Recent Submissions

  • Discovery of Staphylococcus aureus Adhesion Inhibitors by Automated Imaging and Their Characterization in a Mouse Model of Persistent Nasal Colonization.

    Fernandes de Oliveira, Liliane Maria; Steindorff, Marina; Darisipudi, Murthy N; Mrochen, Daniel M; Trübe, Patricia; Bröker, Barbara M; Brönstrup, Mark; Tegge, Werner; Holtfreter, Silva; HZI,Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7,38124 Braunschweig, Germany. (MDPI, 2021-03-18)
    Due to increasing mupirocin resistance, alternatives for Staphylococcus aureus nasal decolonization are urgently needed. Adhesion inhibitors are promising new preventive agents that may be less prone to induce resistance, as they do not interfere with the viability of S. aureus and therefore exert less selection pressure. We identified promising adhesion inhibitors by screening a library of 4208 compounds for their capacity to inhibit S. aureus adhesion to A-549 epithelial cells in vitro in a novel automated, imaging-based assay. The assay quantified DAPI-stained nuclei of the host cell; attached bacteria were stained with an anti-teichoic acid antibody. The most promising candidate, aurintricarboxylic acid (ATA), was evaluated in a novel persistent S. aureus nasal colonization model using a mouse-adapted S. aureus strain. Colonized mice were treated intranasally over 7 days with ATA using a wide dose range (0.5-10%). Mupirocin completely eliminated the bacteria from the nose within three days of treatment. In contrast, even high concentrations of ATA failed to eradicate the bacteria. To conclude, our imaging-based assay and the persistent colonization model provide excellent tools to identify and validate new drug candidates against S. aureus nasal colonization. However, our first tested candidate ATA failed to induce S. aureus decolonization.
  • A New PqsR Inverse Agonist Potentiates Tobramycin Efficacy to Eradicate Pseudomonas aeruginosa Biofilms

    Schütz, Christian; Ho, Duy‐Khiet; Hamed, Mostafa Mohamed; Abdelsamie, Ahmed Saad; Röhrig, Teresa; Herr, Christian; Kany, Andreas Martin; Rox, Katharina; Schmelz, Stefan; Siebenbürger, Lorenz; et al. (Wiley and Sons Inc., 2021-03-18)
    Pseudomonas aeruginosa (PA) infections can be notoriously difficult to treat and are often accompanied by the development of antimicrobial resistance (AMR). Quorum sensing inhibitors (QSI) acting on PqsR (MvfR) – a crucial transcriptional regulator serving major functions in PA virulence – can enhance antibiotic efficacy and eventually prevent the AMR. An integrated drug discovery campaign including design, medicinal chemistry‐driven hit‐to‐lead optimization and in‐depth biological profiling of a new QSI generation is reported. The QSI possess excellent activity in inhibiting pyocyanin production and PqsR reporter‐gene with IC50 values as low as 200 and 11 × 10−9 m, respectively. Drug metabolism and pharmacokinetics (DMPK) as well as safety pharmacology studies especially highlight the promising translational properties of the lead QSI for pulmonary applications. Moreover, target engagement of the lead QSI is shown in a PA mucoid lung infection mouse model. Beyond that, a significant synergistic effect of a QSI‐tobramycin (Tob) combination against PA biofilms using a tailor‐made squalene‐derived nanoparticle (NP) formulation, which enhance the minimum biofilm eradicating concentration (MBEC) of Tob more than 32‐fold is demonstrated. The novel lead QSI and the accompanying NP formulation highlight the potential of adjunctive pathoblocker‐mediated therapy against PA infections opening up avenues for preclinical development.
  • Broad Spectrum Antibiotic Xanthocillin X Effectively Kills Acinetobacter baumannii via Dysregulation of Heme Biosynthesis

