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Lothar H Wieler

Publications and source records attributed to Lothar H Wieler.

15 recordsLinked to original sources
PubMed2004

Molecular epidemiology of avian pathogenic Escherichia coli (APEC) isolated from colisepticemia in poultry.

The molecular biology and epidemiology of 150 avian pathogenic Escherichia coli strains (APEC) isolated from septicemic poultry in Germany was investigated by serotyping, pulsed field gel electrophoresis (PFGE), and polymerase chain reaction (PCR). Only 49.6% of the isolates could be grouped to serogroups O1, O2, and O78. Macrorestriction analyses data revealed two large clonal groups (clusters I and II) among the APEC strains with a similarity of 60.9% to each other. An association between restriction pattern and serogroup or origin of the strains was only present in a few subgroups of each clusters I and II, but was not evident. In contrast, our data revealed distinct combinations of virulence-associated genes in that 51.2% of the O2-strains harboured a combination of the genes fyuA, irp2, iucD, tsh, vat, fimC, and colV and 36.4% of the O78-strains possessed the same gene combination with exception of vat. With 34 different gene combinations the non-O1, -O2, -O78 isolates revealed a higher variability in their virulence gene pattern than O1-, O2-, and O78-strains with 6, 13, and 9 patterns, respectively. Our data indicate only a limited association between the virulence gene pattern and the serogroup of APEC strains and question the sensitivity of O-typing for APEC identification without the application of further diagnostic tools. Although a limited number of APEC clones exist, horizontal gene transfer seems to be common in these pathogens. These findings strengthen further research on the population structure of APEC and may be the reason for the lack of clear definition of this common E. coli pathotype.

Animals↗
PubMed2004

Molecular characteristics of Escherichia coli serogroup O78 strains isolated from diarrheal cases in bovines urge further investigations on their zoonotic potential.

We investigated the virulence properties and clonal relationship of 21 Escherichia coli strains of serogroup O78 isolated from diarrhoeic cattle and calves. Isolates were screened for 18 genes representing virulence features of different Escherichia coli pathotypes. None of the strains harboured enterotoxin-genes estIa/Ib, eltIa/Ib, or Shiga toxin (stx) genes, genes involved in adhesion (eae, f5, f41) hemolysin gene hlyA or invasion gene ipaC. With a high prevalence we detected enterotoxin astA (61.9%), genes involved in iron acquisition, like fyuA, irp (each 57.1%) and iucD (81.0%), and the operon sequence of Colicin V plasmids (38.1%). Some strains possessed toxin genes cdt-IIIB and cnf1/2 (both 14.3%), the invasion gene tia (23.8%), and the serine protease encoding gene espP (23.8%). Moreover, we could show that E. coli O78 strains under investigation were able to adhere to and invade MDBK-cells with varying efficiencies. The results indicate that the closely related O78 strains, constituting two major PFGE-clusters, harbor various virulence features for bovine intestinal disease but cannot be grouped into one of the common E. coli intestinal pathogenic or other pathotypes according to their virulence gene pattern. Nevertheless, the ability to adhere, invade or harbor toxin genes lets us suggest that O78 strains isolated from diarrheal cases in bovines urges further investigations on the zoonotic potential of these strains.

Animals↗
PubMed2004

Impact of the locus of enterocyte effacement pathogenicity island on the evolution of pathogenic Escherichia coli.

This review summarizes our current knowledge and models of appearance and dissemination of the locus of enterocyte effacement (LEE) within Escherichia coli phylogenetic lineages. The LEE is a pathogenicity island (PAI) required for attaching and effacing (A/E) lesion formation induced on epithelial cells of humans and animals by enteropathogenic and numerous enterohemorrhagic E. coli strains as well as other related bacteria. The LEE encodes a type III secretion system, an adhesin (intimin) responsible for the intimate attachment of the bacteria to the cell and a number of secreted proteins involved in signal transduction events. It has been shown that the LEE varies in size from 36 to 111 kb, depending on what E. coli lineages carrying that PAI. Three tRNA genes are known as LEE integration sites selC, pheU and pheV, the latter two are identical in sequence. Beneath its functional role, intimin is considered a phylogenetic marker of the LEE. Currently, 14 different intimin types have been described, designated alpha through ksi. Beta intimin-carrying LEEs moved within certain E. coli lineages from the pheU tRNA gene into the pheV tRNA gene. Moreover, as a result of the typing of multiple LEE core regions, the appearance of two different LEE cores indicates an import of the LEE within E. coli at least two times.

