Holger A G Mueller

Publications of Holger A G Mueller

• Antibacterial activity of human defensins on anaerobic intestinal bacterial species: a major role of HBD-3.

  Authors: Sabine Nuding, Lutz T Zabel, Corinne Enders, Edith Porter, Klaus Fellermann, Jan Wehkamp, Holger A G Mueller, Eduard F Stange

  Microbes and infection / Institut Pasteur. 02/2009;

  Defensins are natural mucosal antimicrobial peptides and their broad spectrum activity against aerobic or facultative anaerobic bacteria has been well investigated. The aim of this study was toDefensins are natural mucosal antimicrobial peptides and their broad spectrum activity against aerobic or facultative anaerobic bacteria has been well investigated. The aim of this study was to systematically examine the antibacterial activity of the small intestinal Paneth cell-derived a-defensin HD5 and the major colonic beta-defensins HBD-1 - 3 against strict anaerobic intestinal bacteria. The antibacterial activity was assessed with a flow cytometric assay employing a membrane potential sensitive dye as marker for loss of cell viability. The majority of the tested strains belonging to the dominant anaerobe genera of the gut, Bacteroides and Parabacteroides, were only minimally affected by the constitutively expressed defensins HD5 and HBD1. The inducible defensin HBD-2 had a limited antibacterial effect, whereas the inducible HBD-3 exhibited potent activity against most strains. The effect of HBD-3 on Bacteroides sp. appeared to be dependent on the presence of oxygen. Bacteroides fragilis strains isolated from blood during bacteraemia or from extraintestinal infections were more resistant to HBD-3 than strains from the physiological gut flora. Thus, defensin resistance is not only species but also strain specific and may be clinically relevant in the host-bacterial interaction influencing mucosal translocation and systemic infection.

• A flow cytometric assay to monitor antimicrobial activity of defensins and cationic tissue extracts.

  Authors: Sabine Nuding, Klaus Fellermann, Jan Wehkamp, Holger A G Mueller, Eduard F Stange

  Journal of microbiological methods. 05/2006; 65(2):335-45.

  To determine the antibacterial activity of defensins and other antimicrobial peptides in biopsy extracts, we evaluated a flow cytometric method with the membrane potential sensitive dyeTo determine the antibacterial activity of defensins and other antimicrobial peptides in biopsy extracts, we evaluated a flow cytometric method with the membrane potential sensitive dye bis-(1,3-dibutylbarbituric acid) trimethine oxonol [DiBAC4(3)]. This assay enables us to discriminate intact non-fluorescent and depolarized fluorescent bacteria after exposure to antimicrobial peptides by measurement at the direct target, the cytoplasmic membrane and the membrane potential. The feasibility of the flow cytometric assay was evaluated with recombinant human beta-defensin 3 (HBD-3) against 25 bacterial strains representing 12 species. HBD-3 showed a broad-spectrum dose dependent activity and the minimal dose to cause depolarization ranged from 1.25 to >15 microg/ml HBD-3, depending on the species tested. The antibacterial effect was diminished with sodium chloride or dithiothreitol and could be abrogated with a HBD-3 antibody. Additionally, isolated cationic extracts from human intestinal biopsies showed a strong bactericidal effect against Escherichia coli K12, E. coli ATCC 25922 and Staphylococcus aureus ATCC 25923, which was diminished towards E. coli at 150 mM NaCl, whereas the activity towards S. aureus ATCC 25923 remained unaffected at physiological salt concentrations. DTT blocked the bactericidal effect of biopsy extracts completely.

• A flow cytometric assay to monitor antimicrobial activity of defensins and cationic tissue extracts

  Authors: Sabine Nuding, Klaus Fellermann, Jan Wehkamp, Holger A.G. Mueller, Eduard F. Stange

  Journal of Microbiological Methods.

  To determine the antibacterial activity of defensins and other antimicrobial peptides in biopsy extracts, we evaluated a flow cytometric method with the membrane potential sensitive dyeTo determine the antibacterial activity of defensins and other antimicrobial peptides in biopsy extracts, we evaluated a flow cytometric method with the membrane potential sensitive dye bis-(1,3-dibutylbarbituric acid) trimethine oxonol [DiBAC4(3)]. This assay enables us to discriminate intact non-fluorescent and depolarized fluorescent bacteria after exposure to antimicrobial peptides by measurement at the direct target, the cytoplasmic membrane and the membrane potential. The feasibility of the flow cytometric assay was evaluated with recombinant human β-defensin 3 (HBD-3) against 25 bacterial strains representing 12 species. HBD-3 showed a broad-spectrum dose dependent activity and the minimal dose to cause depolarization ranged from 1.25 to > 15 μg/ml HBD-3, depending on the species tested. The antibacterial effect was diminished with sodium chloride or dithiothreitol and could be abrogated with a HBD-3 antibody. Additionally, isolated cationic extracts from human intestinal biopsies showed a strong bactericidal effect against Escherichia coli K12, E. coli ATCC 25922 and Staphylococcus aureus ATCC 25923, which was diminished towards E. coli at 150 mM NaCl, whereas the activity towards S. aureus ATCC 25923 remained unaffected at physiological salt concentrations. DTT blocked the bactericidal effect of biopsy extracts completely.

• Antibacterial activity of human defensins on anaerobic intestinal bacterial species: a major role of HBD-3

  Authors: Sabine Nuding, Lutz T. Zabel, Corinne Enders, Edith Porter, Klaus Fellermann, Jan Wehkamp, Holger A.G. Mueller, Eduard F. Stange

  Microbes and Infection.

  Defensins are natural mucosal antimicrobial peptides and their broad spectrum activity against aerobic or facultative anaerobic bacteria has been well investigated. The aim of this study was toDefensins are natural mucosal antimicrobial peptides and their broad spectrum activity against aerobic or facultative anaerobic bacteria has been well investigated. The aim of this study was to systematically examine the antibacterial activity of the small intestinal Paneth cell derived α-defensin HD5 and the major colonic β-defensins HBD-1–3 against strict anaerobic intestinal bacteria. The antibacterial activity was assessed with a flow cytometric assay employing a membrane potential sensitive dye as marker for loss of cell viability. The majority of the tested strains belonging to the dominant anaerobe genera of the gut, Bacteroides and Parabacteroides, were only minimally affected by the constitutively expressed defensins HD5 and HBD-1. The inducible defensin HBD-2 had a limited antibacterial effect, whereas the inducible HBD-3 exhibited potent activity against most strains. The effect of HBD-3 on Bacteroides sp. appeared to be dependent on the presence of oxygen. Bacteroides fragilis strains isolated from blood during bacteremia or from extraintestinal infections were more resistant to HBD-3 than strains from the physiological gut flora. Thus, defensin resistance is not only species- but also strain-specific and may be clinically relevant in the host–bacteria interaction influencing mucosal translocation and systemic infection.