• Deutsch
  • Home
  • Search
  • Browse
  • Publish
  • Help
Schließen

Refine

Has Fulltext

  • yes (20)

Is part of the Bibliography

  • yes (20)

Year of publication

  • 2021 (3)
  • 2020 (2)
  • 2019 (2)
  • 2018 (1)
  • 2017 (3)
  • 2016 (2)
  • 2015 (2)
  • 2013 (1)
  • 2012 (1)
  • 2011 (3)
+ more

Document Type

  • Journal article (20)

Language

  • English (20)

Keywords

  • Staphylococcus aureus (7)
  • antibacterial activity (3)
  • antibiotics (3)
  • epithelial cells (3)
  • synthesis (3)
  • vancomycin (3)
  • cytotoxicity (2)
  • host cells (2)
  • inhibition (2)
  • pathogens (2)
+ more

Author

  • Ohlsen, Knut (20)
  • Hertlein, Tobias (14)
  • Lalk, Michael (4)
  • Hilgeroth, Andreas (3)
  • Jakob, Peter (3)
  • Sturm, Volker (3)
  • Basse-Lüsebrink, Thomas (2)
  • Beijer, Barbro (2)
  • Domhan, Cornelius (2)
  • Donat, Stefanie (2)
+ more

Institute

  • Institut für Molekulare Infektionsbiologie (18)
  • Theodor-Boveri-Institut für Biowissenschaften (3)
  • Physikalisches Institut (2)
  • Botanischer Garten (1)
  • Institut für Humangenetik (1)
  • Institut für Hygiene und Mikrobiologie (1)
  • Institut für Klinische Biochemie und Pathobiochemie (1)
  • Institut für Organische Chemie (1)
  • Institut für Pharmazie und Lebensmittelchemie (1)
  • Lehrstuhl für Tissue Engineering und Regenerative Medizin (1)
+ more

EU-Project number / Contract (GA) number

  • 335568 (1)
  • ERC335568 (1)
  • ESF_14-BM-A55-0005_16 (1)

