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Herbert Schmidt

Publications and source records attributed to Herbert Schmidt.

At least 19 recordsLinked to original sources
PubMed2006

Complete sequence of the large virulence plasmid pSFO157 of the sorbitol-fermenting enterohemorrhagic Escherichia coli O157:H- strain 3072/96.

The large virulence plasmid pSFO157 of sorbitol-fermenting E. coli O157:H(-) strain 3072/96 has a size of 121,239bp and contains 96 open reading frames >50bp. It is therefore 29,162bp larger (ca. 32%) than plasmid pO157 of E. coli O157:H7 strain EDL933. Major differences between the plasmids are the absence of katP, espP, and toxB in pSFO157 and, instead of these, the presence of the sfp fimbriae gene cluster and a large part of an F-plasmid transfer region, the latter accounting for most of the additional DNA. The differences in the order of the genes and their composition, as well as the presence of a number of replication-associated genes and mobile genetic elements suggests that the large E. coli O157 virulence plasmids have a complex evolutionary origin.

Bacterial Proteins↗
PubMed2005

Serotypes and intimin types of intestinal and faecal strains of eae+ Escherichia coli from weaned pigs.

Enteropathogenic Escherichia coli (EPEC) that are known to cause severe diarrhoea in children and young rabbits are well characterized, but there are few reports on the serotypes and intimin (eae) types of EPEC in weaned pigs. Based on detection of the eae gene by PCR and by DNA-hybridisation with LEE specific gene probes, 20 intestinal and 17 faecal eae(+) strains from diarrhoeal (164) and non-diarrhoeal (57) weaned pigs from 13 Hungarian farms, representing 12.8% of diarrhoeal and 14.0% of non-diarrhoeal pigs, were identified. The dominant serotype was O123:H11 (40%) among intestinal, and O108:H9 (23%) among faecal strains. The majority (85%) of the intestinal strains possessed eae-beta and 10% carried eae-gamma gene. In contrast, significantly (p<0.025) fewer faecal strains (53%) harboured the eae-beta gene, and 23% were eae-gamma positive. In vitro adhesion tests of intestinal and faecal eae(+) strains indicated adhesion of 20/37 of the strains to PK15 (porcine kidney) cells while only 3/37 strains adhered to HeLa cells. The ultrastructure of intimate bacterial attachment of representative porcine eae(+) strains to PK15 cells showed no pedestal formation, in contrast to the human EPEC (O127:H5, eae-alpha) strain. In conclusion, the data do not demonstrate a significant role for the eae(+)E. coli in porcine post-weaning diarrhoea, but provide new information on a dominant porcine serotype (O123:H11, eae-beta), and on differences of serotypes and intimin types of porcine eae(+) strains according to their site of isolation. Furthermore there was an indication that the PK15 cell line could be used as a model to study in vitro adherence of eae(+)E. coli of some human and porcine origin.

Adhesins, Bacterial↗
PubMed2005

Characterization of two major groups of diarrheagenic Escherichia coli O26 strains which are globally spread in human patients and domestic animals of different species.

Twenty-three Escherichia coli O26 strains from humans, cattle, sheep, pigs and chicken were investigated for virulence markers and for genetic similarity by pulsed field gel electrophoresis and multi locus sequence typing. Two groups of genetically closely related O26 strains were defined. One group is formed by enteropathogenic (EPEC) and enterohemorrhagic (EHEC) E. coli strains, which do not ferment rhamnose and dulcitol and most of these carry a plasmid encoding enterohemolysin. The other group consists of rhamnose and dulcitol fermenting EPEC strains, which carry plasmids encoding alpha-hemolysin. Multiple species of domestic animals were shown to serve as a reservoir for human pathogenic O26 EPEC and EHEC strains.

Animals↗
PubMed2005

Genetic structure and chromosomal integration site of the cryptic prophage CP-1639 encoding Shiga toxin 1.