    Hübner, Ines; Shapiro, Justin A.; Hoßmann, Jörn; Drechsel, Jonas; Hacker, Stephan M.; Rather, Philip N.; Pieper, Dietmar H.; Wuest, William M.; Sieber, Stephan A.; HZI,Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7,38124 Braunschweig, Germany. (American Chemical Society (ACS), 2021-01-20)
    Isonitrile natural products exhibit promising antibacterial activities. However, their mechanism of action (MoA) remains largely unknown. Based on the nanomolar potency of xanthocillin X (Xan) against diverse difficult-to-treat Gram-negative bacteria, including the critical priority pathogen Acinetobacter baumannii, we performed in-depth studies to decipher its MoA. While neither metal binding nor cellular protein targets were detected as relevant for Xan’s antibiotic effects, sequencing of resistant strains revealed a conserved mutation in the heme biosynthesis enzyme porphobilinogen synthase (PbgS). This mutation caused impaired enzymatic efficiency indicative of reduced heme production. This discovery led to the validation of an untapped mechanism, by which direct heme sequestration of Xan prevents its binding into cognate enzyme pockets resulting in uncontrolled cofactor biosynthesis, accumulation of porphyrins, and corresponding stress with deleterious effects for bacterial viability. Thus, Xan represents a promising antibiotic displaying activity even against multidrug resistant strains, while exhibiting low toxicity to human cells.
  • Eradication of chronic HCV infection: improvement of dysbiosis only in patients without liver cirrhosis.

    Wellhöner, Freya; Döscher, Nico; Woelfl, Franziska; Vital, Marius; Plumeier, Iris; Kahl, Silke; Potthoff, Andrej; Manns, Michael Peter; Pieper, Dietmar Helmut; Cornberg, Markus; et al. (Wiley, 2021-01-07)
    It is well accepted that liver diseases and their outcomes are associated with intestinal microbiota but causality is difficult to establish. The intestinal microbiota is altered in patients with hepatitis C. As chronic HCV infection can now be cured in almost all patients, it is an ideal model to study the influence of liver disease on the microbiota. We aimed to analyze prospectively the changes in the gut microbiome in patients who received direct acting antivirals (DAA) and achieved sustained virological response (SVR). Amplicon sequencing of the V1-V2 region in the 16S rRNA gene was performed in stool samples of patients with chronic hepatitis C. Patients in the treatment group received direct acting antivirals (n=65) whereas in the control group no DAA were given (n=33). Only patients achieving SVR were included. The alpha diversity increased numerical but not significantly from baseline to SVR24/48 (2.784±0.248 vs. 2.846±0.224; p= 0.057). When stratifying for the presence of liver cirrhosis, a significant increase in diversity was only seen in patients without cirrhosis. Differences in the microbial community structure induced by the achievement of SVR were only observed in patients without liver cirrhosis. In patients with liver cirrhosis and in the control group, no significant differences were observed. In conclusion, the achievement of SVR24/48 in patients with chronic HCV was associated with changes in the intestinal microbiota. However, these changes were only seen in patients without liver cirrhosis. A major role of liver remodeling on the intestinal microbiota is indicated by the dynamics of the intestinal microbial community structure depending on the stage of fibrosis in patients resolving chronic hepatitis C.
  • Lethal Neonatal Respiratory Failure by Perinatal Transmission of Ureaplasma Parvum after Maternal PPROM.

    Zöllkau, Janine; Pieper, Dietmar H; Pastuschek, Jana; Makarewicz, Oliwia; Mentzel, Hans-Joachim; Dawczynski, Kristin; Schleußner, Ekkehard; HZI,Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7,38124 Braunschweig, Germany. (Thieme Verlag, 2020-12-18)
    A primiparous pregnant woman was admitted due to preterm premature rupture of membranes (PPROM) at 27+0 week of gestational age (WGA). Conventional vaginal microbiological analysis had no pathological finding. Management decisions based on national guidelines included antenatal corticoids, tocolytics and antibiotics. Unstoppable efforts of preterm labor in 28+0 WGA and supposed amniotic infection syndrome necessitated emergency cesarean section. The preterm infant underwent NICU therapy, developed an early-onset neonatal sepsis and therapy-refractory pulmonary insufficiency with consecutive right heart failure, resulting in death on the 36th day of life. Microbiota analyses by 16Sr DNA sequencing was performed from maternal vaginal swabs and from neonatal pharyngeal swabs. Maternal antibiotic treatment resulted in depletion of physiological vaginal colonization with Lactobacillus crispatus. Ureaplasma parvum became the dominant vaginal microorganism at delivery and was detected in high relative abundance in the neonatal specimen. Progressive radiological air-space changes and interstitial pathologies associated with Ureaplasma infection (bronchopulmonary dysplasia type III) were seen early at the 3rd and distinctly from 14th day of life. This clearly demonstrates the need of vaginal colonization diagnostics in PPROM patients and awareness of the consecutive risks in the preterm. Vaginal microbiome analysis may allow individualized and targeted maternal and fetal diagnostic, prophylactic and therapeutic strategies to identify, protect and treat the high-risk neonates after PPROM.
  • Cohort Profile: The LoewenKIDS Study - life-course perspective on infections, the microbiome and the development of the immune system in early childhood.