Adhesins, Bacterial↗
PubMed2003

National antibiotic resistance monitoring in veterinary pathogens from sick food-producing animals: the German programme and results from the 2001 pilot study.

In 2001, the first Germany comprehensive cross-sectional study into the sensitivity to antimicrobial substances of selected pathogenic bacteria from food-producing animal species (dairy cows, fattening pigs) was conducted by the Federal Office of Consumer Protection and Food Safety, BVL (formerly, Federal Institute for Health Protection of Consumers and Veterinary Medicine, BgVV). Initial experience from national resistance monitoring revealed that the necessary organisational structures may be suitably established in a federal system. The quantitative sensitivity results (minimum inhibitory concentration, MIC) for the bacterial species examined showed lower resistance values in contrast to German data published previously and also in comparison with results from other European countries. Based on the experience from this pilot study, an urgent need has been identified to continue this interdisciplinary approach to tackle the resistance problem together with human medicine. After analysing the data from the pilot monitoring study, in 2002 the BVL started a year's study with an extended selection of bacterial species and indications. In the future, bacterial samples from private diagnostic laboratories and universities will also be included in the resistance monitoring system.

Animals↗
PubMed2003

Dissemination of pheU- and pheV-located genomic islands among enteropathogenic (EPEC) and enterohemorrhagic (EHEC) E. coli and their possible role in the horizontal transfer of the locus of enterocyte effacement (LEE).

We have recently shown that the locus of enterocyte effacement (LEE) of the bovine enterohemorrhagic E. coli RW1374 (O103:H2) resides within a large pathogenicity island (PAI), integrated in the vicinity of the phenylalanine tRNA gene pheV. Here we describe an additional, but LEE-negative genomic island in RW1374 in the vicinity of another phenylalanine tRNA gene, pheU, the sequence of which is identical to pheV. These two genomic islands revealed identity of the left, but a relative variability of their right end sequences. To investigate the mechanism of LEE-PAI distribution in E. coli, we analysed similar junctions in the pheU/pheV loci of additional EPEC and EHEC strains the LEE location of which had not been determined before. By hybridisation of NotI restriction fragments with probes specific for LEE, pheV locus, and pheU locus, the LEE was found linked to either one of these two loci. The results agreed well with recently published phylogenetic data and indicate that in the clones of diarrheagenic E. coli (Dec) Dec 11 and Dec 12, forming the phylogenetic cluster EPEC 2, and in the strains of the most typical serotypes of the Dec 8, belonging to the phylogenetic cluster EHEC 2, the LEE was linked with pheV and not with the pheU locus as previously assumed. Sequence comparison with other pheU- and pheV-located genomic islands from different E. coli pathotypes (uropathogenic E. coli, septicemic E. coli) as well as from Shigella indicated the same structural features at the junctions. These conserved structures suggested a common DNA cassette, serving as common vehicle for horizontal gene transfer of various PAls. In addition, the elements suggest an origin from a common pheU-located ancestor and integration into the chromosome through site-specific recombination. Our results indicate that pheU/pheV-located genomic islands played an important role in the evolution of several PAls in E. coli and related pathogens.

Animals↗
PubMed2003

Description of a novel intimin variant (type zeta) in the bovine O84:NM verotoxin-producing Escherichia coli strain 537/89 and the diagnostic value of intimin typing.