The sequence of 50 625 bp of chromosomal DNA derived from Shiga-toxin (Stx)-producing Escherichia coli (STEC) O111: H- strain 1639/77 was determined. This DNA fragment contains the cryptic Stx1-encoding prophage CP-1639 and its flanking chromosomal regions. The genome of CP-1639 basically resembles that of lambdoid phages in structure, but contains three IS629 elements, one of which disrupts the gene of a tail fibre component. The prophage genome lacks parts of the recombination region including integrase and excisionase genes. Moreover, a capsid protein gene is absent. CP-1639 is closely associated with an integrase gene of an ancient integrative element. This element consists of three ORFs of unknown origin and a truncated integrase gene homologous to intA of CP4-57. By PCR analysis and sequencing, it was shown that this integrative element is present in a number of non-O157 STEC serotypes and in non-STEC strains, where it is located at the 3'-end of the chromosomal ssrA gene. Whereas in most E. coli O111: H- strains, prophages are inserted in this site, E. coli O26 strains contain the integrative element not connected to a prophage. In E. coli O103 strains, the genetic structure of this region is variable. Comparison of DNA sequences of this particular site in E. coli O157: H7 strain EDL933, E. coli O111: H- strain 1639/77 and E. coli K-12 strain MG1655 showed that the ssrA gene is associated in all cases with the presence of foreign DNA. The results of this study have shown that the cryptic prophage CP-1639 is associated with an integrative element at a particular site in the E. coli chromosome that possesses high genetic variability.

Chromosome Mapping↗
PubMed2005

Global expression of prophage genes in Escherichia coli O157:H7 strain EDL933 in response to norfloxacin.

We investigated the influence of a low concentration of the gyrase inhibitor norfloxacin on the transcriptome of enterohemorrhagic Escherichia coli O157:H7 strain EDL933. For this purpose, we used a commercial DNA microarray containing oligonucleotides specific for E. coli O157:H7 strains EDL933 and RIMD0509952 and E. coli K-12 strain MG1655. Under the conditions applied, 5,963 spots (94% of all spots) could be analyzed. Among these, 118 spots (P < 0.05) indicated transcriptional upregulation and 122 spots (P < 0.05) indicated transcriptional downregulation of the E. coli genes present on the array. Eighty-five upregulated EDL933 genes were phage borne. Fifty-two of them could be ascribed to the Shiga toxin-encoding phages (Stx phages) BP-933W and CP-933V; the other 33 genes belonged to non-Stx prophage elements in the EDL933 genome. Genes present in the BP-933W prophage genome were induced most strongly up to 158-fold in the case of stxA(2) upon induction with norfloxacin. Twenty-two additional upregulated genes appeared to be E. coli O157:H7 strain RIMD0509952-specific phage elements, and the remaining 11 genes were related mainly to recombination and stress functions. Downregulation was indicated predominantly for genes responsible for bacterial primary metabolism, such as energy production, cell division, and amino acid biosynthesis. Interestingly, some genes present in the locus of enterocyte effacement appeared to be downregulated. The results of the study have shown that a low concentration of norfloxacin has profound effects on the transcriptome of E. coli O157:H7.

Anti-Infective Agents↗
PubMed2005

The Shiga toxin 1-converting bacteriophage BP-4795 encodes an NleA-like type III effector protein.

In this study, the complete DNA sequence of Shiga toxin 1-converting bacteriophage BP-4795 was determined. The genome of BP-4795 consists of 85 open reading frames, including two complete IS629 elements and three morons at the end of its late regulatory region. One of these morons encodes a type III effector that is translocated by the locus of enterocyte effacement-encoded type III secretion system into HeLa cells, where it localizes with the Golgi apparatus.

Base Sequence↗
PubMed2005

Genetic analysis of enteropathogenic and enterohemorrhagic Escherichia coli serogroup O103 strains by molecular typing of virulence and housekeeping genes and pulsed-field gel electrophoresis.

