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1.
The uropathogenic Escherichia coli wild-type strain 536 produces S-fimbriae, P-related fimbriae and type I fimbriae. Using immuno-colony dot and ELISA techniques, variants were detected showing an increased degree of S-fimbrial production. It was demonstrated by immunofluorescence microscopy that in normal (wild-type) and hyper-S-fimbriated E. coli populations non-fimbriated cells also exist, and that the percentage of S-fimbriated and non-fimbriated bacteria was roughly identical in either population. Hyper-S-fimbriated variants could be stably maintained. The transition from wild-type to hyper-S-fimbriation, which occurs spontaneously, is markedly higher than vice versa. Southern blot analysis of the S fimbrial adhesin (sfa) determinants of normal and hyper-fimbriated strains revealed no marked difference in the gene structure. 相似文献
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Enteroaggregative Escherichia coli (EAEC) is distinguished by its characteristic aggregative adherence (AA) pattern to cultured epithelial cells. In this study we investigated the role of type I fimbriae (TIF) in the AA pattern to HEp-2 cells and in biofilm formation. Accentuation of this pattern was observed when the adherence assay was performed in the absence of mannose. This effect was observed in the prototype EAEC strain 042 (O44:H18), O128:H35 strains and for other EAEC serotypes. Antiserum against TIF decreased AA by 70% and 90% for strains 042 and 18 (O128:H35 prototype strain), respectively. A non-polar knockout of fimD, the TIF usher, in strains 042 and 18 resulted in inhibition of the accentuated AA pattern of approximately 80% and 70% respectively, and biofilm formation diminution of 49% for 042::fimD and 76% for 18::fimD. Our data evidence a role for TIF in the AA pattern and in EAEC biofilm formation, demonstrating that these phenotypes are multifactorial. 相似文献
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The F165(1) fimbrial system has been associated with the resistance of Escherichia coli O115:K"V165" to phagocytic killing by porcine polymorphonuclear leukocytes (PMNLs). One mechanism of this resistance seemed to be inhibition of the oxidative response as observed following induction of PMNLs by phorbol myristate acetate (PMA) and treatment with bacteria possessing the F165(1) fimbriae. In order to confirm whether or not the F165(1) fimbriae are involved in this inhibition, we evaluated the effect of F165(1)-positive strains (a pathogenic wild-type strain 5131, and a recombinant strain HB101(pCJ7)) or an F165(1)-negative strain HB101 (used as negative control) on the oxidative response of porcine neutrophils (pNs) stimulated with PMA. Incubation of pNs with pathogenic E. coli strain 5131 resulted in significant inhibition of the oxidative response as compared to that observed for pNs incubated without bacteria, as assessed by hydrogen peroxide (H2O2) and superoxide anion (O2-) release from the phagocytes, and by the chemiluminescence assay. Similarly, incubation of pNs with the F165(1)-producing cloned strain HB101(pCJ7) resulted in significant inhibition of the pN oxidative response as compared to that observed for pNs incubated without bacteria or with strain HB101. In contrast, addition of purified F165(1) fimbriae to the pNs had no effect on the oxidative response. 相似文献
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Whereas several important virulence factors in Escherichia coli O157 have been identified, studies suggest they are not always essential and are probably insufficient to account for the severe clinical manifestation of E. coli O157 infection. Identification of putative virulence determinants is crucial to the understanding of bacterial pathogenesis and genomic comparison analysis may aid the characterisation of unidentified virulence attributes. In this study, representational difference analysis (RDA) was used for genomic comparison of E. coli O157 with the proposed ancestral strain, E. coli O55. Unique E. coli O157 gene sequences were isolated and one, termed RDA-1, taken forward for further analysis. Southern blotting with labelled RDA-1 as a probe showed it to be present in 77% of E. coli O157 isolates and absent in all non-E. coli O157 screened. Sequence flanking RDA-1 was obtained from a genomic clone identified by hybridisation, and contained an open reading frame predicted to encode a novel iron-regulated outer membrane protein. 相似文献
5.