20 search hits

  • 1 to 10
  • BibTeX
  • CSV
  • RIS
  • XML
  • 10
  • 20
  • 50
  • 100

Sort by

  • Year
  • Year
  • Title
  • Title
  • Author
  • Author
Reproducibility challenges in the search for antibacterial compounds from nature (2021)
Masota, Nelson E. ; Vogg, Gerd ; Ohlsen, Knut ; Holzgrabe, Ulrike
Background Reproducibility of reported antibacterial activities of plant extracts has long remained questionable. Although plant-related factors should be well considered in serious pharmacognostic research, they are often not addressed in many research papers. Here we highlight the challenges in reproducing antibacterial activities of plant extracts. Methods Plants with reported antibacterial activities of interest were obtained from a literature review. Antibacterial activities against Escherichia coli and Klebsiella pneumoniae were tested using extracts’ solutions in 10% DMSO and acetone. Compositions of working solutions from both solvents were established using LC-MS analysis. Moreover, the availability of details likely to affect reproducibility was evaluated in articles which reported antibacterial activities of studied plants. Results Inhibition of bacterial growth at MIC of 256–1024 μg/mL was observed in only 15.4% of identical plant species. These values were 4–16-fold higher than those reported earlier. Further, 18.2% of related plant species had MICs of 128–256 μg/mL. Besides, 29.2% and 95.8% of the extracts were soluble to sparingly soluble in 10% DMSO and acetone, respectively. Extracts’ solutions in both solvents showed similar qualitative compositions, with differing quantities of corresponding phytochemicals. Details regarding seasons and growth state at collection were missing in 65% and 95% of evaluated articles, respectively. Likewise, solvents used to dissolve the extracts were lacking in 30% of the articles, whereas 40% of them used unidentified bacterial isolates. Conclusion Reproducibility of previously reported activities from plants’ extracts is a multi-factorial aspect. Thus, collective approaches are necessary in addressing the highlighted challenges.
Intracellular Staphylococcus aureus employs the cysteine protease staphopain A to induce host cell death in epithelial cells (2021)
Stelzner, Kathrin ; Boyny, Aziza ; Hertlein, Tobias ; Sroka, Aneta ; Moldovan, Adriana ; Paprotka, Kerstin ; Kessie, David ; Mehling, Helene ; Potempa, Jan ; Ohlsen, Knut ; Fraunholz, Martin J. ; Rudel, Thomas
Staphylococcus aureus is a major human pathogen, which can invade and survive in non-professional and professional phagocytes. Uptake by host cells is thought to contribute to pathogenicity and persistence of the bacterium. Upon internalization by epithelial cells, cytotoxic S. aureus strains can escape from the phagosome, replicate in the cytosol and induce host cell death. Here, we identified a staphylococcal cysteine protease to induce cell death after translocation of intracellular S. aureus into the host cell cytoplasm. We demonstrated that loss of staphopain A function leads to delayed onset of host cell death and prolonged intracellular replication of S. aureus in epithelial cells. Overexpression of staphopain A in a non-cytotoxic strain facilitated intracellular killing of the host cell even in the absence of detectable intracellular replication. Moreover, staphopain A contributed to efficient colonization of the lung in a mouse pneumonia model. In phagocytic cells, where intracellular S. aureus is exclusively localized in the phagosome, staphopain A did not contribute to cytotoxicity. Our study suggests that staphopain A is utilized by S. aureus to exit the epithelial host cell and thus contributes to tissue destruction and dissemination of infection. Author summary Staphylococcus aureus is an antibiotic-resistant pathogen that emerges in hospital and community settings and can cause a variety of diseases ranging from skin abscesses to lung inflammation and blood poisoning. The bacterium can asymptomatically colonize the upper respiratory tract and skin of humans and take advantage of opportune conditions, like immunodeficiency or breached barriers, to cause infection. Although S. aureus was not regarded as intracellular bacterium, it can be internalized by human cells and subsequently exit the host cells by induction of cell death, which is considered to cause tissue destruction and spread of infection. The bacterial virulence factors and underlying molecular mechanisms involved in the intracellular lifestyle of S. aureus remain largely unknown. We identified a bacterial cysteine protease to contribute to host cell death of epithelial cells mediated by intracellular S. aureus. Staphopain A induced killing of the host cell after translocation of the pathogen into the cell cytosol, while bacterial proliferation was not required. Further, the protease enhanced survival of the pathogen during lung infection. These findings reveal a novel, intracellular role for the bacterial protease staphopain A.