We investigated the genetic relationships of 54 Escherichia coli O103 strains from humans, animals, and meat by molecular typing of housekeeping and virulence genes and by pulsed-field gel electrophoresis (PFGE). Multilocus sequence typing (MLST) of seven housekeeping genes revealed seven profiles, I through VII. MLST profiles I plus III cover 45 Shiga toxin-producing E. coli (STEC) O103:H2 strains from Australia, Canada, France, Germany, and Northern Ireland that are characterized by the intimin (eae) epsilon gene and carry enterohemorrhagic E. coli (EHEC) virulence plasmids. MLST profile II groups five human and animal enteropathogenic E. coli (EPEC) O103:H2 strains that were positive for intimin (eae) beta. Although strains belonging to MLST groups II and I plus III are closely related to each other (92.6% identity), major differences were found in the housekeeping icdA gene and in the virulence-associated genes eae and escD. E. coli O103 strains with MLST patterns IV to VII are genetically distant from MLST I, II, and III strains, as are the non-O103 E. coli strains EDL933 (O157), MG1655 (K-12), and CFT073 (O6). Comparison of MLST results with those of PFGE and virulence typing demonstrated that E. coli O103 STEC and EPEC have recently acquired different virulence genes and DNA rearrangements, causing alterations in their PFGE patterns. PFGE typing was very useful for identification of genetically closely related subgroups among MLST I strains, such as Stx2-producing STEC O103 strains from patients with hemolytic uremic syndrome. Analysis of virulence genes contributed to grouping of E. coli O103 strains into EPEC and STEC. Novel virulence markers, such as efa (EHEC factor for adherence), paa (porcine adherence factor), and cif (cell cycle-inhibiting factor), were found widely associated with E. coli O103 EPEC and STEC strains.

Adhesins, Bacterial↗
PubMed2004

Endemic occurrence of infections by multidrug-resistant Escherichia coli of four unique serotypes in the elderly population of Israel.

During a period of four years, multidrug-resistant Escherichia coli of particular serotypes have been isolated from 255 elderly (>65 years) patients from four hospitals in central Israel. 83% of the isolates belonged to one of four predominant serotypes (O153:H31, O101:H-, O2:H42, and O102:H6). All isolates were producers of extended spectrum beta-lactamases and resistant to ciprofloxacin. To our knowledge, the involved serotypes have hitherto not been reported as etiological agents of extraintestinal human infections (MEDLINE). Pulsed-field gel electrophoresis of isolates from one of the most frequent serotypes indicated a clonal relationship between them. Further investigation of these strains and analysis of their virulence factors may help to confine their spread.

Aged↗
PubMed2004

Shiga toxin-encoding bacteriophages--genomes in motion.

Shiga toxins (Stx) represent a group of bacterial toxins that are involved in human and animal disease. Stx are mainly produced by Escherichia coli isolated from human and non-human sources, Shigella dysenteriae type 1, and sporadically, by Citrobacter freundii, Enterobacter cloacae and Shigella flexneri. The genes encoding Stx are encoded in the genome of heterogeneous lambdoid prophages (Stx-converting bacteriophages; Stx-phages). They are located in a similar position in the late region of the prophage genome and stx is under control of phage genes. Therefore, induction of Stx-converting prophages triggers increased production of Stx. Following induction, Stx-phages can infect other bacteria in vivo and in vitro. Stx-phages may be considered to represent highly mobile genetic elements that play an important role in the expression of Stx, in horizontal gene transfer, and hence in genome diversification.

Animals↗
PubMed2004

Pathogenicity islands in bacterial pathogenesis.

In this review, we focus on a group of mobile genetic elements designated pathogenicity islands (PAI). These elements play a pivotal role in the virulence of bacterial pathogens of humans and are also essential for virulence in pathogens of animals and plants. Characteristic molecular features of PAI of important human pathogens and their role in pathogenesis are described. The availability of a large number of genome sequences of pathogenic bacteria and their benign relatives currently offers a unique opportunity for the identification of novel pathogen-specific genomic islands. However, this knowledge has to be complemented by improved model systems for the analysis of virulence functions of bacterial pathogens. PAI apparently have been acquired during the speciation of pathogens from their nonpathogenic or environmental ancestors. The acquisition of PAI not only is an ancient evolutionary event that led to the appearance of bacterial pathogens on a timescale of millions of years but also may represent a mechanism that contributes to the appearance of new pathogens within a human life span. The acquisition of knowledge about PAI, their structure, their mobility, and the pathogenicity factors they encode not only is helpful in gaining a better understanding of bacterial evolution and interactions of pathogens with eukaryotic host cells but also may have important practical implications such as providing delivery systems for vaccination, tools for cell biology, and tools for the development of new strategies for therapy of bacterial infections.

