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Günter Klein

Publications and source records attributed to Günter Klein.

12 recordsLinked to original sources
PubMed2005

The Ni-mediated cyclocarbonylation of allyl halides and alkynes made catalytic. Evidence supporting the involvement of pseudoradical Ni(i) species in the mechanism.

We report here on a highly efficient catalytic method to synthesize intermolecularly the cyclopentane skeleton from starting products as simple as allyl halides, alkynes, and carbon monoxide under very mild reaction conditions by means of a substoichiometric amount of iron, acetone, and a catalytic amount of Ni(II) iodide.

Journal Article↗
PubMed2003

Taxonomy, ecology and antibiotic resistance of enterococci from food and the gastro-intestinal tract.

Apart from genotypic identification methods, there is a need for reliable conventional phenotypic identification schemes for simple and rapid determination of enterococcal species in food or in the gastro-intestinal tract (GIT). Only a limited number of enterococcal species is of importance for the ecology of the GIT or the food microflora, including E. faecalis, E. faecium, E. durans/hirae, E. gallinarum and E. casseliflavus. After genus identification the differentiation within these species can include, e.g. mannitol and arabinose fermentation and growth at 50 degrees C. Widely used commercial identification systems may fail to precisely identify rare species. Ecological aspects should also be taken into account. In the human GIT E. faecium is the most common species whereas in most animal species E. faecalis is at least present in the same amount. Especially in foods of animal origin (cheese, pork meat, beef, poultry meat) also E. faecalis is very frequent. This is of special interest as glycopeptide resistance is most often found in human clinical E. faecium strains as well as in E. faecium from the environment or animal samples and less frequent in E. faecalis strains. EU experts propose as safety criteria for probiotics in feed additives the exclusion of resistances or the lack of transferability. This proposal can also be applied to enterococci in foods. Specific resistances must be excluded, but transferability or acquisition of resistance (e.g. vancomycin) cannot be excluded per se. However, technologically used strains should differ from clinical strains concerning their resistance patterns and transfer rates.

Anti-Bacterial Agents↗
PubMed2003

Species distribution and antibiotic resistance patterns of enterococci isolated from food of animal origin in Germany.

Presently, enterococci take the third place of bacterial pathogens associated with nosocomial infections, after staphylococci and Escherichia coli. Especially, the resistances of enterococci to several available antibiotics are threatening. We attempted to determine which species of enterococci could be found in food of animal origin and their significance according to their antibiotic resistances for human beings. From November 2000 to May 2002 we investigated 155 samples of food of animal origin bought in retail outlets in Germany: 27 samples of sausages, 19 of ham, 83 of minced meat, 26 of cheese. From these food samples we isolated 416 enterococcal strains. The most frequent species was Enterococcus faecalis (299 strains); furthermore, we found Enterococcus faecium (54 strains), Enterococcus durans together with Enterococcus hirae (24 strains), Enterococcus casseliflavus (22 strains), Enterococcus avium (9 strains) and Enterococcus gallinarum (8 strains). We focused on the resistance patterns of 118 selected E. faecium and E. faecalis strains to 13 antimicrobial active agents (ampicillin, amoxicillin/clavulanic acid, avilamycin, chloramphenicol, enrofloxacin, erythromycin, flavomycin, gentamicin, penicillin, quinupristin/dalfopristin, teicoplanin, tetracycline and vancomycin). From the clinical point of view, the situation of antibiotic resistance to the examined antimicrobial agents seemed to be favourable. The investigated strains were sensitive to ampicillin and amoxicillin/clavulanic acid. These antibiotics are, in combination with an aminoglycoside, for example gentamicin, agents of choice for the treatment of enterococcal infections in human medicine. Only one E. faecium strain was resistant to penicillin, while all strains were sensitive to the glycopeptide antibiotics, vancomycin and teicoplanin. Resistances found against the antibiotics, tetracycline, quinupristin/dalfopristin and erythromycin, are causes for concern.

Animals↗
PubMedDate not supplied

[Antimicrobial susceptibility testing of bacteria isolated from animals: methods for in-vitro susceptibility testing and their suitability with regard to the generation of the most useful data for therapeutic applications].