    Gottschick, Cornelia; Raupach-Rosin, Heike; Langer, Susan; Hassan, Lamiaa; Horn, Johannes; Dorendorf, Evelyn; Caputo, Mahrrouz; Bittner, Martina; Beier, Lea; Rübsamen, Nicole; et al. (Oxford Academic, 2019-02-27)
    [Noabstract available]
  • Antibacterial activity of xylose-derived LpxC inhibitors - Synthesis, biological evaluation and molecular docking studies.

    Dreger, Alexander; Hoff, Katharina; Agoglitta, Oriana; Hotop, Sven-Kevin; Brönstrup, Mark; Heisig, Peter; Kirchmair, Johannes; Holl, Ralph; HZI,Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7,38124 Braunschweig, Germany. (Elsevier, 2020-12-31)
    LpxC inhibitors represent a promising class of novel antibiotics selectively combating Gram-negative bacteria. In chiral pool syntheses starting from D- and L-xylose, a series of four 2r,3c,4t-configured C-furanosidic LpxC inhibitors was obtained. The synthesized hydroxamic acids were tested for antibacterial and LpxC inhibitory activity, the acquired biological data were compared with those of previously synthesized C-furanosides, and molecular docking studies were performed to rationalize the observed structure-activity relationships. Additionally, bacterial uptake and susceptibility to efflux pump systems were investigated for the most promising stereoisomers.
  • Tailored Cofactor Traps for the Detection of Hemithioacetal-Forming Pyridoxal Kinases.

    Hübner, Ines; Dienemann, Jan-Niklas; Friederich, Julia; Schneider, Sabine; Sieber, Stephan A; HZI,Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7,38124 Braunschweig, Germany. (American Society for Chemistry (ACS), 2020-12-03)
    Pyridoxal kinases (PLK) are crucial enzymes for the biosynthesis of pyridoxal phosphate, an important cofactor in a plethora of enzymatic reactions. The evolution of these enzymes resulted in different catalytic designs. In addition to the active site, the importance of a cysteine, embedded within a distant flexible lid region, was recently demonstrated. This cysteine forms a hemithioacetal with the pyridoxal aldehyde and is essential for catalysis. Despite the prevalence of these enzymes in various organisms, no tools were yet available to study the relevance of this lid residue. Here, we introduce pyridoxal probes, each equipped with an electrophilic trapping group in place of the aldehyde to target PLK reactive lid cysteines as a mimic of hemithioacetal formation. The addition of alkyne handles placed at two different positions within the pyridoxal structure facilitates enrichment of PLKs from living cells. Interestingly, depending on the position, the probes displayed a preference for either Gram-positive or Gram-negative PLK enrichment. By applying the cofactor traps, we were able to validate not only previously investigated Staphylococcus aureus and Enterococcus faecalis PLKs but also Escherichia coli and Pseudomonas aeruginosa PLKs, unravelling a crucial role of the lid cysteine for catalysis. Overall, our tailored probes facilitated a reliable readout of lid cysteine containing PLKs, qualifying them as chemical tools for mining further diverse proteomes for this important enzyme class.
  • Buchwald-Hartwig versus Microwave-Assisted Amination of Chloroquinolines: En Route to the Pyoverdin Chromophore

    Seubert, Philipp; Freund, Marcel; Rudolf, Richard; Lin, Yulin; Altevogt, Luca; Bilitewski, Ursula; Baro, Angelika; Laschat, Sabine; HZI,Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7,38124 Braunschweig, Germany. (Thieme Verlag, 2020-07-22)
    The reaction of 2-chloro-3-nitroquinoline and a series of amines and aminoalkanoates under basic microwave-mediated conditions and Buchwald-Hartwig amination conditions is reported. The microwave irradiation favored the reaction with amines, resulting in yields up to 80%, while amino acid functionalization gave yields comparable to those of BuchwaldHartwig amination. (2R)-4-[(6,7-dimethoxy-3-nitroquinolinyl)amino]-2-hydroxybutanoate could be successfully cyclized to the pyoverdin chromophore, a subunit of siderophores.
  • SAR Studies of the Leupyrrins: Design and Total Synthesis of Highly Potent Simplified Leupylogs.

