Characterization and prediction of the mechanism of action of antibiotics through NMR metabolomics

Background: The emergence of antibiotic resistant pathogenic bacteria has reduced our ability to combat infectious diseases. At the same time the numbers of new antibiotics reaching the market have decreased. This situation has created an urgent need to discover novel antibiotic scaffolds. Recently, the application of pattern recognition techniques to identify molecular fingerprints in ‘omics’ studies, has emerged as an important tool in biomedical research and laboratory medicine to identify pathogens, to monitor therapeutic treatments or to develop drugs with improved metabolic stability, toxicological profile and efficacy. Here, we hypothesize that a combination of metabolic intracellular fingerprints and extracellular footprints would provide a more comprehensive picture about the mechanism of action of novel antibiotics in drug discovery programs. Results: In an attempt to integrate the metabolomics approach as a classification tool in the drug discovery processes, we have used quantitative 1H NMR spectroscopy to study the metabolic response of Escherichia coli cultures to different antibiotics. Within the frame of our study the effects of five different and well-known antibiotic classes on the bacterial metabolome were investigated both by intracellular fingerprint and extracellular footprint analysis. The metabolic fingerprints and footprints of bacterial cultures were affected in a distinct manner and provided complementary information regarding intracellular and extracellular targets such as protein synthesis, DNA and cell wall. While cell cultures affected by antibiotics that act on intracellular targets showed class-specific fingerprints, the metabolic footprints differed significantly only when antibiotics that target the cell wall were applied. In addition, using a training set of E. coli fingerprints extracted after treatment with different antibiotic classes, the mode of action of streptomycin, tetracycline and carbenicillin could be correctly predicted. Conclusion: The metabolic profiles of E. coli treated with antibiotics with intracellular and extracellular targets could be separated in fingerprint and footprint analysis, respectively and provided complementary information. Based on the specific fingerprints obtained for different classes of antibiotics, the mode of action of several antibiotics could be predicted. The same classification approach should be applicable to studies of other pathogenic bacteria

Literatur-Rundschau

Ursula Rautenberg (Hg.): Reclams Sachlexikon des Buches (Walter Hömberg) Andreas Greis/ Gerfried W. Hunold/ Klaus Koziol (Hg.): Medienethik. Ein Arbeitsbuch Bemhard Debatin/Rüdiger Funiok (Hg.): Kommunikations- und Medienethik (Lars Rademacher) Ludger Verst: MedienpastoraL Bericht über ein Projekt (Susanne Haverkamp) Alexander Seibold: Katholische Filmarbeit in der DDR. "Wir haben eine gewisse Pfiffigkeit uns angenommen." (Peter Hasenberg) Michael Schenk: Medienwirkungsforschung. 2., vollständig überarbeitete Auflage (Hermann-Josef Große-Kracht) Ralf Hohlfeld: Joumalismus und Medienforschung. Theorie, Empirie, Transfer (Gabriele Siegert) Margaretha Ramm u.a.: Berufs- und Karriereplaner Medien und Kommunikation 2003/2004 (Steffen Hillebrecht) Peter Huemer: Warum das Fernsehen dümmer ist als das Radio. Reden über das Reden in den Medien (Verena Blaum) Richard W. Dill: Neue Demokratien – neuer Rundfunk. Erfahrungen mit der Medientransformation in Osteuropa (Klaus Brodbeck)Sten Nadolny: Ullsteinroman (Markus Behmer

The Asexual Pathogen Aspergillus fumigatus Expresses Functional Determinants of Aspergillus nidulans Sexual Development▿

The major fungal pathogen of humans, Aspergillus fumigatus, lacks a defined sexual cycle, although the presence of genes encoding putative mating type idiomorphs and regulators of Aspergillus sexual development heightens the potential for cryptic sexuality in this deuteromycete. To test the functionality of these genetic determinants, we transferred the alpha box-encoding mat1-1 idiomorph from an A. fumigatus isolate to the homothallic fertile species Aspergillus nidulans. Abundant formation of fruiting bodies (cleistothecia) containing viable ascospores establishes functionality of this mating type gene product in the transgenic strain. Using a similar approach, we also established that the conserved transcriptional regulator from A. fumigatus, the nsdD gene product, can act as a functional, positively acting factor for A. nidulans cleistothecium development; moreover, high-level expression of NsdD in the endogenous host A. fumigatus profoundly alters hyphal development by triggering the formation of coiled hyphae. Our findings demonstrate that the presumably asexual pathogen A. fumigatus encodes functional regulators of mating and sexual development, thereby potentiating the case for cryptic sexuality in this fungal pathogen

