as modules to cover partially automated detection of 12 genes encoding adhesins, enterotoxins and Shiga toxins in faecal E. coli isolates. For this a total of 194 E. coli isolates from pigs suffering from post-weaning diarrhoea (PWD), including 65 isolates with haemolytic activity, and 83 isolates from calves with diarrhoea were examined. Data obtained by PCR were compared with O-typing and with haemolytic activity as indirect virulence markers. E. coli O-types O139:K82, O141:K85, and O149:K91 accounted for 43.8% (n = 85) of all porcine strains and for 55.4% (n = 36) of the porcine strains, which exhibited haemolytic activity. These strains carried virulence genes by 65.9% (n = 56) and 80.6% (haemolytic E. coli, n = 29), respectively. The E. coli O-types O139:K82 and O141:K85 were significantly associated with the adhesin gene F18, and O149:K81 with the F4 gene. In this context, detection of the gene encoding F18 was coupled predominantly with the genes responsible for the production of the toxins ST-I, ST-II and Stx2, and the F4 gene with those of the enterotoxins ST-I, ST-II and LT. Both virulence patterns were detected more pronounced in E. coli strains with haemolytic activity. Fifty-six of a total of 83 E. coli isolates originating from calves were O-typed as O101 (O101:K28, O101:K30, O101:K32; n = 29), O78:K80 (n = 23), and O9:K35 (n = 4). Most of the E. coli O78:K80 strains carried the F17 gene (69.6%, n = 16). Virulence genes encoding for F4, F5 or ST-I were detected only in single cases. Intimin and Shiga toxin genes that are present in enterohaemorrhagic E. coli (EHEC) were not detected.  相似文献   

9.
Fimbriae and enterotoxins are major virulence factors associated with enterotoxigenic Escherichia coli (ETEC). In this study, 3 sets of multiplex polymerase chain reaction (mPCR) assays targeting fimbriae, enterotoxins, and other adherence factors were developed for detecting ETEC. A total number of 188 E. coli field isolates were examined, and percentages of E. coli strains carrying each virulence factors were as follows: F4 (7.45%), F5 (29.79%), F6 (6.38%), F18 (15.43%), F41 (3.72%), STa (10.11%), STb (20.74%), LT (9.57%), Stx2e (2.13%), EAST1 (42.02%), F1 (67.55%), AIDA-I (2.66%), and pAA (7.45%). Of the 188 E. coli field isolates examined, 25.53% were found to be pathogenic ETEC, having both fimbriae and enterotoxins. However, the ratio increased to 44.68% when the presence of other adhesins was considered as criteria for virulence. Among the adherence factors, F1 was found to be the most prevalent. AIDA-I and pAA were also found with similar ratio as compared with other virulence factors. In addition, virulence patterns carrying these alternate adhesive genes with enterotoxins were detected with significant ratio. Therefore, it is desirable that alternate adhesins be considered as markers for diagnosis of ETEC.  相似文献   

10.
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   

11.
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   

12.
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   

13.
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   

14.
Identification of Escherichia coli causing porcine postweaning diarrhoea (PWD) or edema disease (ED) requires knowledge regarding the prevalent pathotypes within a given region. This study was undertaken to determine the present distribution of serogroups, hemolytic activity and virulence factor gene profiles among porcine pathogenic E. coli isolates in Denmark and to compare detection of these characteristics as diagnostic approaches. Five hundred and sixty-three E. coli were serogrouped using E. coli O-antisera and investigated for hemolytic activity. Of these, 219 isolates were further characterized using a 5'-nuclease PCR assay detecting genes for adhesion factors, enterotoxins and verocytotoxin 2e (VT2e). Forty-two different serogroups were found. The most prevalent serogroup was O149 accounting for 49.9% of all isolates, followed by O138 (14.9%), O139 (6.9%), O141 (4.1%) and O8 (3.7%). Hemolytic activity was detected in 87.7% of all isolates. Virulence factor genes detected were F4 (44.7%), F18 (39.3%), intimin (1.4%), F6 (0.9%), STb (77.6%), EAST1 (65.8%), LT (61.6%), STa (26.5%) and VT2e (16.4%). Six pathotypes accounted for 65.7% of all isolates investigated. Using possession of virulence factor genes as reference, O-serogrouping employing a selection of antisera representing common pig pathogenic serogroups and detection of hemolysis were evaluated as epidemiological markers for pathogenicity. Both criteria were associated with pathogenicity (P<0.001, for both), however, both methods also resulted in false classifications regarding pathogenicity for 11.9 and 13.2% of isolates, respectively. Detection of adhesion factor genes F4, F18 and intimin is suggested as an operational alternative when diagnosing PWD and ED.  相似文献   

