Characterization of Escherichia coli strains isolated from environmental water habitats and from stool samples of healthy volunteers

Mühldorfer, Inge; Blum, Gabriele; Donohue‐Rolfe, Arthur; Heier, H.; Ölschläger, Tobias; Tschäpe, Helmut; Wallner, Ursula; Häcker, J.

doi:10.1016/0923-2508(96)84019-8

Cited by 34 publications

(34 citation statements)

References 41 publications

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“…This result might be considered somewhat unexpected since cancer patients are often severely immunocompromised and thus could have been infected by much less virulent strains. The frequencies of the papC, hlyC, cnf1, and iut genes in both fecal and blood isolates were similar to those reported previously (35,40). The high frequency of carriage of the cnf1 gene in our collection of E. coli blood isolates was also in agreement with a previous report on the phenotypic expression of CNF in these strains (6), suggesting that cnf1 plays a role in the pathogenicity of these isolates (16,20,27).…”

Section: Discussionsupporting

confidence: 80%

Prevalence of Virulence Genes and Clonality in Escherichia coli Strains That Cause Bacteremia in Cancer Patients

et al. 2000

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Phenotypic analysis of Escherichia coli strains causing bacteremia in cancer patients suggests that they possess specific virulence properties. To investigate this hypothesis, we compared the frequency of the virulence-related genes cnf1, cnf2, papC, hlyC, and iut in 155 E. coli strains isolated from hospitalized cancer patients with epidemiologically unrelated cases of bacteremia to their frequency in 70 E. coli strains isolated from the feces of healthy unrelated volunteers. Of the blood isolates, 24, 37, and 26% were positive for cnf1, papC, and hlyC, respectively, versus only 6, 17, and 6% of the fecal isolates (P < 0.05 in all instances). By contrast, 47% of both isolates carried the iut gene. The patients' clinical characteristics did not significantly influence these frequencies. The presence on various pathogenicity islands (PAIs) of a combination of the cnf1, papC, and hlyC genes on the chromosome was strongly suggested by Southern blotting of pulsed-field gel electrophoresis (PFGE) patterns with specific DNA probes. The phylogenetic relatedness among 60 strains carrying three, two, one, or no virulence genes and 6 ECOR strains included as references was determined by neighbor joining, the unweighted pair-group method with arithmetic mean, and Wagner analysis of the randomly amplified polymorphic DNA (RAPD) patterns generated by 11 primers. Identification of a major cluster including 96.4% of the strains carrying the cnf1, papC, and hlyC genes and ECOR subgroup B2 strains suggested that the virulent E. coli strains causing bacteremia in cancer patients are closely related to ECOR B2 strains. The presence in the E. coli population surveyed of a strong linkage disequilibrium, and especially of a highly significant correlation between PFGE and RAPD genetic distances, confirms that clonal propagation has a major impact on the E. coli population structure. Nevertheless, low bootstrap values in the phylogenetic tree suggested that frequent genetic exchange inhibits the individualization of discrete genetic lineages, which are stable on an evolutionary scale.Patients with cancer are highly susceptible to bacterial infections, particularly during the periods of severe neutropenia that follow anticancer chemotherapy. Bloodstream infections caused by gram-negative bacteria are among the most frequent of these infections and are associated with a high mortality rate (1). Most of the gram-negative bacteria that cause these bloodstream infections originate in the intestinal flora (55) and reach the blood by a mechanism called bacterial translocation (for a review, see reference 4). In experimental models, bacterial translocation is enhanced by intestinal colonization and overgrowth of the translocating bacteria, by immunosuppression of the host, and by alterations of the intestinal mucosa (for a review, see reference 4), all of which may occur in cancer patients.Escherichia coli is the most common gram-negative species isolated from cancer patients with bacteremia (1, 55). Phenotypic studies performed on a series of...