Infections with verotoxin-producing Escherichia coli (VTEC) has resulted in increasing numbers of human illnesses annually. These illnesses usually result from the ability of VTEC to cause the attaching and effacing lesions (AE lesion). The AE phenotype is encoded by the locus of enterocyte effacement (LEE) pathogenicity island. A key adhesion factor involved is the outer membrane protein intimin, encoded by the eae gene within the LEE. Intimin types alpha, beta, gamma, delta, and epsilon have been described previously. Each intimin represents distinct phylogenetic lineages of LEE-positive strains. A new intimin type zeta was identified in a VTEC strain of the serotype O84:NM (nonmotile) that was isolated from a calf with diarrhea. zeta intimin showed the highest similarity (88%) of its amino acid sequence to the alpha intimin. For diagnostic purposes, we established a polymerase chain reaction (PCR) method for diagnosis of the key virulence traits of VTEC (i.e., verotoxins and intimins). This method also distinguishes between the toxins (VT1 and VT2) and the six intimin types. By applying the PCR method, intimin zeta in strains of other VTEC serotypes O84:H2, O92:NM, O119:H25, and O150:NM was identified. Because the intimin types represent distinctive phylogenetic E. coli lineages, application of the intimin subtyping PCR offers significant benefits. These include improving diagnosis of VTEC infection and increasing the understanding of evolution of attaching and effacing VTEC and other LEE-positive bacteria.

Adhesins, Bacterial↗
PubMed2003

Verotoxin 1 from Escherichia coli affects Gb3/CD77+ bovine lymphocytes independent of interleukin-2, tumor necrosis factor-alpha, and interferon-alpha.

Verotoxin (VT)-induced immunomodulation has been implicated in the ability of VT-producing Escherichia coli (VTEC) to cause persistent infections in cattle. VT1, also referred to as Shiga toxin 1, is a potent cytotoxin that modulates cytokine secretions and functions. This prompted the current investigation to examine whether the inhibiting effect of VT1 on bovine lymphocytes correlates with the expression of the cellular VT1 receptor Gb3/CD77 or is mediated instead via perturbation of cytokine secretion. Using blood mononuclear cells stimulated by mitogens as a model, VT1 significantly blocked lymphoblast transformation and proliferation in the BoCD8+ T cell and BoCD21+ B cell population. In contrast, VT1 dramatically reduced the number of viable Gb3/CD77+ blast cells within all subpopulations identified (BoCD2+, BoCD4+, BoCD8+, WC1+ [i.e., gammadelta T cells] BoCD21+, and BoCD25+). Similar effects of VT1 were observed when the culture medium was supplemented with selected cytokines: tumor necrosis factor-alpha-sensitizing endothelial cells against VT1, interferon-alpha (IFN-alpha) as bovine IFN-alpha receptors are partially homologous to the B-subunit of VT1, and interleukin-2 that is critical for lymphocyte proliferation in vitro. The addition of these cytokines was neither able to mimic nor to overcome the effects of VT1. Therefore, it is concluded that VT1 directly acts on bovine lymphocytes rather than inducing a cytokine-mediated effect. VT1 considerably affects all main bovine lymphocyte subpopulations, implicating that the immune system is a predominant target for VT1 in cattle.

Animals↗
PubMedDate not supplied

[Avian pathogenic Escherichia coli (APEC)].

Infections with avian pathogenic Escherichia coli (APEC) cause colibacillosis, an acute and mostly systemic disease resulting in significant economic losses in poultry industry worldwide. Avian colibacillosis is a complex syndrome characterized by multiple organ lesions with airsacculitis and associated pericarditis, perihepatitis and peritonitis being most typical. Environmental factors as well as the constitution of poultry or initial viral infections influence the outcome of APEC-infections. However, several challenge experiments in chickens proofed the role of virulent APEC strains as the single aetiological agent. Currently serotypes O1:K1, O2:K1 and O78:K80 are recognized as the most prevalent, however the number of published serotypes is increasing. In addition, single APEC isolates vary profoundly in virulence, and knowledge about the molecular basis of this variability is still scarce. Known virulence factors of APEC are adhesins (F1- and P-fimbriae), iron acquisition systems (aerobactin and yersiniabactin), hemolysins (hemolysinE and temperaturesensitive hemagglutinin), resistance to the bactericidal effects of serum and phagocytosis (outer membrane protein, iss protein, lipopolysaccharide, K/1)-capsule and colilcin production) as well as toxins and cytotoxins (heat stable toxin, cyto-/verotoxin and flagella toxin). Esperimental studies have shown that the respiratory tract, principally the gas-exchange region of the lung and the interstitium of the air sacs are the most important sites of entry for avian pathogenic E. coli. APEC strains adhere to the epithelial cells of air sacs presumably through F1-fimbriae. After colonization and multiplication the bacteria enter the bloodstream, and the temperature-sensitive hemagglutinin (tsh) seems to be important int his step. After invading the bloodstream APEC cause a septicemia resulting in massive lesins in multiple internal organs and in sudden death of the birds. The ability of the bacteria to acquire iron and the resistance to the bactericidal effects of serum, predominantly conferred by the increased serum survival (iss)--protein, enables APEC to multiply quickly in their hosts. Iss is regarded a specific genetic marker for avian pathogenic E. colistrains. A critical review of the literature published so far on APEC reveals, that these pathotypes are not defined appropriately. This findings urge investigations on the population structure of APEC, enabling the establishment of appropriate diagnostic tools and avoiding the obsolete use of serotyping for APEC diagnosis. So far more than 20 APEC strains have been investigated in animal experiments, explaining contrary published results. Thus, the lack of knowledge in pathogenicity and in immunity of APEC infections urges further experimental studies. As APEC share not only identical serotypes with human pathogens but also specific virulence factors, their zoonotic potential is under consideration.