Jorge Blanco Miguel Blanco María Pilar Alonso Jesús E. Blanco JoséIgnacio Garabal Enrique A. González 《FEMS microbiology letters》1992,96(2-3):155-159
The serogroups of 396 necrotizing Escherichia coli of human and bovine origin isolated in Spain between 1979 and 1991 have been determined. The 270 cytotoxic necrotizing factor strains belonged to 22 different O serogroups; however, 84% (226 of 270) were of one of seven serogroups (O2, O4, O6, O14, O22, O75 and O83). Although necrotizing E. coli producing cytotoxic necrotizing factor 2 belonged to 28 different serogroups, only six of them (O1, O3, O15, O55, O88 and O123) accounted for 60% (76 of 126) of cytotoxic necrotizing factor 2 strains. Furthermore, only 3% (4 of 126) of cytotoxic necrotizing factor 2 strains belonged to serogroups most common among strains producing cytotoxic necrotizing factor 1. The majority of necrotizing E. coli producing cytotoxic necrotizing factor 1 were obtained from human extraintestinal infections, whereas cytotoxic necrotizing factor 2 strains were isolated from stools of healthy and diarrhoeic calves. 相似文献
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分析腹泻仔猪大肠埃希菌(
本课题组前期研究从腹泻仔猪粪便样本中分离到64株
腹泻仔猪
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The presence of the genes for Escherichia coli adherence factor (EAF), attaching and effacing lesion (eae) and bundle-forming pili (bfp) in 72 strains identified as enteropathogenic E. coli (EPEC) by slide agglutination was evaluated using hybridization and PCR. The adherence property of these strains was assayed using 3h HeLa cells adherence assay. The results obtained indicated that virulence-associated genes were present in 65% of the strains but only ten (13.9%) isolates were positive for all the three markers (typical EPEC), 37 (51.4%) isolates carried either one or two of these determinants (atypical EPEC) and the remaining 25 (34.7%) were negative for all these genes. In vitro adherence assay showed that 44 (61.1%) strains adhered to HeLa cells with a defined pattern, 13 (18.1%) isolates adhered loosely with no definite pattern and the remaining 15 (20.8%) were non-adherent. Analysis of the results showed a statistically significant association between the presence of the virulence-related genes with adherence of the strains with a defined pattern (P=0.0001). These results indicated that since over 60% of the strains identified by serogrouping carried at least one of the putative virulence markers, it therefore seems that this simple test is still of value in our setting although the need for a confirmatory test is also indicated. 相似文献
9.
O'Hanlon KA Catarame TM Duffy G Blair IS McDowell DA 《Journal of applied microbiology》2004,96(5):1013-1023
AIM: To develop a real-time PCR detection procedure for Escherichia coli O111, O26 and O157 from minced meat. METHODS AND RESULTS: Strains (n = 8) of each of E. coli O26, E. coli O111 and E. coli O157 were inoculated at ca 10-20 CFU g(-1) into minced retail meat and enriched for 6 h at 41.5 degrees C as follows: E. coli O26 in tryptone soya broth (TSB) supplemented with cefixime (50 microg l(-1)), vancomycin (40 mg l(-1)) and potassium tellurite (2.5 mg l(-1)); E. coli O111 in TSB supplemented with cefixime (50 microg l(-1)) and vancomycin (40 mg l(-1)); E. coli O157 in E. coli broth supplemented with novobiocin (20 mg l(-1)). DNA was extracted from the enriched cultures, and detected and quantified by real-time PCR using verotoxin (vt1 and vt2) and serogroup (O157 per gene; O26 fliC-fliA genes and O111 wzy gene) specific primers. CONCLUSIONS: The methods outlined were found to be sensitive and specific for the routine detection of E. coli O111, O26 and O157 in minced beef. SIGNIFICANCE AND IMPACT OF THE STUDY: The enrichment, isolation and detection procedures used in this study provide a rapid routine-based molecular method for the detection and differentiation of E. coli O26, O111 and O157 from minced meat. 相似文献
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AIMS: To test the efficacy of Lactobacillus johnsonii FI9785 in reducing the colonization and shedding of Salmonella enterica serotype Enteritidis, Escherichia coli O78:K80 and Clostridium perfringens in poultry. METHODS AND RESULTS: Specific pathogen-free chicks (1 day old) were dosed with a single oral inoculum of 1x10(9) CFU. Lactobacillus johnsonii FI9785 and 24 h later were challenged in separate experiments with S. Enteritidis (S1400, nalr) and E. coli O78:K80 (EC34195, nalr). There were no significant effects against S. Enteritidis whereas colonization of the small intestine by E. coli O78:K80 was reduced significantly. Both S. Enteritidis and E. coli colonized the caeca and colon to levels equivalent to control birds and there was no reduction in shedding as assessed by a semi-quantitative cloacal swabbing technique. Specific pathogen-free chicks (20 day old) were dosed with a single oral inoculum of 1x10(9) CFU L. johnsonii FI9785 and 24 h later were challenged with C. perfringens. A single oral dose of L. johnsonii FI9785 was sufficient to suppress all aspects of colonization and persistence of C. perfringens. CONCLUSIONS: Lactobacillus johnsonii FI9785 may be given to poultry for use as a competitive exclusion agent to control C. perfringens. SIGNIFICANCE AND IMPACT OF THE STUDY: Lactobacillus johnsonii FI9785 may be a valuable tool to control the endemic disease of necrotic enteritis, thereby reducing economic losses associated with reduced use of antimicrobials in the poultry industry. 相似文献