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Gasper, Müller, Valentin (Hg.): Lexikon der Sekten I Schiwy, Schütz (Hg.): Medienrecht, Lexikon für Wissenschaft und Praxis I Baacke, Sander, Vollbrecht: Lebenswelten sind Medienwelten I Jarocki: 45 Jahre in der Opposition I Kalt: (Hg.) Wirtschaft in den Medien I Altschull: Agenten der Macht I Grossenbacher: Die Medienmacher I Die Landesmedienanstalten, DLM-Jahrbuch 1989190 (Privater Rundfunk in Deutschland) I Jenny: 111 Jahre Nebelspalter I Zielinski: Zur Geschichte des Videorecorders I Gounalakis: Kabelfernsehen im Spannungsfeld von Urheberrecht und Verbraucherschutz

Effect of whole acorns (<i>Quercus pubescens</i>) shred based diet on parotid gland in growing pigs in relation to tannins

The amounts and composition of saliva produced in parotid glands can be influenced by dietary biologically active substances. Among phenolic compounds naturally present in some feedstuffs, particularly condensed tannins and hydrolysable tannins and derivates appear to play a role for the induction of Proline Rich Protein secretion in the parotid saliva of some animal species: this might be considered as a first evolutionary defence mechanism against the protein precipitating activity of tannins, preferably bond to proline and histatins in saliva. This is the first paper to report the preliminary results on the effects of full ripe acorns (Q. pubescens) polyphenols measured as Tannic Acid Equivalents on the parotid gland of growing pigs. A total of 8 growing pigs were divided into 2 experimental groups (each n = 4): the control group was fed a conventional complete diet for pigs (pelleted; 890 g DM/kg; based on cereals and soybean extraction meal). The acorn-fed group was offered a combined diet, 70% of ripe whole acorns shred (612 g DM/kg of fresh matter, 0.516 g TAE/kg DM) and 30% of the complete diet. One additional pig was fed the experimental diet for 24 h only. All 8 animals from the 2 experimental groups were sacrificed at 1 week after consumption, the additional pig, 24 h after consumption. Both parotid glands of each pig were removed and weighed. Maximum length and width were measured and the right parotids were used in toto to determine dry matter, crude protein and total proline content. Each left parotid gland was processed for microscopic check. Increased size (+ 53.8% length; + 19.9% width), mass (+ 68.5% fresh weight) and proline content (+ 33.8% based on DM) were observed in animals fed the 70% acorns diet after 7 days. These results inspire to perform further investigations on the rapid adaption of pigs to counteract the effects of tannins in whole acorns as found after only one day of exposure

Improved visualization of hypodense liver lesions in virtual monoenergetic images from spectral detector CT: Proof of concept in a 3D-printed phantom and evaluation in 74 patients.

OBJECTIVES The well-known boost of iodine associated-attenuation in low-keV virtual monoenergetic images (VMI_low) is frequently used to improve visualization of lesions and structures taking up contrast media. This study aimed to evaluate this concept in reverse. Hence to investigate if increased attenuation within the liver allows for improved visualization of little or not-enhancing lesions. METHODS A 3D-printed phantom mimicking the shape of a human liver exhibiting a lesion in its center was designed and printed. Both, parenchyma- and lesion-mimic were filled with different solutions exhibiting 80/100/120HU and 0/15/40/60HU, respectively. Further, a total of 74 contrast-enhanced studies performed on a spectral detector CT scanner (SDCT) were included in this retrospective study. Patients had MRI or follow-up proven cysts and/or hypodense metastases. VMI of 40-200 keV as well as conventional images (CI) were reconstructed. ROI were placed in lesion and parenchyma(-mimics) on CI and transferred to VMI. Signal- and contrast-to-noise ratio were calculated (S-/CNR). Further, two radiologists independently evaluated image quality. Data was statistically assessed using ANOVA or Wilcoxon-test. RESULTS In phantoms, S/CNR was significantly higher in VMI_low. The cyst-mimic in highly attenuating parenchyma-mimic on CI yielded a CNR of 6.4 ± 0.8; using VMI_40 keV, mildly hypodense lesion-mimic in poorly attenuating parenchyma-mimic exhibited a similar CNR (5.8 ± 0.9; p ≤ 0.05). The same tendency was observed in patients (cyst in CI/metastasis in VMI_40 keV: 4.4 ± 1.2/3.9 ± 1.8; p ≤ 0.05). Qualitative analysis indicated a benefit of VMI_40 keV (p ≤ 0.05). CONCLUSIONS VMI_low from SDCT allow for an improved visualization of hypodense focal liver lesions exploiting the concept of contrast blooming in reverse

Virtual non-contrast for evaluation of liver parenchyma and vessels: results from 25 patients using multi-phase spectral-detector CT.