    Wosniok, Paul R; Knopf, Christopher; Dreisigacker, Sandra; Orozco-Rodriguez, J Manuel; Hinkelmann, Bettina; Mueller, Peter P; Brönstrup, Mark; Menche, Dirk; HZI,Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7,38124 Braunschweig, Germany. (Wiley, 2020-11-11)
    Invited for the cover of this issue is the group of Dirk Menche at the University of Bonn. The image depicts the natural product leupyrrin A1 and a synthetic leupylog in balance on an IC50 weighing scale. Read the full text of the article at 10.1002/chem.202002622.
  • The Peptide Chain Release Factor Methyltransferase PrmC Influences the Pseudomonas aeruginosa PA14 Endo- and Exometabolome.

    Depke, Tobias; Häussler, Susanne; Brönstrup, Mark; HZI,Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7,38124 Braunschweig, Germany. (MDPI, 2020-10-18)
    Pseudomonas aeruginosa is one of the most important nosocomial pathogens and understanding its virulence is the key to effective control of P. aeruginosa infections. The regulatory network governing virulence factor production in P. aeruginosa is exceptionally complex. Previous studies have shown that the peptide chain release factor methyltransferase PrmC plays an important role in bacterial pathogenicity. Yet, the underlying molecular mechanism is incompletely understood. In this study, we used untargeted liquid and gas chromatography coupled to mass spectrometry to characterise the metabolome of a prmC defective P. aeruginosa PA14 strain in comparison with the corresponding strain complemented with prmC in trans. The comprehensive metabolomics data provided new insight into the influence of prmC on virulence and metabolism. prmC deficiency had broad effects on the endo- and exometabolome of P. aeruginosa PA14, with a marked decrease of the levels of aromatic compounds accompanied by reduced precursor supply from the shikimate pathway. Furthermore, a pronounced decrease of phenazine production was observed as well as lower abundance of alkylquinolones. Unexpectedly, the metabolomics data showed no prmC-dependent effect on rhamnolipid production and an increase in pyochelin levels. A putative virulence biomarker identified in a previous study was significantly less abundant in the prmC deficient strain.
  • Non-Invasive Luciferase Imaging of Type I Interferon Induction in a Transgenic Mouse Model of Biomaterial Associated Bacterial Infections: Microbial Specificity and Inter-Bacterial Species Interactions.

    Rahim, Muhammad Imran; Winkel, Andreas; Lienenklaus, Stefan; Stumpp, Nico S; Szafrański, Szymon P; Kommerein, Nadine; Willbold, Elmar; Reifenrath, Janin; Mueller, Peter P; Eisenburger, Michael; et al. (MDPI, 2020-10-21)
    The performance of biomaterials is often compromised by bacterial infections and subsequent inflammation. So far, the conventional analysis of inflammatory processes in vivo involves time-consuming histology and biochemical assays. The present study employed a mouse model where interferon beta (IFN-β) is monitored as a marker for non-invasive rapid detection of inflammation in implant-related infections. The mouse model comprises subcutaneous implantation of morphologically modified titanium, followed by experimental infections with four taxonomically diverse oral bacteria: Streptococcus oralis, Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis and Treponema denticola (as mono culture or selected mixed-culture). IFN-β expression increased upon infections depending on the type of pathogen and was prolonged by the presence of the implant. IFN-β expression kinetics reduced with two mixed species infections when compared with the single species. Histological and confocal microscopy confirmed pathogen-specific infiltration of inflammatory cells at the implant-tissue interface. This was observed mainly in the vicinity of infected implants and was, in contrast to interferon expression, higher in infections with dual species. In summary, this non-invasive mouse model can be used to quantify longitudinally host inflammation in real time and suggests that the polymicrobial character of infection, highly relevant to clinical situations, has complex effects on host immunity.
  • Synthetic studies of cystobactamids as antibiotics and bacterial imaging carriers lead to compounds with high: In vivo efficacy

