group leader: Dr. Abraham

Recent Submissions

  • Unsaturated Fatty Acids Control Biofilm Formation of Staphylococcus aureus and Other Gram-Positive Bacteria.

    Yuyama, Kamila Tomoko; Rohde, Manfred; Molinari, Gabriella; Stadler, Marc; Abraham, Wolf-Rainer (2020-11-08)
    Infections involving biofilms are difficult to treat due to increased resistances against antibiotics and the immune system. Hence, there is an urgent demand for novel drugs against biofilm infections. During our search for novel biofilm inhibitors from fungi, we isolated linoleic acid from the ascomycete Hypoxylon fragiforme which showed biofilm inhibition of several bacteria at sub-MIC concentrations. Many fatty acids possess antimicrobial activities, but their minimum inhibitory concentrations (MIC) are high and reports on biofilm interferences are scarce. We demonstrated that not only linoleic acid but several unsaturated long-chain fatty acids inhibited biofilms at sub-MIC concentrations. The antibiofilm activity exerted by long-chain fatty acids was mainly against Gram-positive bacteria, especially against Staphylococcus aureus. Micrographs of treated S. aureus biofilms revealed a reduction in the extracellular polymeric substances, pointing to a possible mode of action of fatty acids on S. aureus biofilms. The fatty acids had a strong species specificity. Poly-unsaturated fatty acids had higher activities than saturated ones, but no obvious rule could be found for the optimal length and desaturation for maximal activity. As free fatty acids are non-toxic and ubiquitous in food, they may offer a novel tool, especially in combination with antibiotics, for the control of biofilm infections.
  • Chitosan nanoparticles potentiate the in vitro and in vivo effects of curcumin and other natural compounds.

    Lopes, Vanessa Falchetti; Giongo, Camila Nascimento; de Almeida Campos, Laís; Abraham, Wolf-Rainer; Mainardes, Rubiana Mara; Khalil, Najeh Maissar; HZI,Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7,38124 Braunschweig, Germany. (Bentham Science Publishers, 2020-11-24)
    The development of biodegradable nanoparticles is an important tool for the biological transport of chemical compounds. The nanoencapsulation reduces the biopharmaceutical and pharmacokinetic drawbacks of compounds and enhances their biological properties. Naturally occurring polymers such as proteins and polysaccharides have been widely applied in the development of nanostructured systems of several therapeutic agents. Among them is chitosan, a crustacean-carapace-chitin derived biopolymer. In addition to its biocompatibility and biodegradability, chitosan is known for its mucoadhesion properties. Chitosan-based nanostructured systems potentiate most of aspects of the loaded drugs, including cellular transport and other biological effects. The use of chitosan nanoparticles enhances permeation, stability and bioactivity of natural compounds. In this review, an overview of the main features of chitosan nanoparticles that improved in vitro and in vivo effects of bioactive natural molecules is given, emphasizing the results obtained with curcumin.
  • Nanoparticles as A Tool for Broadening Antifungal Activities.

    Renzi, Daniele Fernanda; de Almeida Campos, Laís; Miranda, Eduardo Hösel; Mainardes, Rubiana Mara; Abraham, Wolf-Rainer; Grigoletto, Diana Fortkamp; Khalil, Najeh Maissar; HZI,Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7,38124 Braunschweig, Germany. (Bentham Science Publisher, 2020-03-30)
    The Fungal infections are diseases that are considered neglected although their infection rates have increased worldwide in the last decades. Thus, since the antifungal arsenal is restricted and many strains have shown resistance new therapeutic alternatives are necessary. Nanoparticles are considered important alternatives to promote drug delivery. In this sense, the objective of the present study was to evaluate the contributions of newly developed nanoparticles to the treatment of fungal infections. Studies have shown that nanoparticles generally improve the biopharmaceutical and pharmacokinetic characteristics of antifungals, which is reflected in a greater pharmacodynamic potential and lower toxicity, as well as the possibility of prolonged action. It also offers the proposition of new routes of administration. Nanotechnology is known to contribute to a new drug delivery system, not only for the control of infectious diseases, but for various other diseases as well. In recent years, several studies have emphasized its application in infectious diseases, presenting better alternatives for the treatment of fungal infections.
  • Secondary metabolites produced by endophytic fungi: novel antifungal activity of fumiquinone B