Background In abdominal imaging, contrast-enhanced computed tomography (CT) examinations are most commonly applied; however, unenhanced examinations are still needed for several clinical questions but require additional scanning and radiation exposure. Purpose To evaluate accuracy of virtual non-contrast (VNC) from arterial and venous phase spectral-detector CT (SDCT) scans compared to true-unenhanced (TNC) images for the evaluation of liver parenchyma and vessels. Material and Methods A total of 25 patients undergoing triphasic SDCT examinations were included. VNC was reconstructed from arterial and venous phases and compared to TNC images. Quantitative image analysis was performed by region of interest (ROI)-based assessment of mean and SD of attenuation (HU) in each liver segment, spleen, portal vein, common hepatic artery, and abdominal aorta. Subjectively, iodine subtraction and diagnostic assessment were rated on 5-point Likert scales. Results Attenuation and image noise measured in the liver from VNC were not significantly different from TNC (TNC: 54.6 +/- 10.8 HU, VNC arterial phase: 55.7 +/- 10.8 HU; VNC venous phase: 58.3 +/- 10.0 HU; P > 0.05). VNC also showed accurate results regarding attenuation and image noise for spleen, portal vein, and abdominal aorta. Only iodine subtraction in the common hepatic artery in the arterial phase was insufficient which was confirmed by the subjective reading. Apart from that, subjective reading showed accurate iodine subtraction and comparable diagnostic assessment. Conclusion VNC from the arterial and venous phases were very similar to TNC yielding mostly negligible differences in attenuation, image noise, and diagnostic utility. Inadequate iodine subtraction occurred in hepatic arteries in the arterial phase

CT artifacts after contrast media injection in chest imaging: evaluation of post-processing algorithms, virtual monoenergetic images and their combination for artifact reduction

Background: After injection into a brachial vein, high contrast media concentration in axillary and subclavian veins can cause artifacts that impair diagnostic utility. This study assessed artifact reduction by artifact-reduction-algorithms (ARA) and virtual-monoenergetic-images (VMI), as well as their combination (VMIARA) compared to conventional CT-images (CI). Methods: Forty-six spectral-detector-CT (SDCT) examinations of patients that received ARA-reconstructions due to perivenous-artifacts were included in this retrospective study. CI, ARA, VMI, and VMIARA (range: 70-200 keV) were reconstructed. Objective analysis was performed with ROI-based assessment of mean and standard deviation of attenuation (HU) in hypo- and hyperdense artifacts and impaired muscle and arteries as well as artifact-free reference-tissue. Extent of artifact reduction, assessment of surrounding soft tissue and vessels, and appearance of new artifacts were rated visually by two radiologists. Results: Hypo- and hyperdense artifacts showed significant improvement as evidenced by decreasing attenuation differences between artifact impaired and artifact-free reference tissue in ARA, VMI ≥80 keV, and VMIARA between 70-200 keV (e.g., CI/ARA/VMI100keV/VMIARA100keV: hypodense artifacts, (-)264.8±150.9/(-)87.1±78.9/(-)48.6±64.6/9.9±63.9 HU; P<0.001); hyperdense artifacts, 164.2±51.1/82.1±73.2/7.9±34.7/(-)17.3±50.7 HU; P<0.001). Artifacts impairing surrounding muscle and arteries were also reduced by all three approaches. In visual assessment, ARA, VMI ≥100 keV, and VMIARA between 70-200 keV also showed significant artifact reduction and improved assessment; however, for assessment of arteries improvement was not significant using ARA alone. New artifacts were reported, particularly at higher keV-values. Conclusions: In presence of perivenous-artifacts, ARA, VMI and their combination allow for significant artifact reduction; however, their combination and VMI as a standalone approach yielded best results and should therefore be used, if available. Keywords: X-ray computed tomography; algorithms; artifacts; contrast media; dual-energy CT; spectral-detector CT (SDCT)