In-vitro susceptibility testing provides valuable informations for choosing the most suitable antimicrobial agent for the control of bacterial infections in animals. Different diffusion and dilution methods, as conducted according to various approved performance standards, can be used to determine the in-vitro susceptibility of bacterial pathogens. In the present article, problems are discussed which arise from the use of different methods and the difficulty to interpret such results. While most approved performance standards were designed for testing of bacteria from human sources, the NCCLS document M31-A2 exclusively focusses on susceptibility testing of bacteria isolated from animals and--in contrast to all other standards--includes veterinary specific breakpoints for a number of antimicrobial agents used in veterinary medicine. Therefore, performance of in-vitro susceptibility testing of veterinary pathogens should follow the recommendations given in the NCCLS document M31-A2. The microdilution method is recommended as the method of choice for susceptibility testing. The result of a microdilution test is given as the minimum inhibitory concentration (MIC). This value provides a quantitative result which precisely indicates the degree of susceptibility of the tested bacterial strain and in return gives the veterinarian a clear guidance whether therapeutic intervention with the antibiotic in question will be successful.

Animals↗
PubMedDate not supplied

[Suitability of SSCP-PCR analysis for molecular detection of quinolone resistance in Campylobacter jejuni].

Foodborne infections with Campylobacter spp. are increasing, especially antibiotic resistant strains are emerging. Quinolone resistant isolates can cause failure of therapy in severe clinical infections. Molecular characterisation is needed for the detection of resistant variants of C. jejuni. Therefore 23 isolates from poultry and human medicine as well as three control strains were tested for their minimal inhibitory concentration, their Single-Strand-Conformation-Polymorphism (SSCP)-PCR pattern (a method for the detection of resistance determining point mutations), and their sequence of the quinolone resistance determining region (QRDR). Six different SSCP types could be identified: two types for quinolone resistant isolates and other types containing so called silent mutations without influence on the resistance. A genotypic monitoring of the quinolone resistance in C. jejuni can be useful for the early detection of new resistance variants. As a screening method for detection of point mutations in the QRDR the SSCP-PCR can be applied. Compared to other genotypic methods the SSCP-PCR is less time and cost consuming and needs only standard technical equipment.

Animals↗
PubMedDate not supplied

[Use of molecular methods in food microbiology with the example of probiotic use of lactobacilli].

The aim of molecular methods in food microbiology is the identification or strain specific differentiation of microorganisms. Identification methods include besides taxonomic purposes also the detection of virulence genes or resistance markers. Strain specific differentiation is used for epidemiological investigations or the quality control of technologically used bacteria. Probiotic strains of the Lactobacillus acidophilus-group were investigated with different molecular methods: for identification proteinfingerprinting and RAPD-PCR (Random Amplified Polymorphic DNA-PCR) were applied, for strain specific differentiation pulsed field gel electrophoresis (PFGE) and again RAPD-PCR were used. The molecular methods applied should be chosen depending on the objective (identification, differentiation) and with respect to the organism to be tested. In case of probiotic lactic acid bacteria like the L. acidophilus-group proteinfingerprinting has proved to be successful for identification and with some limitation also RAPD-PCR. For differentiation PFGE is suitable as well as RAPD-PCR. Those methods differ substantially in their work load and in personal requirements, and show different power of discrimination and reproducibility within and between laboratories. This should be considered while choosing the appropriate method.

DNA, Bacterial↗
PubMedDate not supplied

[Editorial].

Explore the source record for details and available documents.

Animals↗
PubMedDate not supplied

[Proposals of the working group "Antibiotic resistance" for the configuration of microtitre plates to be used in routine antimicrobial susceptibility testing of bacterial pathogens from infections of large food-producing animals and mastitis cases].

Two layouts for microtitre plates, which should serve for in-vitro susceptibility testing in routine diagnostics, have been set up by the working group "Antibiotic resistance" of the German Society for Veterinary Medicine. One of these layouts was designed for the testing of bacteria from cases of mastitis and the other for bacteria from infections in large food-producing animals. The choice of the antimicrobial agents and their concentrations to be included in these layouts were based on (1) the bacteria frequently associated with the respective diseases/animals, (2) the antimicrobial agents licensed for therapeutic use in these diseases/animals, (3) the currently available breakpoints, and (4) cross-resistances between the antimicrobial agerts so far known to occur in the respective bacteria.

