title: Effects of SecDF on the antimicrobial functions of cathelicidins against Staphylococcus aureus.
abstract: Antimicrobial peptides (AMPs) represent an important part of the innate host immune system. Although they are active against a broad range of pathogens, bacteria have evolved different resistance mechanisms to avoid killing by AMPs. Since not much is known about the impact of efflux pumps on the susceptibility of Gram-positive bacteria to AMPs, especially to the cathelicidins, the aim of this study was to analyze whether Staphylococcus aureus can use efflux pumps to resist the antimicrobial effects of cathelicidins derived from different animal species (human, mouse, rabbit or cattle). For this purpose the minimal inhibitory concentrations (MICs) of S. aureus field isolates for the cathelicidins LL-37, mCRAMP, CAP18, BMAP-27 and BMAP-28 in the presence and absence of different efflux pump inhibitors were determined. Furthermore, the MICs of mutants lacking SecDF, a member of the RND efflux pump family, were determined and compared to the MICs of their respective wildtype and complemented strains. The data demonstrated that after blocking RND-type efflux pumps with 1-(1-naphthylmethyl)-piperazine, the MICs for CAP18, but not those for the other cathelicidins tested, were significantly decreased. In good correlation with these data, significantly decreased MICs for CAP18 and also BMAP-27 have been observed for SecDF knockout mutants as compared to their isogenic wildtype strains. In addition, the MIC values increased again after re-introducing a cloned secDF via plasmid complementation. These results indicated an involvement of SecDF in a reduced efficacy of species-specific cathelicidins against S. aureus.
authors.affiliation: Department of Physiological Chemistry, University of Veterinary Medicine, Hannover, Germany; Institute of Farm Animal Genetics, Friedrich-Loeffler-Institut, Neustadt-Mariensee, Germany.
authors.forename: Stefanie
authors.initials: S
authors.lastname: Blodkamp
authors.affiliation: Institute of Farm Animal Genetics, Friedrich-Loeffler-Institut, Neustadt-Mariensee, Germany.
authors.forename: Kristina
authors.initials: K
authors.lastname: Kadlec
authors.affiliation: Research group Biophysics, Research Centre Borstel, Borstel, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Gutsmann
authors.affiliation: Institute of Medical Microbiology, University of Zurich, Zurich, Switzerland.
authors.forename: Chantal
authors.initials: C
authors.lastname: Quiblier
authors.affiliation: Department of Physiological Chemistry, University of Veterinary Medicine, Hannover, Germany.
authors.forename: Hassan Y
authors.initials: HY
authors.lastname: Naim
authors.affiliation: Institute of Farm Animal Genetics, Friedrich-Loeffler-Institut, Neustadt-Mariensee, Germany. Electronic address: stefan.schwarz@fli.bund.de.
authors.forename: Stefan
authors.initials: S
authors.lastname: Schwarz
authors.affiliation: Department of Physiological Chemistry, University of Veterinary Medicine, Hannover, Germany; Research Centre for Emerging Infections and Zoonoses (RIZ), University of Veterinary Medicine, Hannover, Germany. Electronic address: mkoeckbl@tiho-hannover.de.
authors.forename: Maren
authors.initials: M
authors.lastname: von Köckritz-Blickwede
mesh_terms: D000818:Animals; D000890:Anti-Infective Agents / Q000494:pharmacology*; D023181:Antimicrobial Cationic Peptides / Q000494:pharmacology; D001426:Bacterial Proteins / Q000378:metabolism*; D054804:Cathelicidins / Q000494:pharmacology*; D002417:Cattle; D004198:Disease Susceptibility; D004791:Enzyme Inhibitors; D006801:Humans; D008565:Membrane Proteins / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000378:metabolism*; D055624:Methicillin-Resistant Staphylococcus aureus / Q000187:drug effects / Q000235:genetics; D051379:Mice; D008826:Microbial Sensitivity Tests; D010879:Piperazines / Q000494:pharmacology; D011506:Proteins / Q000494:pharmacology; D011817:Rabbits; D013203:Staphylococcal Infections / Q000188:drug therapy / Q000382:microbiology / Q000662:veterinary*
chemical_list: C511391:1-(1-naphthylmethyl)piperazine; D000890:Anti-Infective Agents; D023181:Antimicrobial Cationic Peptides; C102359:BMAP-27; C102360:BMAP-28; D001426:Bacterial Proteins; D054804:Cathelicidins; D004791:Enzyme Inhibitors; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D010879:Piperazines; D011506:Proteins; C075767:secD protein, Bacteria; C075768:secF protein, Bacteria
keywords: Antimicrobial peptides; Efflux pump inhibitors; Minimal inhibitory concentration (MIC); RND efflux pumps