Staphylococcus aureus Exploits a Non-ribosomal Cyclic Dipeptide to Modulate Survival within Epithelial Cells and Phagocytes (2016)
Blättner, Sebastian ; Das, Sudip ; Paprotka, Kerstin ; Eilers, Ursula ; Krischke, Markus ; Kretschmer, Dorothee ; Remmele, Christian W. ; Dittrich, Marcus ; Müller, Tobias ; Schuelein-Voelk, Christina ; Hertlein, Tobias ; Mueller, Martin J. ; Huettel, Bruno ; Reinhardt, Richard ; Ohlsen, Knut ; Rudel, Thomas ; Fraunholz, Martin J.
Community-acquired (CA) Staphylococcus aureus cause various diseases even in healthy individuals. Enhanced virulence of CA-strains is partly attributed to increased production of toxins such as phenol-soluble modulins (PSM). The pathogen is internalized efficiently by mammalian host cells and intracellular S. aureus has recently been shown to contribute to disease. Upon internalization, cytotoxic S. aureus strains can disrupt phagosomal membranes and kill host cells in a PSM-dependent manner. However, PSM are not sufficient for these processes. Here we screened for factors required for intracellular S. aureus virulence. We infected escape reporter host cells with strains from an established transposon mutant library and detected phagosomal escape rates using automated microscopy. We thereby, among other factors, identified a non-ribosomal peptide synthetase (NRPS) to be required for efficient phagosomal escape and intracellular survival of S. aureus as well as induction of host cell death. By genetic complementation as well as supplementation with the synthetic NRPS product, the cyclic dipeptide phevalin, wild-type phenotypes were restored. We further demonstrate that the NRPS is contributing to virulence in a mouse pneumonia model. Together, our data illustrate a hitherto unrecognized function of the S. aureus NRPS and its dipeptide product during S. aureus infection.
Vancomycin-lipopeptide conjugates with high antimicrobial activity on vancomycin-resistant enterococci (2020)
Mühlberg, Eric ; Umstätter, Florian ; Domhan, Cornelius ; Hertlein, Tobias ; Ohlsen, Knut ; Krause, Andreas ; Kleist, Christian ; Beijer, Barbro ; Zimmermann, Stefan ; Haberkorn, Uwe ; Mier, Walter ; Uhl, Philipp
Multidrug-resistant bacteria represent one of the most important health care problems worldwide. While there are numerous drugs available for standard therapy, there are only a few compounds capable of serving as a last resort for severe infections. Therefore, approaches to control multidrug-resistant bacteria must be implemented. Here, a strategy of reactivating the established glycopeptide antibiotic vancomycin by structural modification with polycationic peptides and subsequent fatty acid conjugation to overcome the resistance of multidrug-resistant bacteria was followed. This study especially focuses on the structure–activity relationship, depending on the modification site and fatty acid chain length. The synthesized conjugates showed high antimicrobial potential on vancomycin-resistant enterococci. We were able to demonstrate that the antimicrobial activity of the vancomycin-lipopeptide conjugates depends on the chain length of the attached fatty acid. All conjugates showed good cytocompatibility in vitro and in vivo. Radiolabeling enabled the in vivo determination of pharmacokinetics in Wistar rats by molecular imaging and biodistribution studies. An improved biodistribution profile in comparison to unmodified vancomycin was observed. While vancomycin is rapidly excreted by the kidneys, the most potent conjugate shows a hepatobiliary excretion profile. In conclusion, these results demonstrate the potential of the structural modification of already established antibiotics to provide highly active compounds for tackling multidrug-resistant bacteria.
Novel small-molecule antibacterials against Gram-positive pathogens of Staphylococcus and Enterococcus species (2019)
Seethaler, Marius ; Hertlein, Tobias ; Wecklein, Björn ; Ymeraj, Alba ; Ohlsen, Knut ; Lalk, Michael ; Hilgeroth, Andreas
Defeat of the antibiotic resistance of pathogenic bacteria is one great challenge today and for the future. In the last century many classes of effective antibacterials have been developed, so that upcoming resistances could be met with novel drugs of various compound classes. Meanwhile, there is a certain lack of research of the pharmaceutical companies, and thus there are missing developments of novel antibiotics. Gram-positive bacteria are the most important cause of clinical infections. The number of novel antibacterials in clinical trials is strongly restricted. There is an urgent need to find novel antibacterials. We used synthetic chemistry to build completely novel hybrid molecules of substituted indoles and benzothiophene. In a simple one-pot reaction, two novel types of thienocarbazoles were yielded. Both indole substituted compound classes have been evaluated as completely novel antibacterials against the Staphylococcus and Enterococcus species. The evaluated partly promising activities depend on the indole substituent type. First lead compounds have been evaluated within in vivo studies. They confirmed the in vitro results for the new classes of small-molecule antibacterials.