    Grigoletto, Diana Fortkamp; Correia, Ana Maria Lima; Abraham, Wolf-Rainer; Rodrigues, Andre; Assis, Marco Antonio; Ferreira, Antonio Gilberto; Massaroli, Michelli; Lira, Simone Possedente de; HZI,Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7,38124 Braunschweig, Germany. (Universidade Estadual de Maringa, 2019-12-18)
    Fungi are present in the most diverse environments including the interior of plant tissues, living as endophytes without causing apparent damage. These endophytes are producers of secondary metabolites, also known as natural products, such as fungicides. Here, we evaluated the ethyl acetate fractions obtained from endophytic fungi isolated from plants in the genus Begonia. The fractions were submitted to inhibitory test against the plant pathogens Diaporthe phaseolorum and Colletotrichum gloeosporioides. From the 88 ethyl acetate fractions evaluated, 14.7 % inhibited C. gloeosporioides and 11.3 % inhibited D. phaseolorum. One fungal isolate displaying an active fraction was selected for chemical investigation. The fungus identified as Neopestalotiopsis sp., produced a compound that was active against D. phaseolorum, with a MIC of 312 µg mL-1 (1,695.3 µM). The compound was identified by mass spectrometry and 1H NMR as the known compound fumiquinone B. The results highlight that the endophytes are capable of producing compounds that may be used to control plant pathogens. The compound fumiquinone B is reported for the first time as an antifungal agent against D. phaseolorum, a relevant plant pathogen worldwide. This is also the first report of the production of fumiquinone B by the genus Neopestalotiopsis.
  • Establishment of an induced memory response in Pseudomonas aeruginosa during infection of a eukaryotic host.

    Kordes, Adrian; Grahl, Nora; Koska, Michal; Preusse, Matthias; Arce-Rodriguez, Alejandro; Abraham, Wolf-Rainer; Kaever, Volkhard; Häussler, Susanne; HZI,Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7,38124 Braunschweig, Germany. (Springer-Nature, 2019-08-01)
    In a given habitat, bacterial cells often experience recurrent exposures to the same environmental stimulus. The ability to memorize the past event and to adjust current behaviors can lead to efficient adaptation to the recurring stimulus. Here we demonstrate that the versatile bacterium Pseudomonas aeruginosa adopts a virulence phenotype after serial passage in the invertebrate model host Galleria mellonella. The virulence phenotype was not linked to the acquisition of genetic variations and was sustained for several generations, despite cultivation of the ex vivo virulence-adapted P. aeruginosa cells under rich medium conditions in vitro. Transcriptional reprogramming seemed to be induced by a host-specific food source, as reprogramming was also observed upon cultivation of P. aeruginosa in rich medium supplemented with polyunsaturated long-chain fatty acids. The establishment of induced memory responses adds a time dimension and seems to fill the gap between long-term evolutionary genotypic adaptation and short-term induced individual responses. Efforts to unravel the fundamental mechanisms that underlie the carry-over effect to induce such memory responses will continue to be of importance as hysteretic behavior can serve survival of bacterial populations in changing and challenging habitats.
  • Cytochalasans Act as Inhibitors of Biofilm Formation of Staphylococcus Aureus.