    Testolin, Giambattista; Cirnski, Katarina; Rox, Katharina; Prochnow, Hans; Fetz, Verena; Grandclaudon, Charlotte; Mollner, Tim; Baiyoumy, Alain; Ritter, Antje; Leitner, Christian; et al. (RSC, 2020-01-01)
    There is an alarming scarcity of novel chemical matter with bioactivity against multidrug-resistant Gram-negative bacterial pathogens. Cystobactamids, recently discovered natural products from myxobacteria, are an exception to this trend. Their unusual chemical structure, composed of oligomeric para-aminobenzoic acid moieties, is associated with a high antibiotic activity through the inhibition of gyrase. In this study, structural determinants of cystobactamid's antibacterial potency were defined at five positions, which were varied using three different synthetic routes to the cystobactamid scaffold. The potency against Acinetobacter baumannii could be increased ten-fold to an MIC (minimum inhibitory concentration) of 0.06 μg mL−1, and the previously identified spectrum gap of Klebsiella pneumoniae could be closed compared to the natural products (MIC of 0.5 μg mL−1). Proteolytic degradation of cystobactamids by the resistance factor AlbD was prevented by an amide-triazole replacement. Conjugation of cystobactamid's N-terminal tetrapeptide to a Bodipy moiety induced the selective localization of the fluorophore for bacterial imaging purposes. Finally, a first in vivo proof of concept was obtained in an E. coli infection mouse model, where derivative 22 led to the reduction of bacterial loads (cfu, colony-forming units) in muscle, lung and kidneys by five orders of magnitude compared to vehicle-treated mice. These findings qualify cystobactamids as highly promising lead structures against infections caused by Gram-positive and Gram-negative bacterial pathogens.
  • Host-induced spermidine production in motile triggers phagocytic uptake.

    Felgner, Sebastian; Preusse, Matthias; Beutling, Ulrike; Stahnke, Stephanie; Pawar, Vinay; Rohde, Manfred; Brönstrup, Mark; Stradal, Theresia; Häussler, Susanne; HZI,Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7,38124 Braunschweig, Germany. (elifeSciences, 2020-09-22)
    Exploring the complexity of host-pathogen communication is vital to understand why microbes persist within a host, while others are cleared. Here, we employed a dual-sequencing approach to unravel conversational turn-taking of dynamic host-pathogen communications. We demonstrate that upon hitting a host cell, motile Pseudomonas aeruginosa induce a specific gene expression program. This results in the expression of spermidine on the surface, which specifically activates the PIP3-pathway to induce phagocytic uptake into primary or immortalized murine cells. Non-motile bacteria are more immunogenic due to a lower expression of arnT upon host-cell contact, but do not produce spermidine and are phagocytosed less. We demonstrate that not only the presence of pathogen inherent molecular patterns induces immune responses, but that bacterial motility is linked to a host-cell-induced expression of additional immune modulators. Our results emphasize on the value of integrating microbiological and immunological findings to unravel complex and dynamic host-pathogen interactions.
  • Toll-like Receptor 5 Activation by the CagY Repeat Domains of Helicobacter pylori.

    Tegtmeyer, Nicole; Neddermann, Matthias; Lind, Judith; Pachathundikandi, Suneesh Kumar; Sharafutdinov, Irshad; Gutiérrez-Escobar, Andrés Julián; Brönstrup, Mark; Tegge, Werner; Hong, Minsun; Rohde, Manfred; et al. (Cell Press, 2020-11-15)
    Helicobacter pylori (Hp) is an important human pathogen associated with gastric inflammation and neoplasia. It is commonly believed that this bacterium avoids major immune recognition by Toll-like receptors (TLRs) because of low intrinsic activity of its flagellin and lipopolysaccharides (LPS). In particular, TLR5 specifically detects flagellins in various bacterial pathogens, while Hp evolved mutations in flagellin to evade detection through TLR5. Cancerogenic Hp strains encode a type IV secretion system (T4SS). The T4SS core component and pilus-associated protein CagY, a large VirB10 ortholog, drives effector molecule translocation. Here, we identify CagY as a flagellin-independent TLR5 agonist. We detect five TLR5 interaction sites, promoting binding of CagY-positive Hp to TLR5-expressing cells, TLR5 stimulation, and intracellular signal transduction. Consequently, CagY constitutes a remarkable VirB10 member detected by TLR5, driving crucial innate immune responses by this human pathogen.
  • Synthesis and Biological Evaluation of a Library of AGE-Related Amino Acid Triazole Crosslinkers