Induced pluripotent stem cell-derived brain endothelial cells as a cellular model to study Neisseria meningitidis infection (2019)
Gomes, Sara F. Martins ; Westermann, Alexander J. ; Sauerwein, Till ; Hertlein, Tobias ; Förstner, Konrad U. ; Ohlsen, Knut ; Metzger, Marco ; Shusta, Eric V. ; Kim, Brandon J. ; Appelt-Menzel, Antje ; Schubert-Unkmeir, Alexandra
Meningococcal meningitis is a severe central nervous system infection that occurs when Neisseria meningitidis (Nm) penetrates brain endothelial cells (BECs) of the meningeal blood-cerebrospinal fluid barrier. As a human-specific pathogen, in vivo models are greatly limited and pose a significant challenge. In vitro cell models have been developed, however, most lack critical BEC phenotypes limiting their usefulness. Human BECs generated from induced pluripotent stem cells (iPSCs) retain BEC properties and offer the prospect of modeling the human-specific Nm interaction with BECs. Here, we exploit iPSC-BECs as a novel cellular model to study Nm host-pathogen interactions, and provide an overview of host responses to Nm infection. Using iPSC-BECs, we first confirmed that multiple Nm strains and mutants follow similar phenotypes to previously described models. The recruitment of the recently published pilus adhesin receptor CD147 underneath meningococcal microcolonies could be verified in iPSC-BECs. Nm was also observed to significantly increase the expression of pro-inflammatory and neutrophil-specific chemokines IL6, CXCL1, CXCL2, CXCL8, and CCL20, and the secretion of IFN-γ and RANTES. For the first time, we directly observe that Nm disrupts the three tight junction proteins ZO-1, Occludin, and Claudin-5, which become frayed and/or discontinuous in BECs upon Nm challenge. In accordance with tight junction loss, a sharp loss in trans-endothelial electrical resistance, and an increase in sodium fluorescein permeability and in bacterial transmigration, was observed. Finally, we established RNA-Seq of sorted, infected iPSC-BECs, providing expression data of Nm-responsive host genes. Altogether, this model provides novel insights into Nm pathogenesis, including an impact of Nm on barrier properties and tight junction complexes, and suggests that the paracellular route may contribute to Nm traversal of BECs.
Modeling antibiotic and cytotoxic effects of the dimeric isoquinoline IQ-143 on metabolism and its regulation in Staphylococcus aureus, Staphylococcus epidermidis and human cells (2011)
Cecil, Alexander ; Rikanovic, Carina ; Ohlsen, Knut ; Liang, Chunguang ; Bernhardt, Jorg ; Oelschlaeger, Tobias A. ; Gulder, Tanja ; Bringmann, Gerd ; Holzgrabe, Ulrike ; Unger, Matthias ; Dandekar, Thomas
Background: Xenobiotics represent an environmental stress and as such are a source for antibiotics, including the isoquinoline (IQ) compound IQ-143. Here, we demonstrate the utility of complementary analysis of both host and pathogen datasets in assessing bacterial adaptation to IQ-143, a synthetic analog of the novel type N,C-coupled naphthyl-isoquinoline alkaloid ancisheynine. Results: Metabolite measurements, gene expression data and functional assays were combined with metabolic modeling to assess the effects of IQ-143 on Staphylococcus aureus, Staphylococcus epidermidis and human cell lines, as a potential paradigm for novel antibiotics. Genome annotation and PCR validation identified novel enzymes in the primary metabolism of staphylococci. Gene expression response analysis and metabolic modeling demonstrated the adaptation of enzymes to IQ-143, including those not affected by significant gene expression changes. At lower concentrations, IQ-143 was bacteriostatic, and at higher concentrations bactericidal, while the analysis suggested that the mode of action was a direct interference in nucleotide and energy metabolism. Experiments in human cell lines supported the conclusions from pathway modeling and found that IQ-143 had low cytotoxicity. Conclusions: The data suggest that IQ-143 is a promising lead compound for antibiotic therapy against staphylococci. The combination of gene expression and metabolite analyses with in silico modeling of metabolite pathways allowed us to study metabolic adaptations in detail and can be used for the evaluation of metabolic effects of other xenobiotics.
The vSa\(\alpha\) Specific Lipoprotein Like Cluster (lpl) of S. aureus USA300 Contributes to Immune Stimulation and Invasion in Human Cells (2015)
Nguyen, Minh Thu ; Kraft, Beatrice ; Yu, Wenqi ; Demicrioglu, Dogan Doruk ; Hertlein, Tobias ; Burian, Marc ; Schmaler, Mathias ; Boller, Klaus ; Bekeredjian-Ding, Isabelle ; Ohlsen, Knut ; Schittek, Birgit ; Götz, Friedrich
