DNA sequence analysis of the composite plasmid pTC conferring virulence and antimicrobial resistance for porcine enterotoxigenic Escherichia coli.

In this study the plasmid pTC, a 90 kb self-conjugative virulence plasmid of the porcine enterotoxigenic Escherichia coli (ETEC) strain EC2173 encoding the STa and STb heat-stable enterotoxins and tetracycline resistance, has been sequenced in two steps. As a result we identified five main distinct regions of pTC: (i) the maintenance region responsible for the extreme stability of the plasmid, (ii) the TSL (toxin-specific locus comprising the estA and estB genes) which is unique and characteristic for pTC, (iii) a Tn10 transposon, encoding tetracycline resistance, (iv) the tra (plasmid transfer) region, and (v) the colE1-like origin of replication. It is concluded that pTC is a self-transmissible composite plasmid harbouring antibiotic resistance and virulence genes.

Pathogenomics: an updated European Research Agenda.

The emerging genomic technologies and bioinformatics provide novel opportunities for studying life-threatening human pathogens and to develop new applications for the improvement of human and animal health and the prevention, treatment, and diagnosis of infections. Based on the ecology and population biology of pathogens and related organisms and their connection to epidemiology, more accurate typing technologies and approaches will lead to better means of disease control. The analysis of the genome plasticity and gene pools of pathogenic bacteria including antigenic diversity and antigenic variation results in more effective vaccines and vaccine implementation programs.

Both alpha-haemolysin determinants contribute to full virulence of uropathogenic Escherichia coli strain 536.

Uropathogenic Escherichia coli strain 536 possesses two intact copies of the alpha-haemolysin determinant localised on distinct pathogenicity islands. The coding regions of the two hlyCABD operons are conserved; however, upstream sequences are entirely dissimilar. Consequently, expression of the encoded toxin molecules in vitro is highly different.

Characterization of an F18+ enterotoxigenic Escherichia coli strain from post weaning diarrhoea of swine, and of its conjugative virulence plasmid pTC.

The enterotoxigenic Escherichia coli (ETEC) strain Ec2173, causing post weaning diarrhoea in swine, harbours six plasmids ranging from 13 to 200 kb in size. The heat stable toxin genes sta, stb and a tetracycline resistance gene were located on a self conjugative 120-kb plasmid, called pTC. In the cloned ColE1 type origin of replication of pTC a deletion was detected compared to other ColE1 replicons affecting the replication modulator gene rom.

The pathogenicity island-associated K15 capsule determinant exhibits a novel genetic structure and correlates with virulence in uropathogenic Escherichia coli strain 536.

The K15 capsule determinant of uropathogenic Escherichia coli strain 536 (O6:K15:H31) is part of a novel 79.6-kb pathogenicity island (PAI) designated PAI V536 that is absent from the genome of nonpathogenic E. coli K-12 strain MG1655.

Instability of pathogenicity islands in uropathogenic Escherichia coli 536.

The uropathogenic Escherichia coli strain 536 carries at least five genetic elements on its chromosome that meet all criteria characteristic of pathogenicity islands (PAIs). One main feature of these distinct DNA regions is their instability. We applied the so-called island-probing approach and individually labeled all five PAIs of E.

The molecular basis of infectious diseases: pathogenicity islands and other mobile genetic elements. A review.

Bacterial genomes generally consist of stable regions termed core genome, and variable regions that form the so-called flexible gene pool. The flexible part is composed of bacteriophages, plasmids, transposons as well as unstable large regions that have been termed genomic islands. Genomic islands encoding virulence factors of pathogenic bacteria have been designated "pathogenicity islands".

Detection of a plasmid-encoded pathogenicity island in F18+ enterotoxigenic and verotoxigenic Escherichia coli from weaned pigs.

Most virulence genes of enterotoxigenic Escherichia coli (ETEC) are located on plasmids. The gene for heat-stable enterotoxin I (sta) is part of the transposon Tn1681, and the heat-stable enterotoxin II (stb) gene was described to be part of the transposon Tn4521. In the studies presented here, we describe the linkage of the sta and stb genes on an approximately 10-kb fragment designated as toxin-specific locus (TSL).

Characterization of Escherichia coli strains causing urinary tract infections in patients with transposed intestinal segments.

Purpose: Transposition of intestinal segments into the urinary tract predisposes to urinary tract infections. We characterized bacterial infections in these patients and examined the virulence genotype and persistence of Escherichia coli isolates.

Materials And Methods: We followed 26 patients who underwent bladder reconstructive surgery using transposed intestinal segments.

Development of strain-specific PCR reactions for the detection of the probiotic Escherichia coli strain Nissle 1917 in fecal samples.