15.
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   

16.
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   

17.
《Veterinary microbiology》1997,54(2):133-144
Enterotoxigenic (ETEC) and enterotoxaemic (ETEEC) Escherichia (E.) coli that express F18 (F107) fimbriae colonize the small intestine and cause diarrhoea and/or oedema disease in weaned pigs. So far, two antigenic variants of F18 can be distinguished with a common antigenic factor designated ‘a’ and two specific factors called ‘b’ and ‘c’. In this study the existence of crosswise anti-colonization immunity between E. coli strains that express F18ab or F18ac fimbrial variants, respectively, was demonstrated. Weaned pigs of susceptible genotype with respect to susceptibility to adhesion of E. coli with fimbriae F18 were inoculated with E. coli strains 3064STM (O157:K-:H-:F18ab; resistant to streptomycin) and 8199RIF (O141ab:K-:H4:F18ac; resistant to rifampicin). The faecal shedding was compared subsequent to immunization and homologous or heterologous challenge. An enzyme-linked immunosorbent assay (ELISA) was applied to measure IgA, IgM and IgG antibodies against the F18ab and F18ac antigens in saliva, faeces, serum and intestinal wash samples. About 8 log CFU/g of the inoculated strains were found in faeces of all pigs following immunization as well as in non-immunized controls after challenge. Bacterial counts of the inoculated strains after challenge were between 2 and 5 log lower, without any difference between homologous and heterologous challenge. Intestinal colonization with fimbriated E. coli resulted in production of significantly increased levels of anti-fimbrial antibodies, especially IgA, in serum and intestinal wash samples. There were higher levels of homologous than of heterologous anti-fimbrial antibodies. Production of antibodies against F18a or against another common fimbrial antigen is probably responsible for crosswise anti-colonization immunity between E. coli strains with F18ab and F18ac fimbrial variants. Serum F18-specific IgA may be a useful indicator of a mucosal immune response directed against F18 fimbriae.  相似文献   

18.
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   

19.
本研究旨在建立一种快速鉴定致猪水肿病大肠埃希菌的多重PCR检测方法.分别针对大肠埃希菌16S rDNA、志贺毒素Stx2e A亚基和菌毛F18ab A亚基保守序列设计合成3对特异性引物,优化多重PCR反应条件,并进行特异性和敏感性检测.结果显示,阳性对照菌株扩增产物大小分别为1 062、733和313 bp.特异性和灵敏性检测结果表明,与肠炎沙门菌、多杀性巴氏杆菌、胸膜肺炎放线杆菌、副猪嗜血杆菌、支气管败血波氏杆菌和猪链球菌等猪常见致病菌均无交叉反应;菌体直接扩增法最低检出量为1 875 CFU.利用建立的多重PCR检测方法对分离收集的128株大肠埃希菌进行鉴定,得到36株致猪水肿病大肠埃希菌,其中30株既有菌毛F18ab又产志贺毒素Stx2e,另外6株仅产志贺毒素Stx2e.结果表明,本试验所建立的多重PCR检测方法对致猪水肿病大肠埃希菌的快速诊断和流行病学调查具有一定的应用价值.  相似文献   

20.
We tested hemolytic E. coli from 86 pigs with edema disease or colidiarrhea. They were tested serologically and with nonradioactive digoxigenin-dUTP labelled probes for the presence of enterotoxin or Shiga-like-toxin genes. By slide-agglutination we detected 38 cases with E. coli O149:K88, 28 with E. coli O139:82B and 20 with E. coli O141. E. coli of serogroup O149:K88 isolated from diarrheic pigs, reacted with the probes for LT and STb genes. Edema disease E. coli O139:82B reacted with the SLTII probe. E. coli O141, isolated from colidiarrhea or edema disease showed a diversity of toxin gene patterns. All the E. coli O141 from diarrheic pigs reacted with the probes for LT and STap in addition to SLTII. No strains isolated from pigs with edema disease possessed any of these enterotoxin genes. Gene probe technique confirmed the serological method as useful tool for diagnosing E. coli O149:K88 and O139:82B as ETEC or VTEC, respectively. On the other hand only the demonstration of toxin genes with probes could explain the pathological findings in the pigs shedding E. coli of serogroup O141.  相似文献   

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