Bacteria↗
PubMed2003

Multilocus sequence analysis of Porphyromonas gingivalis indicates frequent recombination.

In this study, the genetic relationship of 19 Porphyromonas gingivalis isolates from patients with periodontitis was investigated by multilocus sequence analysis. Internal 400-600 bp DNA fragments of the 10 chromosomal genes ef-tu, ftsQ, hagB, gpdxJ, pepO, mcmA, dnaK, recA, pga and nah were amplified by PCR and sequenced. No two isolates were identical at all 10 loci. Phylogenetic analyses indicated a panmictic population structure of P. gingivalis. Split decomposition analysis, calculation of homoplasy ratios and analyses of clustered polymorphisms all indicate that recombination plays a major role in creating the genetic heterogeneity of P. gingivalis. A standardized index of association of 0.0898 indicates that the P. gingivalis genes analysed are close to linkage equilibrium.

Chromosomes, Bacterial↗
PubMed2003

Transduction of porcine enteropathogenic Escherichia coli with a derivative of a shiga toxin 2-encoding bacteriophage in a porcine ligated ileal loop system.

In this study, we have investigated the ability of detoxified Shiga toxin (Stx)-converting bacteriophages Phi3538 (Deltastx(2)::cat) (H. Schmidt et al., Appl. Environ. Microbiol. 65:3855-3861, 1999) and H-19B::Tn10d-bla (D. W. Acheson et al., Infect. Immun. 66:4496-4498, 1998) to lysogenize enteropathogenic Escherichia coli (EPEC) strains in vivo. We were able to transduce the porcine EPEC strain 1390 (O45) with Phi3538 (Deltastx(2)::cat) in porcine ligated ileal loops but not the human EPEC prototype strain E2348/69 (O127). Neither strain 1390 nor strain E2348/69 was lysogenized under these in vivo conditions when E. coli K-12 containing H-19B::Tn10d-bla was used as the stx1 phage donor. The repeated success in the in vivo transduction of an Stx2-encoding phage to a porcine EPEC strain in pig loops was in contrast to failures in the in vitro trials with these and other EPEC strains. These results indicate that in vivo conditions are more effective for transduction of Stx2-encoding phages than in vitro conditions.

Animals↗
PubMed2003

HEp-2 cell adherence, actin aggregation, and intimin types of attaching and effacing Escherichia coli strains isolated from healthy infants in Germany and Australia.

Fecal samples from healthy children under 2 years of age living in Berlin, Germany (205 infants), and Melbourne, Australia (184 infants), were investigated for the presence of attaching and effacing (AE) Escherichia coli (AEEC) strains by screening for eae (intimin) genes. Twenty-seven AEEC strains were isolated from 14 children (7.6%) from Melbourne and from 12 children (5.9%) from Berlin. The 27 AEEC strains were classified as enterohemorrhagic E. coli (one strain, producing Shiga toxin 1), typical enteropathogenic E. coli (EPEC) (one strain carrying an EPEC adherence factor [EAF] plasmid), and atypical EPEC (25 strains negative for Shiga toxins and EAF plasmids). The AEEC were divided into 18 different serotypes, O-nontypeable and O-rough strains. Typing of their intimin genes revealed the presence of intimin alpha in 6 strains, intimin beta in 11 strains, intimin gamma in 7 strains, intimin zeta in 2 strains, and intimin eta in one strain. Analysis of HEp-2 cell adherence showed diffuse adherence or localized adherence-like patterns in 26 AEEC strains; local adherence was found only with the EAF-positive strain. Ten AEEC strains showed an AE property with the fluorescent actin staining (FAS) test. The introduction of an EAF plasmid (pMAR7) converted 11 FAS-negative AEEC strains to FAS positive and increased the FAS reaction in six FAS-positive AEEC strains, indicating that the genes needed for the AE phenotype were functional in these strains. Our finding indicates that atypical EPEC strains could play a double role as strains that naturally immunize against intimin in humans and as reservoirs for new emerging human pathogenic EPEC strains.

Actins↗
PubMed2003

Enteroaggregative Escherichia coli serotype O126:H27, Israel.