PCR was used to establish a specific detection system for the non-pathogenic Escherichia coli strain Nissle 1917 (DSM6601), which is used as a probiotic drug against intestinal disorders and diseases. Five PCR assays have been developed which are based on the chromosomally encoded major fimbrial subunit genes fimA (type 1 fimbriae) and focA (F1C fimbriae), and the two small cryptic plasmids pMUT1 and pMUT2. The assays were validated by testing a collection of 354 different pathogenic and non-pathogenic E.

Genetic structure and distribution of four pathogenicity islands (PAI I(536) to PAI IV(536)) of uropathogenic Escherichia coli strain 536.

For the uropathogenic Escherichia coli strain 536 (O6:K15:H31), the DNA sequences of three pathogenicity islands (PAIs) (PAI I(536) to PAI III(536)) and their flanking regions (about 270 kb) were determined to further characterize the virulence potential of this strain. PAI I(536) to PAI III(536) exhibit features typical of PAIs, such as (i) association with tRNA-encoding genes; (ii) G+C content differing from that of the host genome; (iii) flanking repeat structures; (iv) a mosaic-like structure comprising a multitude of functional, truncated, and nonfunctional putative open reading frames (ORFs) with known or unknown functions; and (v) the presence of many fragments of mobile genetic elements. PAI I(536) to PAI III(536) range between 68 and 102 kb in size.

A single nucleotide exchange in the wzy gene is responsible for the semirough O6 lipopolysaccharide phenotype and serum sensitivity of Escherichia coli strain Nissle 1917.

Structural analysis of lipopolysaccharide (LPS) isolated from semirough, serum-sensitive Escherichia coli strain Nissle 1917 (DSM 6601, serotype O6:K5:H1) revealed that this strain's LPS contains a bisphosphorylated hexaacyl lipid A and a tetradecasaccharide consisting of one E. coli O6 antigen repeating unit attached to the R1-type core. Configuration of the GlcNAc glycosidic linkage between O-antigen oligosaccharide and core (beta) differs from that interlinking the repeating units in the E.

S-Fimbria-encoding determinant sfa(I) is located on pathogenicity island III(536) of uropathogenic Escherichia coli strain 536.

The sfa(I) determinant encoding the S-fimbrial adhesin of uropathogenic Escherichia coli strains was found to be located on a pathogenicity island of uropathogenic E. coli strain 536. This pathogenicity island, designated PAI III(536), is located at 5.

A subtractive hybridisation analysis of genomic differences between the uropathogenic E. coli strain 536 and the E. coli K-12 strain MG1655.

Suppression subtractive hybridisation (SSH) was performed to identify genomic differences between the uropathogenic Escherichia coli strain 536 and the non-pathogenic E. coli K-12 strain MG1655. In total, 22 DNA fragments were isolated which were specific for strain 536.

Toxin genes on pathogenicity islands: impact for microbial evolution.

Toxin-specific genes are often located on mobile genetic elements such as phages, plasmids and pathogenicity islands (PAIs). The uropathogenic E. coli strain 536 carries two alpha-hemolysin gene clusters, which are part of the pathogenicity islands I536 and II536, respectively.

Evolution of microbial pathogens.

Various genetic mechanisms including point mutations, genetic rearrangements and lateral gene transfer processes contribute to the evolution of microbes. Long-term processes leading to the development of new species or subspecies are termed macroevolution, and short-term developments, which occur during days or weeks, are considered as microevolution. Both processes, macro- and microevolution need horizontal gene transfer, which is particularly important for the development of pathogenic microorganisms.

Virulence patterns from septicemic Escherichia coli O78 strains.

Several septicemic Escherichia coli O78 strains, isolated from different sources, were characterized phenotypically and genotypically. Two avian isolates, one of which is known to carry the AC/I fimbriae, hybridized with the sfa determinant in colony dot-blot assay. Southern hybridizations with specific sfa probes, following pulsed-field gel electrophoresis (PFGE), showed positive hybridization to the same fragment in each of these strains.

Pathogenicity islands of virulent bacteria: structure, function and impact on microbial evolution.

Virulence genes of pathogenic bacteria, which code for toxins, adhesins, invasins or other virulence factors, may be located on transmissible genetic elements such as transposons, plasmids or bacteriophages. In addition, such genes may be part of particular regions on the bacterial chromosomes, termed 'pathogenicity islands' (Pais). Pathogenicity islands are found in Gram-negative as well as in Gram-positive bacteria.

Characterization of Escherichia coli serotype O12:K1:H7 isolates from an immunocompetent carrier with a history of spontaneous abortion and septicemia.

Escherichia coli isolates from an immunocompetent woman with a history of repeated amnion infections and spontaneous abortion were characterized. Escherichia coli were isolated from stool, blood and cervix swab samples taken over a 21-month period after the last abortion which followed septicemia during pregnancy. All samples except the last cervix swab contained isolates of serotype O12:K1:H7, which produced adhesins, P fimbriae, type I fimbriae and the iron-chelator aerobactin.