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Uptake of d-glucose, l-lysine and l-proline and the kinetic parameters of alkaline phosphatase and γ-glutamyl-transpeptidase were evaluated in renal brush border membrane (BBM) vesicles prepared from control, pyelonephritic and iron-administered pyelonephritic rats. The uptake of d-glucose and amino acids and Vmax of both the enzymes studied were found to be altered in pyelonephritic and iron-administered pyelonephritic rats, but changes appeared earlier and more severely in iron-administered infected animals than in other infected animals. These early physiological alterations were accompanied by higher bacterial colonisation in iron-administered rats. 相似文献
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Identification of novel virulence-associated loci in uropathogenic Escherichia coli by suppression subtractive hybridization 总被引:10,自引:0,他引:10
To identify novel virulence-associated genes in uropathogenic Escherichia coli (UPEC) strains, a suppression subtractive hybridization strategy was applied to genomic DNA of four clinical UPEC isolates from patients suffering from cystitis or pyelonephritis. The genomic DNA of four isolates (tester strains) was subtracted from the DNA of two different driver strains, the well characterized UPEC strain CFT073 and the non-pathogenic E. coli K-12 strain MG1655. We determined the sequence of 172 tester strain-specific DNA fragments, 86 of which revealed only low or no homology to nucleotide sequences of public databases. We further determined the virulence association of the 86 novel DNA fragments using each DNA fragment as a probe in Southern hybridizations of a reference strain collection consisting of 60 extraintestinal pathogenic E. coli isolates, and 40 non-virulent E. coli strains from stool samples. From this, 19 novel DNA fragments were demonstrated to be significantly associated with virulent strains and thus may represent new virulence traits. Our results support the idea of a considerable genetic variability among UPEC strains and suggest that novel genomic determinants might contribute to virulence of UPEC. 相似文献
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OmpT is a protease associated with the outer membrane of Escherichia coli and possesses a high degree of homology to the plasminogen activator, Pla, of Yersinia pestis. We show here that OmpT from intact cells can indeed activate plasminogen. Clinical specimens of E. coli were examined for protease activity and for the ompT gene. Few isolates (12%) were found to be positive for OmpT activity, whereas most (77%) carried the ompT gene and expressed the cloned protease gene. In this report we present evidence suggesting that the surface architecture of E. coli influences the activity of OmpT and that OmpT may be indicative of the pathogenic potential of the organism. 相似文献
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Quan Wang rei V. Perepelov Lu Feng Yuriy A. Knirel Yang Li & Lei Wang 《FEMS immunology and medical microbiology》2009,55(1):47-54
The O-antigen, consisting of many repeats of an oligosaccharide, is an essential component of the lipopolysaccharide on the surface of Gram-negative bacteria. The O-antigen is one of the most variable cell constituents, and different O-antigen forms are almost entirely due to genetic variations in O-antigen gene clusters. In this paper, we present structural and genetic evidence for a close relationship between Escherichia coli O107 and E. coli O117 O antigens. The O-antigen of E. coli O107 has a pentasaccharide repeating unit with the following structure: →4)-β- d -Gal p NAc-(1→3)-α- l -Rha p -(1→4)-α- d -Glc p NAc-(1→4)-β- d -Gal p -(1→3)-α- d -Gal p NAc-(1→, which differs from the known repeating unit of E. coli O117 only in the substitution of d -GlcNAc for d -Glc. The O-antigen gene clusters of E. coli O107 and O117 share 98.6% overall DNA identity and contain the same set of genes in the same organization. It is proposed that one cluster was evolved from another via mutations, and the substitution of a few amino acids residues in predicted glycosyltransferases resulted in the functional change of one such protein for transferring different sugars in O107 ( d -GlcNAc) and O117 ( d -Glc), leading to different O-antigen structures. This is an example of the O-antigen alteration caused by nucleotide mutations, which is less commonly reported for O-antigen variations. 相似文献