    Yuyama, Kamila Tomoko; Wendt, Lucile; Surup, Frank; Kretz, Robin; Chepkirui, Clara; Wittstein, Kathrin; Boonlarppradab, Chollaratt; Wongkanoun, Sarunyou; Luangsa-Ard, Jennifer; Stadler, Marc; et al. (MPDI, 2018-10-30)
    During the course of our ongoing work to discover new inhibitors of biofilm formation of Staphylococcus aureus from fungal sources, we observed biofilm inhibition by cytochalasans isolated from cultures of the ascomycete Hypoxylon fragiforme for the first time. Two new compounds were purified by a bioassay-guided fractionation procedure; their structures were elucidated subsequently by nuclear magnetic resonance (NMR) spectroscopy and high-resolution mass spectrometry (HR-MS). This unexpected finding prompted us to test further cytochalasans from other fungi and from commercial sources for comparison. Out of 21 cytochalasans, 13 showed significant inhibition of Staphylococcus aureus biofilm formation at subtoxic levels. These findings indicate the potential of cytochalasans as biofilm inhibitors for the first time, also because the minimum inhibitory concentrations (MIC) are independent of the anti-biofilm activities. However, cytochalasans are known to be inhibitors of actin, making some of them very toxic for eukaryotic cells. Since the chemical structures of the tested compounds were rather diverse, the inclusion of additional derivatives, as well as the evaluation of their selectivity against mammalian cells vs. the bacterium, will be necessary as next step in order to develop structure-activity relationships and identify the optimal candidates for development of an anti-biofilm agent. View Full-Text
  • De Novo Fatty Acid Synthesis During Mycobacterial Infection Is a Prerequisite for the Function of Highly Proliferative T Cells, But Not for Dendritic Cells or Macrophages.

    Stüve, Philipp; Minarrieta, Lucía; Erdmann, Hanna; Arnold-Schrauf, Catharina; Swallow, Maxine; Guderian, Melanie; Krull, Freyja; Hölscher, Alexandra; Ghorbani, Peyman; Behrends, Jochen; et al. (Frontiers, 2018-01-01)
    Mycobacterium tuberculosis (Mtb), the causative agent of human tuberculosis, is able to efficiently manipulate the host immune system establishing chronic infection, yet the underlying mechanisms of immune evasion are not fully understood. Evidence suggests that this pathogen interferes with host cell lipid metabolism to ensure its persistence. Fatty acid metabolism is regulated by acetyl-CoA carboxylase (ACC) 1 and 2; both isoforms catalyze the conversion of acetyl-CoA into malonyl-CoA, but have distinct roles. ACC1 is located in the cytosol, where it regulates de novo fatty acid synthesis (FAS), while ACC2 is associated with the outer mitochondrial membrane, regulating fatty acid oxidation (FAO). In macrophages, mycobacteria induce metabolic changes that lead to the cytosolic accumulation of lipids. This reprogramming impairs macrophage activation and contributes to chronic infection. In dendritic cells (DCs), FAS has been suggested to underlie optimal cytokine production and antigen presentation, but little is known about the metabolic changes occurring in DCs upon mycobacterial infection and how they affect the outcome of the immune response. We therefore determined the role of fatty acid metabolism in myeloid cells and T cells during Mycobacterium bovis BCG or Mtb infection, using novel genetic mouse models that allow cell-specific deletion of ACC1 and ACC2 in DCs, macrophages, or T cells. Our results demonstrate that de novo FAS is induced in DCs and macrophages upon M. bovis BCG infection. However, ACC1 expression in DCs and macrophages is not required to control mycobacteria. Similarly, absence of ACC2 did not influence the ability of DCs and macrophages to cope with infection. Furthermore, deletion of ACC1 in DCs or macrophages had no effect on systemic pro-inflammatory cytokine production or T cell priming, suggesting that FAS is dispensable for an intact innate response against mycobacteria. In contrast, mice with a deletion of ACC1 specifically in T cells fail to generate efficient T helper 1 responses and succumb early to Mtb infection. In summary, our results reveal ACC1-dependent FAS as a crucial mechanism in T cells, but not DCs or macrophages, to fight against mycobacterial infection.
  • Bioactive Compounds Produced by Hypoxylon fragiforme against Staphylococcus aureus Biofilms.