    Icik, Esra; Jolly, Anthony; Löffler, Paul; Agelidis, Nektarios; Bugdayci, Bakiye; Altevogt, Luca; Bilitewski, Ursula; Baro, Angelika; LASCHAT, SABINE; HZI,Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7,38124 Braunschweig, Germany. (Wiley-VCH, 2020-08-10)
    Three N‐Boc‐protected amino acids, l‐serine, l‐aspartic, and l‐glutamic acid, were either converted into their methyl azidoalkanoates or various alkynes via Bestmann‐Ohira strategy or via reaction with propargylamine and propargyl bromide, respectively. The Cu‐catalyzed click reaction provided a library of amino acid based triazoles, which were further N‐methylated to triazolium iodides or deprotected and precipitated as free amino acid triazole dihydrochlorides. The biological properties of all derivatives were investigated by cytotoxicity assay (against L929 mouse fibroblasts) and broth microdilution method (E. coli ΔTolC and S. aureus). First results reveal complete inactivity for triazolium iodides with cell viabilities and microbial growths nearly 100 %, indicating them as possible analogs of advanced glycation endproducts (AGEs).
  • Untargeted LC-MS Metabolomics Differentiates Between Virulent and Avirulent Clinical Strains of Pseudomonas aeruginosa

    Depke, Tobias; Thöming, Janne Gesine; Kordes, Adrian; Häussler, Susanne; Brönstrup, Mark; HZI,Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7,38124 Braunschweig, Germany. (MDPI, 2020-07-13)
    Pseudomonas aeruginosa is a facultative pathogen that can cause, inter alia, acute or chronic pneumonia in predisposed individuals. The gram-negative bacterium displays considerable genomic and phenotypic diversity that is also shaped by small molecule secondary metabolites. The discrimination of virulence phenotypes is highly relevant to the diagnosis and prognosis of P. aeruginosa infections. In order to discover small molecule metabolites that distinguish different virulence phenotypes of P. aeruginosa, 35 clinical strains were cultivated under standard conditions, characterized in terms of virulence and biofilm phenotype, and their metabolomes were investigated by untargeted liquid chromatography-mass spectrometry. The data was both mined for individual candidate markers as well as used to construct statistical models to infer the virulence phenotype from metabolomics data. We found that clinical strains that differed in their virulence and biofilm phenotype also had pronounced divergence in their metabolomes, as underlined by 332 features that were significantly differentially abundant with fold changes greater than 1.5 in both directions. Important virulence-associated secondary metabolites like rhamnolipids, alkyl quinolones or phenazines were found to be strongly upregulated in virulent strains. In contrast, we observed little change in primary metabolism. A hitherto novel cationic metabolite with a sum formula of C12H15N2 could be identified as a candidate biomarker. A random forest model was able to classify strains according to their virulence and biofilm phenotype with an area under the Receiver Operation Characteristics curve of 0.84. These findings demonstrate that untargeted metabolomics is a valuable tool to characterize P. aeruginosa virulence, and to explore interrelations between clinically important phenotypic traits and the bacterial metabolome.
  • Impact of dental cement on the peri-implant biofilm-microbial comparison of two different cements in an in vivo observational study.