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B. Picard N. Picard-Pasquier R. Krishnamoorthy Ph. Goullet 《FEMS microbiology letters》1991,82(2):183-188
Patterns of ribosomal DNA polymorphism were examined to compare carboxylesterase B type B1 strains and B2 strains of Escherichia coli isolated from extra-intestinal infections. DNA from 14 type B2 strains showing the presence of alpha-haemolysin and mannose-resistant haemagglutinin and lethality to mice and 14 type B1 strains lacking these characteristics, was digested with HindIII, EcoRI, BamHI or BglII restriction enzymes and analysed by Southern blotting. The obtained ribotypes clearly differentiated the B2 strains from the B1 strains. These results indicate that genotypes of the highly virulent B2 strains are different from that of the less virulent B1 strains. 相似文献
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Jorge Blanco M. Pilar Alonso Miguel Blanco Jesús E. Blanco Enrique A. González J. Ignacio Garabal 《FEMS microbiology letters》1992,99(2-3):131-136
Eight hundred and nineteen strains of Escherichia coli isolated in Spain between 1986 and 1991 from extraintestinal infections and feces of healthy controls were investigated for expression of P-fimbriae using a particle agglutination test. Among strains causing urinary tract infections, sepsis and other extraintestinal infections, P-fimbriae were found in 31% (130/420) (P < 0.001), 25% (30/118) (P < 0.001) and 12% (11/92) (P < 0.5) respectively. In contrast, only 7% (14/189) of faecal isolates from healthy individuals carried P-fimbriae. According to two more common toxic markers detected in this study (alpha-haemolysin and cytotoxic necrotizing factor type 1), P-fimbriated E. coli strains were grouped into three categories: haemolysin+cytotoxic necrosing factor+ (Hly+CNF1+) (68/185; 37%), haemolysin+cytotoxic necrosing factor- (Hly+CNF1-) (61/185; 33%) and Hly-CNF1- (56/185; 30%). The 185 P-fimbriated strains belonged to 17 different O serogroups. However, 148 (80%) were of one of six serogroups (O1, O2, O4, O6, O7 and O18). The most frequent serogroups determined in the Hly+CNF1+ strains were the O4 and O6 (53/68; 78%), in the Hly+CNF1- strains it was the O18 (27/61; 44%) and in the Hly-CNF1- strains the O1, O2 and O7 (41/56; 73%). The majority (160/185; 86%) of P-fimbriated E. coli expressed the mannose-resistant haemagglutinin type IVa. 相似文献
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Abstract Escherichia coli F-18, a normal human fecal isolate, is an excellent colonizer of the streptomycin-treated mouse large intestine. E. coli F-18Col− , a derivative of E. coli F-18 which no longer makes the E. coli F-18 colicin, colonizes the large intestine as well as E. coli F-18 when fed to mice alone but is eliminated when fed together with E. coli F-18. Recently we randomly cloned E. coli F-18 DNA into E. coli F-18Col− and let the mouse intestine select the best colonizer. In this way, we isolated a 6.5-kb E. coli F-18 DNA sequence that simultaneously stimulated synthesis of type 1 fimbriae and enhanced E. coli F-18Col− colonizing ability. In the present investigation we show that the gene responsible for stimulation of type 1 fimbriae synthesis appears to be leuX , which encodes a tRNA specific for the rare leucine codon UUG. Moreover, it appears that expression of leuX may be regulated by two proteins (22 kDa and 26 kDa) encoded by genes immediately adjacent to leuX . 相似文献
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Shelton DR Karns JS Higgins JA Van Kessel JA Perdue ML Belt KT Russell-Anelli J Debroy C 《FEMS microbiology letters》2006,261(1):95-101
Enterohemorrhagic Escherichia coli (EHEC) are a physiologically, immunologically and genetically diverse collection of strains that pose a serious water-borne threat to human health. Consequently, immunological and PCR assays have been developed for the rapid, sensitive detection of presumptive EHEC. However, the ability of these assays to consistently detect presumptive EHEC while excluding closely related non-EHEC strains has not been documented. We conducted a 30-month monitoring study of a major metropolitan watershed. Surface water samples were analyzed using an immunological assay for E. coli O157 (the predominant strain worldwide) and a multiplex PCR assay for the virulence genes stx(1), stx(2) and eae. The mean frequency of water samples positive for the presence of E. coli O157, stx(1) or stx(2) genes, or the eae gene was 50%, 26% and 96%, respectively. Quantitative analysis of selected enriched water samples indicated that even in samples positive for E. coli O157 cells, stx(1)/stx(2) genes, and the eae gene, the concentrations were rarely comparable. Seventeen E. coli O157 strains were isolated, however, none were EHEC. These data indicate the presence of multiple strains similar to EHEC but less pathogenic. These findings have important ramifications for the rapid detection of presumptive EHEC; namely, that current immunological or PCR assays cannot reliably identify water-borne EHEC strains. 相似文献