Enteroaggregative Escherichia coli (EAEC) is a newly diarrheagenic agent wherein several predominant serotypes are reported. We studied the association between those serotypes, as clonal indicators, and the trait of enteroaggregative adherence to host cells, tested by polymerase chain reaction. We also evaluated the clinical manifestations of infection in 17 hospitalized children by our most common EAEC serotype, O126:H27.

Communicable Diseases, Emerging↗
PubMed2002

Antibody reactivity of a standardized human serum protein solution against a spectrum of microbial pathogens and toxins: comparison with fresh frozen plasma.

In this study, we compared a standardized solution of human serum protein (HSP) and fresh frozen plasma (FFP) with regard to the antibody specificity against a number of microbial pathogens and some important pathogenicity factors of bacterial pathogens. Due to the clinical use of HSP and FFP for therapeutical plasma exchange, we have chosen a spectrum of microbial pathogens for serological analysis that is critical in clinical settings. With the enzyme-linked immunosorbent assay technique, we could show that HSP contains marked IgG antibody reactivity against antigens of Escherichia coli, Campylobacter jejuni, Enterobacter sakazakii, Proteus mirabilis, Pseudomonas aeruginosa, Klebsiella pneumoniae, Staphylococcus aureus, S. epidermidis, Streptococcus pneumoniae, Enterococcus faecalis, Chlamydia pneumoniae, and Candida albicans. Although no IgM antibodies against the pathogens tested could be detected in HSP, moderate IgA reactivity was found against 4 of 12 microbial antigens. Immunoblot analysis demonstrated specific IgA and IgG responses against the endoproteinase Glu-C and the superantigens enterotoxin A and B of S. aureus, the IgA-protease of Neisseria gonorrhoeae, and Shiga toxin 2 of enterohemorrhagic E. coli. By using 3 different HSP batches in parallel, we could demonstrate antibody reactivity against important microbial pathogens and toxins. This antibody profile is essentially more homogeneous than that of 3 batches of FFP.

Antibody Specificity↗
PubMed2002

The nucleotide sequence of Shiga toxin (Stx) 2e-encoding phage phiP27 is not related to other Stx phage genomes, but the modular genetic structure is conserved.

In this study we determined the complete nucleotide sequence of Shiga toxin 2e-encoding bacteriophage phi P27, isolated from the Shiga toxin-producing Escherichia coli patient isolate 2771/97. phi P27 is integrated as a prophage in the chromosomal yecE gene. This integration generates identity segments of attL and attR sites with lengths of 11 nucleotides. The integrated prophage genome has a size of 42,575 bp. We identified 58 open reading frames (ORFs), each with a length of >150 nucleotides. The deduced proteins of 44 ORFs showed significant homologies to other proteins present in sequence databases, whereas 14 putative proteins did not. For 29 proteins, we could deduce a putative function. Most of these are related to the basic phage propagation cycle. The phi P27 genome represents a mosaic composed of genetic elements which are obviously derived from related and unrelated phages. We identified five short linker sequences of 22 to 151 bp in the phi P27 sequence which have also been detected in a couple of other lambdoid phages. These linkers are located between functional modules in the phage genome and are thought to play a role in genetic recombination. Although the overall DNA sequence of phi P27 is not highly related to other known phages, the data obtained demonstrate a typical lambdoid genome structure.

Bacteriophages↗
PubMed2000

Identification and characterisation of Escherichia coli strains of O157 and non-O157 serogroups containing three distinct Shiga toxin genes.

Three Shiga toxin (Stx)-producing Escherichia coli (STEC) strains from patients with diarrhoea were identified, each of which contained three distinct stx genes (stx1, stx2 and stx2c). The strains belonged to the serotypes O52:H19, O75:H- and O157:H- and harboured eae and EHEC-hly sequences. Colony-blot immunoassay was used to demonstrate that both major types of Stx were expressed. The association of stx genes with either phage or phage DNA was demonstrated in all three strains. Isolated phage DNA from all strains contained stx1 sequences, but stx2 sequences were found only in phage DNA of two of these strains. The presence of three distinct stx genes may enhance the virulence of STEC strains and should be monitored. The observations demonstrate not only the potential of stx genes to spread within different serotypes, but also their capacity to accumulate within a single strain.

Animals↗