    Korsch, Michael; Marten, Silke-Mareike; Walther, Winfried; Vital, Marius; Pieper, Dietmar H; Dötsch, Andreas; HZI,Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7,38124 Braunschweig, Germany. (Wiley, 2018-08-20)
    Background: The type of cement used in cemented fixed implant-supported restorations influences formation of undetected excess cement and composition of the peri-implant biofilm. Excess cement and dysbiosis of the biofilm involve the risk of peri-implant inflammation. Purpose: The aim of the study was to investigate the impact of two different cements on the peri-implant biofilm and inflammation. Materials and methods: In an observational study, the suprastructures of 34 patients with cemented fixed implant-supported restorations were revised. In 20 patients, a methacrylate cement (Premier Implant cement [PIC]) and in 14 patients, a zinc oxide eugenol cement (Temp Bond [TB]) were used. After revision, TB was used for recementation. During revision and follow-up after 1 year, microbial samples were obtained. Results: Excess cement was found in 12 (60%) of the 20 patients with PIC. Suppuration was observed in two (25%) implants with PIC without excess cement (PIC-) and in all 12 (100%) implants with PIC and excess cement (PIC+). Implants cemented with TB had neither excess cement nor suppuration. The taxonomic analysis of the microbial samples revealed an accumulation of periodontal pathogens in the PIC patients independent of the presence of excess cement. Significantly, fewer oral pathogens occurred in patients with TB compared to patients with PIC. TB was used in all cases (PIC and TB) for recementation. In the follow-up check, suppuration was not found around any of the implants with PIC-, only around one implant with PIC+ and around one implant with TB. Bacterial species associated with severe periodontal infections that were abundant in PIC- and PIC+ samples before the revision were reduced after 1 year to levels found in the TB samples. Conclusions: The revision and recementation with TB had a positive effect on the peri-implant biofilm in cases with PIC. The cementation of suprastructures on implants with TB is an alternative method to be considered.
  • Toward Biorecycling: Isolation of a Soil Bacterium That Grows on a Polyurethane Oligomer and Monomer.

    Espinosa, María José Cárdenas; Blanco, Andrea Colina; Schmidgall, Tabea; Atanasoff-Kardjalieff, Anna Katharina; Kappelmeyer, Uwe; Tischler, Dirk; Pieper, Dietmar H; Heipieper, Hermann J; Eberlein, Christian; HZI,Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7,38124 Braunschweig, Germany. (Frontiers, 2020-03-27)
    The fate of plastic waste and a sustainable use of synthetic polymers is one of the major challenges of the twenty first century. Waste valorization strategies can contribute to the solution of this problem. Besides chemical recycling, biological degradation could be a promising tool. Among the high diversity of synthetic polymers, polyurethanes are widely used as foams and insulation materials. In order to examine bacterial biodegradability of polyurethanes, a soil bacterium was isolated from a site rich in brittle plastic waste. The strain, identified as Pseudomonas sp. by 16S rRNA gene sequencing and membrane fatty acid profile, was able to grow on a PU-diol solution, a polyurethane oligomer, as the sole source of carbon and energy. In addition, the strain was able to use 2,4-diaminotoluene, a common precursor and putative degradation intermediate of polyurethanes, respectively, as sole source of energy, carbon, and nitrogen. Whole genome sequencing of the strain revealed the presence of numerus catabolic genes for aromatic compounds. Growth on potential intermediates of 2,4-diaminotoluene degradation, other aromatic growth substrates and a comparison with a protein data base of oxygenases present in the genome, led to the proposal of a degradation pathway.
  • Polyhalonitrobutadienes as Versatile Building Blocks for the Biotargeted Synthesis of Substituted N-Heterocyclic Compounds.

    Zapol'skii, Viktor A; Bilitewski, Ursula; Kupiec, Sören R; Ramming, Isabell; Kaufmann, Dieter E; HZI,Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7,38124 Braunschweig, Germany. (MDPI, 2020-06-21)
    Substituted nitrogen heterocycles are structural key units in many important pharmaceuticals. A new synthetic approach towards heterocyclic compounds displaying antibacterial activity against Staphylococcus aureus or cytotoxic activity has been developed. The selective synthesis of a series of 64 new N-heterocycles from the three nitrobutadienes 2-nitroperchloro-1,3-butadiene, 4-bromotetrachloro-2-nitro-1,3-butadiene and (Z)-1,1,4-trichloro-2,4-dinitrobuta-1,3-diene proved feasible. Their reactions with N-, O- and S-nucleophiles provide rapid access to push-pull substituted benzoxazolines, benzimidazolines, imidazolidines, thiazolidinones, pyrazoles, pyrimidines, pyridopyrimidines, benzoquinolines, isothiazoles, dihydroisoxazoles, and thiophenes with unique substitution patterns. Antibacterial activities of 64 synthesized compounds were examined. Additionally, seven compounds (thiazolidinone, nitropyrimidine, indole, pyridopyrimidine, and thiophene derivatives) exhibited a significant cytotoxicity with IC50-values from 1.05 to 20.1 µM. In conclusion, it was demonstrated that polyhalonitrobutadienes have an interesting potential as structural backbones for a variety of highly functionalized, pharmaceutically active heterocycles.

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