Adhesins, Escherichia coli↗
PubMedDate not supplied

[Editorial].

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Animals↗
PubMedDate not supplied

[Mannheimia haemolytica and the pathogenesis of enzootic bronchopneumonia].

Mannheimia (M.) haemolytica (formerly Pasteurella [P.] haemolytica) is the primary aetiological agent of pneumonic pasteurellosis--one of the most important respiratory diseases in cattle and sheep. While bovine pneumonic pasteurellosis is regarded to be mainly caused by M. haemolytica serotype A1, and in Germany during the last years also by serotype A6, sheep can be infected by all serotypes although there is an increased prevalence of serotypes A2 and A5-7. The obligate pathogenicity of M. haemolytica is proven by isolation of pure cultures from pneumonic lungs as well as by infection studies. Knowledge about the virulence mechanisms of M. haemolytica and their molecular basis are fragmentary, most probably due to the complex gene regulation of virulence associated factors in lung tissues. This review summarizes the current literature covering virulence factors to substantiate a model of pathogenesis. After serotype A1 strains have colonized the bovine upper respiratory tract they replace other serotypes by mechanisms unknown to date. After fulminant proliferation in the upper respiratory tract the microorganisms colonize the lower respiratory tract, finally entering alveolar spaces. An inflammatory cascade is initiated by M. haemolytica LPS and Leukotoxin, causing activation of the complement system and release of cytokines. Pathognomonic for bovine pneumonic pasteurellosis is the strong influx of neutrophiles accompanied by accumulation of fibrin, finally causing necrosis of alveolar spaces. Depending on lesion size this fibronecrotizing pneumonia can result in death of the animals. In addition, possible protective antigens are discussed. There is still a great effort in the development of efficacious vaccines against pneumonic pasteurellosis in cattle and sheep caused by various M. haemolytica serotypes worldwide. The scarce knowledge concerning presence and distribution of virulence associated factors in M. haemolytica strains and their role in pathogenesis made it difficult to determine a suitable vaccine candidate in the past. In addition, there is lack of knowledge concerning the variability of virulence factors in individual isolates. Genome sequence analysis of M. haemolytica, enabling proteomics and transciptomics, hopefully will give new insight into the pathogenesis of pneumonic pasteurellosis.

Animals↗
PubMedDate not supplied

[Plasticity of bacterial genomes: pathogenicity islands and the locus of enterocyte effacement (LEE)].