    Yuyama, Kamila Tomoko; Chepkirui, Clara; Wendt, Lucile; Fortkamp, Diana; Stadler, Marc; Abraham, Wolf-Rainer; Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7, 38124 Braunschweig, Germany. (2017-12-12)
    Treating infections organized in biofilms is a challenge due to the resistance of the pathogens against antibiotics and host immune cells. Many fungi grow in a wet environment, favorable for the growth of bacterial biofilms, and we speculated that fungi possess some strategies to control these bacterial biofilms. A fungus identified as Hypoxylon fragiforme, was collected in the Harz Mountains, Germany, and its mycelial culture was fermented in different culture media for 67 days to test its biological potential against bacterial biofilms. Sclerin, sclerin diacid and its 3-methyl monoester (methyl 1-(5-hydroxy-6-carboxylic-2,3,4-trimethylphenyl) propionate) are here described for the first time from this fungus. Sclerin and its diacid interfered with the biofilm formation of the pathogen Staphylococcus aureus, inhibiting 86% and 80% of the biofilm at 256 μg mL-1, respectively, but not killing the bacterium. Interestingly, the monomethylester of sclerin diacid was inactive. Although these compounds did not possess any activity against a pre-formed biofilm, they prevented its formation at subtoxic concentrations. Furthermore, sclerin and its diacid displayed a high specificity against Staphylococcus aureus, indicating a good strategy against pathogenic biofilms when combined with antibiotics.
  • Fumitremorgins and Relatives - from Tremorgenic Compounds to Valuable Anti-Cancer Drugs.

    Abraham, Wolf-Rainer; Hemholtz Centre for infection research, Inhoffenstr.7, 38124 Braunschweig, Germany. (2017-07-24)
    Fumitremorgins are mycotoxins but can also inhibit cancer cells and reverse their drug resistance.
  • Arvoredol: An unusual chlorinated and biofilm inhibiting polyketide from a marine Penicillium sp. of the Brazilian coast

    Scopel, Marina; Mothes, Beatriz; Lerner, Clea B.; Henriques, Am?lia T.; Macedo, Alexandre J.; Abraham, Wolf-Rainer; Helmholtz Centre for infection research, Inhoffenstr. 7., 38124 Braunschweig, Germany. (2017-06)
    Penicillium sp. F37 has been isolated from the marine sponge Axinella corrugata and shown to be closely related to Penicillium maximae. From the culture of Penicillium sp. F37 arvoredol, a novel chlorinated polyketide with 6,7-dihydro-4(5H)-benzofuranone moiety has been isolated and characterized by spectroscopic methods Arvoredol prevented biofilm formation of the human pathogen Staphylococcus epidermidis at a concentration of 125 μg mL−1 by 40%. It was also active against colorectal carcinoma HCT116 cells with a MIC of 7.9 μg mL−1. © 2017 Phytochemical Society of Europe
  • Combining Biofilm-Controlling Compounds and Antibiotics as a Promising New Way to Control Biofilm Infections.

    Estrela, Andréia Bergamo; Abraham, Wolf-Rainer; Helmholtz Centre for infection research, Inhoffenstr. 7, 38124 Braunschweig, Germany. (2010-05-11)
    Many bacteria grow on surfaces forming biofilms. In this structure, they are well protected and often high dosages of antibiotics cannot clear infectious biofilms. The formation and stabilization of biofilms are mediated by diffusible autoinducers (e.g. N-acyl homoserine lactones, small peptides, furanosyl borate diester). Metabolites interfering with this process have been identified in plants, animals and microbes, and synthetic analogues are known. Additionally, this seems to be not the only way to control biofilms. Enzymes capable of cleaving essential components of the biofilm matrix, e.g. polysaccharides or extracellular DNA, and thus weakening the biofilm architecture have been identified. Bacteria also have mechanisms to dissolve their biofilms and return to planktonic lifestyle. Only a few compounds responsible for the signalling of these processes are known, but they may open a completely novel line of biofilm control. All these approaches lead to the destruction of the biofilm but not the killing of the pathogens. Therefore, a combination of biofilm-destroying compounds and antibiotics to handle biofilm infections is proposed. In this article, different approaches to combine biofilm-controlling compounds and antibiotics to fight biofilm infections are discussed, as well as the balance between biofilm formation and virulence.
  • Fungal Metabolites for the Control of Biofilm Infections

    Estrela, Andréia; Abraham, Wolf-Rainer; Helmholtz Centre for infection research, Inhoffenstr. 7, 38124 Braunschweig, Germany. (2016-08-12)
  • Coprinuslactone protects the edible mushroom Coprinus comatus against biofilm infections by blocking both quorum-sensing and MurA.