Animals↗
PubMedDate not supplied

[Results from a German interlaboratory test to establish the broth microdilution method for the determination of the minimum inhibitory concentration of bacteria from animals].

In accordance with NCCLS guideline M31-A2, the DVG working group "antimicrobial resistance" developed a standard operating procedure (SOP) for the determination of the minimal inhibitory concentration (MIC) of antimicrobial agents by broth microdilution. This SOP was evaluated for its fitness for use in a national interlaboratory test. A total of 32 participating laboratories tested five strains (including two internationally accepted reference strains and three field strains representing in total three different bacterial species) three times at a one week interval each, using uniform microtitre plates. In 31 of the 32 laboratories more than 80% of MIC determinations performed yielded values in the expected range. In total 94.0% of the results were reproducible, with a lesser deviation of 4.0% from the expected values for laboratories performing MIC determination as a matter of routine (46.9%), compared to 7.9% for laboratories without such routine (53.1%). Comparing the consistency of results on the basis of the tested strains, a higher reproducibility of the results was observed for reference strains (96.1%) than for field strains (92.6%). In particular results obtained for the Streptococcus uberis field strain were afflicted with a higher error ratio (98 deviations from the expected values). Among the tested antimicrobial agents, a higher variability of results was recorded only for gentamicin with 16.7% divergent MIC determinations (mean value 6.0%). The high reproducibility of the results confirmed by this interlaboratory study underlines the robustness of the developed SOP as well as broth microdilutions as the method of choice for MIC determina tion.

Animals↗
PubMedDate not supplied

[Resistance of mastitis pathogens in northern Germany].

The data of 1692 susceptibility tests acquired from April 2003 through March 2004 in the mastitis laboratory of the Institute for Food Quality and Safety were summarized in order to help veterinarians confronted with acute mastitis in choosing the appropriate antibiotic. Two thirds of the milk samples were infected with gram-positive cocci. One third of these were identified as Streptococcus (S.) uberis, one fourth as Staphylococcus (S.) aureus. All isolates (100%) of S. uberis, S. dysgalactiae, S. agalactiae and Arcanobacterium pyogenes were susceptible to Penicillin and Ampicillin. Concering S. aureus, nearly 100% of the isolates were susceptible to Oxacillin, Cephalothin, Cefacetril, Cefquinom and Neomycin, but only 88% of the isolates were sensitive to Penicillin, Ampicillin and Cefoperazon. The gram-negative rods (Escherichia (E.) coli, Klebsiella spp. and Pseudomonas spp.) displayed an irregular resistance pattern. More than 93% of all examined isolates including Pseudomonas spp. were susceptible to Colistin. The sensitivity of E. coli and Klebsiella spp.to Marbofloxacin, Enrofloxacin and Cefquinom exceeded 96%. Thus, the susceptibility of gram-positive mastitis pathogens to common antibiotics is favourable. Because the highly effective Colistin is no longer approved for local therapy, the situation for gram-negative bacteria is more difficult.

Animals↗
PubMedDate not supplied

[Cross-resistance between antimicrobial agents used in veterinary medicine: molecular background and practical consequences for susceptibility testing].

Phenotypic resistance of veterinary pathogens to more than one antimicrobial agent (multi-resistance) may be caused by intrinsic resistance to the antimicrobial agents, acquired cross-resistance, or acquired co-resistance. Known cross-resistances allow to select so-called "representative substances" which are tested and the results of which can also be regarded as being valid for other members of the same class of antimicrobial agents. In general, a limitation in the number of antimicrobial agents to be tested in routine diagnostics is necessary because of capacity and cost efficiency. This is of particular relevance when the broth microdilution method - recommended as the method of choice - with 96-well microtiter plates is used. The knowledge about the relationship between different resistance phenotypes and the corresponding resistance mechanisms is of major value for both, the laboratory personnel and the veterinary practitioner. This review explains how "representative substances" for the most relevant classes of antimicrobial agents used in veterinary medicine are chosen on the basis of known cross-resistances.

Animals↗