Many bacterial virulence attributes, like toxins, adhesins, invasins, iron uptake systems, are encoded within specific regions of the bacterial genome. These in size varying regions are termed pathogenicity islands (PAIs) since they confer pathogenic properties to the respective micro-organism. Per definition PAIs are exclusively found in pathogenic strains and are often inserted near transfer-RNA genes. Nevertheless, non-pathogenic bacteria also possess foreign DNA elements that confer advantageous features, leading to improved fitness. These additional DNA elements as well as PAIs are termed genomic islands and were acquired during bacterial evolution. Significant G+C content deviation in pathogenicity islands with respect to the rest of the genome, the presence of direct repeat sequences at the flanking regions, the presence of integrase gene determinants as other mobility features,the particular insertion site (tRNA gene) as well as the observed genetic instability suggests that pathogenicity islands were acquired by horizontal gene transfer. PAIs are the fascinating proof of the plasticity of bacterial genomes. PAIs were originally described in human pathogenic Escherichia (E.) coli strains. In the meantime PAIs have been found in various pathogenic bacteria of humans, animals and even plants. The Locus of Enterocyte Effacement (LEE) is one particular widely distributed PAI of E coli. In addition, it also confers pathogenicity to the related species Citrobacter (C.) rodentium and Escherichia (E.) alvei. The LEE is an important virulence feature of several animal pathogens. It is an obligate PAI of all animal and human enteropathogenic E. coli (EPEC), and most enterohaemorrhegic E. coli (EHEC) also harbor the LEE. The LEE encodes a type III secretion system, an adhesion (intimin) that mediates the intimate contact between the bacterium and the epithelial cell, as well as various proteins which are secreted via the type III secretion system. The LEE encoded virulence features are responsible for the formation of so called attaching and effacing (AE) lesions in the intestinal epithelium. Due to its wide distribution in animal pathogens, LEE encoded antigens are suitable vaccine antigens. Acquisition and structure of the LEE pathogenicity island is the crucial point of numerous investigations. However, the evolution of the LEE, its origin and further spread in E. coli, are far from being resolved.

Bacteria↗
PubMedDate not supplied

["Risk analysis"].

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Animals↗
PubMedDate not supplied

[Risk assessment of bluetongue disease incursion into Germany using geographic information system (GIS)].

Using a geographic information system (GIS), by analysis of the relationship between the spatial distribution of cattle density and the risk factors temperature, altitude and rainfall, we defined geographical habitats enabling optimal development and competence of Culicoides spp. to transmit Bluetongue-Virus (BTV): Risk zones (low, high, highest risk) were identified mainly in Baden-Württemberg, Hessen and Rheinland-Pfalz if persistently infected ruminants are imported into these zones in summer (June to August mainly), based on the current climatic conditions, BTD outbreaks are considered a real possibility. Overwintering of the virus seems unlikely. However, global warming will lead to a steady increase of the size of the risk zones. In addition, the possibility of primary outbreaks increases. The reason for this is not only the expected northern shift of Culicoides imicola, but in addition an increasing vector competence of domestic Culicoides species. We therefore recommend the storage of vaccines as well as conducting ecological studies analysing the presence of Culicoides vectors. Using the data from these studies, it will be possible to produce updated quantitative risk assessment via GIS.

Animals↗
PubMedDate not supplied

[Pasteurella: insights into the virulence determinants of a heterogenous bacterial type].

Pasteurella (P.) multocida is the causative agent of numerous economically relevant diseases worldwide. These are enzootic bronchopneumonia in cattle and sheep and hemorraghic septicemia in cattle and buffaloes, Rhinitis atrophicans in swine, snuffles in rabbit, and fowl cholera. All disease complexes are associated with certain capsular and somatic antigens. Even as human pathogen P. multocida is of increasing importance, causing wound infections, and even septicemia, meningitis, and endocarditis. Despite extensive research activities including the genome analysis of one fowl cholera isolate in the year 2001 there are a lot of open questions concerning the molecular pathogenic mechanisms. Problems encountered are the high antigenic variability and the wide host spectrum of P. multocida as well as different courses of infection. In consequence there are enormous difficulties in producing vaccines. Transcriptomics and proteomics hopefully will give new insight into the pathogenesis of P. multocida infections in different hosts. A frequent problem particular in classical diagnostic laboratories is the diagnosis of P. multocida and its differentiation from other P. species and Mannheimia (M.) haemolytica. The biochemical identification of P. multocida is not reliable due to variable phenotypical characteristics often caused by different culture conditions, and it is time consuming and cost-intensive. Extensive molecular biologic studies concerning the prevalence and distribution of virulence associated genes known so far in P. species, which will be described in detail in this paper, could contribute to the establishment of a diagnostic tool, such as a multiplex polymerase chain reaction, that would provide a cheap and time-saving identification and characterization of wildtype strains.

Animal Diseases↗