All Staphylococcus aureus genomes contain a genomic island, which is termed vSa\(\alpha\) and characterized by two clusters of tandem repeat sequences, i.e. the exotoxin (set) and 'lipoprotein-like' genes (lpl). Based on their structural similarities the vSa\(\alpha\) islands have been classified as type I to IV. The genomes of highly pathogenic and particularly epidemic S. aureus strains (USA300, N315, Mu50, NCTC8325, Newman, COL, JH1 or JH9) belonging to the clonal complexes CC5 and CC8 bear a type I vSa\(\alpha\) island. Since the contribution of the lpl gene cluster encoded in the vSa\(\alpha\) island to virulence is unclear to date, we deleted the entire lpl gene cluster in S. aureus USA300. The results showed that the mutant was deficient in the stimulation of pro-inflammatory cytokines in human monocytes, macrophages and keratinocytes. Purified lipoprotein Lpl1 was further shown to elicit a TLR2-dependent response. Furthermore, heterologous expression of the USA300 lpl cluster in other S. aureus strains enhanced their immune stimulatory activity. Most importantly, the lpl cluster contributed to invasion of S. aureus into human keratinocytes and mouse skin and the non-invasive S. carnosus expressing the lpl gene cluster became invasive. Additionally, in a murine kidney abscess model the bacterial burden in the kidneys was higher in wild type than in mutant mice. In this infection model the lpl cluster, thus, contributes to virulence. The present report is one of the first studies addressing the role of the vSa\(\alpha\) encoded lpl gene cluster in staphylococcal virulence. The finding that the lpl gene cluster contributes to internalization into non-professional antigen presenting cells such as keratinocytes high-lights the lpl as a new cell surface component that triggers host cell invasion by S. aureus. Increased invasion in murine skin and an increased bacterial burden in a murine kidney abscess model suggest that the lpl gene cluster serves as an important virulence factor.
The effect of skin fatty acids on Staphylococcus aureus (2015)
Neumann, Yvonne ; Ohlsen, Knut ; Donat, Stefanie ; Engelmann, Susanne ; Kusch, Harald ; Albrecht, Dirk ; Cartron, Michael ; Hurd, Alexander ; Foster, Simon J.
Staphylococcus aureus is a commensal of the human nose and skin. Human skin fatty acids, in particular cis-6-hexadecenoic acid (C-6-H), have high antistaphylococcal activity and can inhibit virulence determinant production. Here, we show that sub-MIC levels of C-6-H result in induction of increased resistance. The mechanism(s) of C-6-H activity was investigated by combined transcriptome and proteome analyses. Proteome analysis demonstrated a pleiotropic effect of C-6-H on virulence determinant production. In response to C-6-H, transcriptomics revealed altered expression of over 500 genes, involved in many aspects of virulence and cellular physiology. The expression of toxins (hla, hlb, hlgBC) was reduced, whereas that of host defence evasion components (cap, sspAB, katA) was increased. In particular, members of the SaeRS regulon had highly reduced expression, and the use of specific mutants revealed that the effect on toxin production is likely mediated via SaeRS
\(^{19}\)F Magnetic Resonance Imaging of Perfluorocarbons for the Evaluation of Response to Antibiotic Therapy in a Staphylococcus aureus Infection Model (2013)
Hertlein, Tobias ; Sturm, Volker ; Jakob, Peter ; Ohlsen, Knut
Background The emergence of antibiotic resistant bacteria in recent decades has highlighted the importance of developing new drugs to treat infections. However, in addition to the design of new drugs, the development of accurate preclinical testing methods is essential. In vivo imaging technologies such as bioluminescence imaging (BLI) or magnetic resonance imaging (MRI) are promising approaches. In a previous study, we showed the effectiveness of \(^{19}\)F MRI using perfluorocarbon (PFC) emulsions for detecting the site of Staphylococcus aureus infection. In the present follow-up study, we investigated the use of this method for in vivo visualization of the effects of antibiotic therapy. Methods/Principal findings Mice were infected with S. aureus Xen29 and treated with 0.9% NaCl solution, vancomycin or linezolid. Mock treatment led to the highest bioluminescence values during infection followed by vancomycin treatment. Counting the number of colony-forming units (cfu) at 7 days post-infection (p.i.) showed the highest bacterial burden for the mock group and the lowest for the linezolid group. Administration of PFCs at day 2 p.i. led to the accumulation of \(^{19}\)F at the rim of the abscess in all mice (in the shape of a hollow sphere), and antibiotic treatment decreased the \(^{19}\)F signal intensity and volume. Linezolid showed the strongest effect. The BLI, cfu, and MRI results were comparable. Conclusions \(^{19}\)F-MRI with PFCs is an effective non-invasive method for assessing the effects of antibiotic therapy in vivo. This method does not depend on pathogen specific markers and can therefore be used to estimate the efficacy of antibacterial therapy against a broad range of clinically relevant pathogens, and to localize sites of infection.
  • 1 to 10

DINI-Zertifikat     OPUS4 Logo

  • Contact
  • |
  • Imprint
  • |
  • Sitemap