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Section: Discussionsupporting

confidence: 80%

Prevalence of Virulence Genes and Clonality in Escherichia coli Strains That Cause Bacteremia in Cancer Patients

et al. 2000

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“…The UPEC strain P42 and the fecal O18:K1 isolate F54 belong to the strain collection of the Department of Microbiology, Immunology and Glycobiology, Lund University, Lund, Sweden. The E. coli K-12 strain MG1655 and E. coli strain B, as well as the six commensal fecal isolates, have been described before (6,41,56). All of the strains were grown in Luria-Bertani medium (51).…”

Section: Methodsmentioning

confidence: 99%

Analysis of Genome Plasticity in Pathogenic and Commensal Escherichia coli Isolates by Use of DNA Arrays

et al. 2003

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Genomes of prokaryotes differ significantly in size and DNA composition. Escherichia coli is considered a model organism to analyze the processes involved in bacterial genome evolution, as the species comprises numerous pathogenic and commensal variants. Pathogenic and nonpathogenic E. coli strains differ in the presence and absence of additional DNA elements contributing to specific virulence traits and also in the presence and absence of additional genetic information. To analyze the genetic diversity of pathogenic and commensal E. coli isolates, a whole-genome approach was applied. Using DNA arrays, the presence of all translatable open reading frames (ORFs) of nonpathogenic E. coli K-12 strain MG1655 was investigated in 26 E. coli isolates, including various extraintestinal and intestinal pathogenic E. coli isolates, 3 pathogenicity island deletion mutants, and commensal and laboratory strains. Additionally, the presence of virulenceassociated genes of E. coli was determined using a DNA "pathoarray" developed in our laboratory. The frequency and distributional pattern of genomic variations vary widely in different E. coli strains. Up to 10% of the E. coli K-12-specific ORFs were not detectable in the genomes of the different strains. DNA sequences described for extraintestinal or intestinal pathogenic E. coli are more frequently detectable in isolates of the same origin than in other pathotypes. Several genes coding for virulence or fitness factors are also present in commensal E. coli isolates. Based on these results, the conserved E. coli core genome is estimated to consist of at least 3,100 translatable ORFs. The absence of K-12-specific ORFs was detectable in all chromosomal regions. These data demonstrate the great genome heterogeneity and genetic diversity among E. coli strains and underline the fact that both the acquisition and deletion of DNA elements are important processes involved in the evolution of prokaryotes.

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“…The genes encoding Shiga toxins (stx) are generally carried by lambdoid bacteriophages and can be induced by DNAdamaging agents such as mitomycin C (Muhldorfer et al, 1996). As a result of the induction process, expression of stx 2 genes, which is under the control of a late phage promoter (Wagner et al, 2001), is activated.…”

Section: Introductionmentioning

confidence: 99%

Differential expression of stx2 variants in Shiga toxin-producing Escherichia coli belonging to seropathotypes A and C

Sablet¹,

Bertin²,

Vareille³

et al. 2008

Microbiology

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Only a subset of Shiga toxin (Stx)-producing Escherichia coli (STEC) are human pathogens, but the characteristics that account for differences in pathogenicity are not well understood. In this study, we investigated the distribution of the stx variants coding for Stx2 and its variants in highly virulent STEC of seropathotype A and low-pathogenic STEC of seropathotype C. We analysed and compared transcription of the corresponding genes, production of Shiga toxins, and stx-phage release in basal as well as in induced conditions. We found that the stx 2 variant was mainly associated with strains of seropathotype A, whereas most of the strains of seropathotype C possessed the stx 2-vhb variant, which was frequently associated with stx 2 , stx 2-vha or stx 2c . Levels of stx 2 and stx 2 -related mRNA were higher in strains belonging to seropathotype A and in those strains of seropathotype C that express the stx 2 variant than in the remaining strains of seropathotype C. The stx 2-vhb genes were the least expressed, in basal as well as in induced conditions, and in many cases did not seem to be carried by an inducible prophage. A clear correlation was observed between stx mRNA levels and stx-phage DNA in the culture supernatants, suggesting that most stx 2 -related genes are expressed only when they are carried by a phage. In conclusion, some relationship between stx 2 -related gene expression in vitro and the seropathotype of the STEC strains was observed. A higher expression of the stx 2 gene and a higher release of its product, in basal as well as in induced conditions, was observed in pathogenic strains of seropathotype A. A subset of strains of seropathotype C shows the same characteristics and could be a high risk to human health.

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Characterization of Escherichia coli strains isolated from environmental water habitats and from stool samples of healthy volunteers

Cited by 34 publications

References 41 publications

Prevalence of Virulence Genes and Clonality in Escherichia coli Strains That Cause Bacteremia in Cancer Patients

Prevalence of Virulence Genes and Clonality in Escherichia coli Strains That Cause Bacteremia in Cancer Patients

Analysis of Genome Plasticity in Pathogenic and Commensal Escherichia coli Isolates by Use of DNA Arrays

Differential expression of stx2 variants in Shiga toxin-producing Escherichia coli belonging to seropathotypes A and C

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