title: Induced resistance to the antimicrobial peptide lactoferricin B in Staphylococcus aureus.
abstract: This study was designed to investigate inducible intrinsic resistance against lactoferricin B in Staphylococcus aureus. Serial passage of seven S. aureus strains in medium with increasing concentrations of peptide resulted in an induced resistance at various levels in all strains. The induced resistance was unstable and decreased relatively rapidly during passages in peptide free medium but the minimum inhibitory concentration remained elevated after thirty passages. Cross-resistance to penicillin G and low-level cross-resistance to the antimicrobial peptides indolicidin and Ala(8,13,18)-magainin-II amide [corrected] was observed. No cross-resistance was observed to the human cathelicidin LL-37. In conclusion, this study shows that S. aureus has intrinsic resistance mechanisms against antimicrobial peptides that can be induced upon exposure, and that this may confer low-level cross-resistance to other antimicrobial peptides.
authors.affiliation: Department of Medical Microbiology, University Hospital of North Norway, P.O. Box 56, N-9038 Tromsø, Norway. orjan.samuelsen@unn.no
authors.forename: Orjan
authors.initials: O
authors.lastname: Samuelsen
authors.forename: Hanne H
authors.initials: HH
authors.lastname: Haukland
authors.forename: Håvard
authors.initials: H
authors.lastname: Jenssen
authors.forename: Manuela
authors.initials: M
authors.lastname: Krämer
authors.forename: Kjersti
authors.initials: K
authors.lastname: Sandvik
authors.forename: Hilde
authors.initials: H
authors.lastname: Ulvatne
authors.forename: Lars H
authors.initials: LH
authors.lastname: Vorland
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D023181:Antimicrobial Cationic Peptides / Q000494:pharmacology; D004352:Drug Resistance, Microbial; D007781:Lactoferrin / Q000494:pharmacology*; D008826:Microbial Sensitivity Tests; D010400:Penicillin G / Q000494:pharmacology; D013211:Staphylococcus aureus / Q000187:drug effects* / Q000502:physiology / Q000648:ultrastructure
chemical_list: D000900:Anti-Bacterial Agents; D023181:Antimicrobial Cationic Peptides; C073143:indolicidin; C082171:lactoferricin B; D007781:Lactoferrin; D010400:Penicillin G