    de Carvalho, Maira P; Gulotta, Giuseppe; do Amaral, Matheus W; Lünsdorf, Heinrich; Sasse, Florenz; Abraham, Wolf-Rainer; Helmholtz Centre for infection research, Inhoffenstr. 7, 38124 Braunschweig, Germany. (2016-10-03)
    Pathogens embedded in biofilms are involved in many infections and are very difficult to treat with antibiotics because of higher resistance compared to planktonic cells. Therefore, new approaches for their control are urgently needed. One way to search for biofilm dispersing compounds is to look at defense strategies of organisms exposed to wet environments, which makes them prone to biofilm infections. It is reasonable to assume that mushrooms have developed mechanisms to control biofilms on their sporocarps (fruiting bodies). A preliminary screening for biofilms on sporocarps revealed several species with few or no bacteria on their sporocarps. From the edible mushroom Coprinus comatus where no bacteria on the sporocarp could be detected (3R,4S)-2-methylene-3,4-dihydroxypentanoic acid 1,4-lactone, named coprinuslactone, was isolated. Coprinuslactone interfered with quorum-sensing and dispersed biofilms of Pseudomonas aeruginosa, where it also reduced the formation of the pathogenicity factors pyocyanin and rhamnolipid B. Coprinuslactone also damaged Staphylococcus aureus cells in biofilms at subtoxic concentrations. Furthermore, it inhibited UDP-N-acetylglucosamine enolpyruvyl transferase (MurA), essential for bacterial cell wall synthesis. These two modes of action ensure the inhibition of a broad spectrum of pathogens on the fruiting body but may also be useful for future clinical applications. This article is protected by copyright. All rights reserved.
  • Diversity and Activity of Bacterial Biofilm Communities Growing on Hexachlorocyclohexane

    Gebreil, Ahmed Shawky; Abraham, Wolf-Rainer; Helmholtz Centre for infection research, Inhoffenstr. 7, 38124 Braunschweig, Germany. (2016-08-03)
  • cis-2-Alkenoic acids as promising drugs for the control of biofilm infections.

    Yuyama, Kamila Tomoko; Abraham, Wolf-Rainer; Helmholtz Centre for infection research, Inhoffenstr. 7, 38124 Braunschweig, Germany. (2016-05-06)
    Microbes attached to surfaces and form biofilms where they are difficult to eradicate. Here they are embedded in a complex matrix of polymers and are much less sensitive against antibiotics or the immune system.
  • Going beyond the Control of Quorum-Sensing to Combat Biofilm Infections.

    Abraham, Wolf-Rainer; Helmholtz Centre for infection research, Inhoffenstr. 7, 38124 Braunschweig, Germany. (2016)
    Most bacteria attach to surfaces where they form a biofilm, cells embedded in a complex matrix of polymers. Cells in biofilms are much better protected against noxious agents than free-living cells. As a consequence it is very difficult to control pathogens with antibiotics in biofilm infections and novel targets are urgently needed. One approach aims at the communication between cells to form and to maintain a biofilm, a process called quorum-sensing. Water soluble small-sized molecules mediate this process and a number of antagonists of these compounds have been found. In this review natural compounds and synthetic drugs which do not interfere with the classical quorum-sensing compounds are discussed. For some of these compounds the targets are still not known, but others interfere with the formation of exopolysaccharides, virulence factors, or cell wall synthesis or they start an internal program of biofilm dispersal. Some of their targets are more conserved among pathogens than the receptors for quorum sensing autoinducers mediating quorum-sensing, enabling a broader application of the drug. The broad spectrum of mechanisms, the diversity of bioactive compounds, their activity against several targets, and the conservation of some targets among bacterial pathogens are promising aspects for several clinical applications of this type of biofilm-controlling compound in the future.
  • Secondary Metabolites Control the Associated Bacterial Communities of Saprophytic Basidiomycotina Fungi.

    de Carvalho, Maira Peres; Türck, Patrick; Abraham, Wolf-Rainer; Helmholtz Centre for infection research (HZI), Inhoffenstraße 7, 38124 Braunschweig, Germany. (2015)
    Fungi grow under humid conditions and are, therefore, prone to biofilm infections. A 16S rRNA fingerprint analysis was performed on 49 sporocarps of Basidiomycotina in order to determine whether they are able to control these biofilms. Ninety-five bacterial phylotypes, comprising 4 phyla and 10 families, were identified. While ectomycorrhizal fungi harbored the highest bacterial diversity, saprophytic fungi showed little or no association with bacteria. Seven fungal species were screened for antimicrobial and antibiofilm activities. Biofilm formation and bacterial growth was inhibited by extracts obtained from saprophytic fungi, which confirmed the hypothesis that many fungi modulate biofilm colonization on their sporocarps.
  • Release of Periplasmic Nucleotidase Induced by Human Antimicrobial Peptide in E. coli Causes Accumulation of the Immunomodulator Adenosine.

    Estrela, Andreia Bergamo; Türck, Patrick; Stutz, Elaine; Abraham, Wolf-Rainer; Helmholtz Centre for infection research, Inhoffenstr. 7, 38124 Braunschweig, Germany. (2015)
    Previous work by our group described that human β-defensin-2 induces accumulation of extracellular adenosine (Ado) in E. coli cultures through a non-lytic mechanism causing severe plasmolysis. Here, we investigate the presence of AMP as a direct precursor and the involvement of a bacterial enzyme in the generation of extracellular Ado by treated bacteria. Following hBD-2 treatment, metabolites were quantified in the supernatants using targeted HPLC-MS/MS analysis. Microbial growth was monitored by optical density and cell viability was determined by colony forming units counts. Phosphatase activity was measured using chromogenic substrate pNPP. The results demonstrate that defensin-treated E. coli strain W releases AMP in the extracellular space, where it is converted to Ado by a bacterial soluble factor. An increase in phosphatase activity in the supernatant was observed after peptide treatment, similar to the effect of sucrose-induced osmotic stress, suggesting that the periplasmic 5'nucleotidase (5'-NT) is released following the plasmolysis event triggered by the peptide. Ado accumulation was enhanced in the presence of Co2+ ion and inhibited by EDTA, further supporting the involvement of a metallo-phosphatase such as 5'-NT in extracellular AMP conversion into Ado. The comparative analysis of hBD-induced Ado accumulation in different E. coli strains and in Pseudomonas aeruginosa revealed that the response is not correlated to the peptide's effect on cell viability, but indicates it might be dependent on the subcellular distribution of the nucleotidase. Taken together, these data shed light on a yet undescribed mechanism of host-microbial interaction: a human antimicrobial peptide inducing selective release of a bacterial enzyme (E. coli 5'-NT), leading to the formation of a potent immunomodulator metabolite (Ado).
  • A rapid method for breath analysis in cystic fibrosis patients.

    Kramer, R; Sauer-Heilborn, A; Welte, T; Guzman, C A; Höfle, M G; Abraham, Wolf-Rainer; Helmholtz Centre for Infection Research, Inhoffenstraße 7, 38124 Braunschweig, Germany. (2015-04)
    For easy handling and speed of lung diseases diagnostics, approaches based on volatile organic compounds (VOCs), including those emitted by pathogenic microorganisms, are considered but currently require considerable sampling efforts. We tested whether easy-to-handle and fast detection of lung infections is possible using solid-phase microextraction (SPME) of 100 ml of exhaled breath. An analytical procedure for the detection of VOCs from the headspace of epithelial lung cells infected with four human pathogens was developed. The feasibility of this method was tested in a cystic fibrosis (CF) outpatient clinic in vivo. Exhaled breath was extracted by SPME and analyzed by gas chromatography-mass spectrometry (GC-MS). The compositions of VOCs released in the infection model were characteristic for all individual pathogens tested. Exhaled breath of CF patients allowed clear distinction of CF patients and controls by their VOC compositions using multivariate analyses. Interestingly, the major specific VOCs detected in the exhaled breath of infected CF patients in vivo differed from those monitored during bacterial in vitro growth. SPME extraction of VOCs from 100 ml of human breath allowed the distinction between CF patients and healthy probands. Our results highlight the importance of assessing the entire pattern of VOCs instead of selected biomarkers for diagnostic purposes, as well as the need to use clinical samples to identify reliable biomarkers. This study provides the proof-of-concept for the approach using the composition of exhaled VOCs in human breath for the rapid identification of infectious agents in patients with lower respiratory tract infections.

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