title: Bactericidal potency and mechanistic specificity of neutrophil defensins against bovine mastitis pathogens.
abstract: Two neutrophil defensins, rabbit peptides NP-1 and NP-5, were examined for their in vitro antibacterial activity against a panel of Gram-positive and Gram-negative organisms isolated from mastitic cows. Incubation for 60 minutes with 5 micrograms/ml of NP-1 in 10 mM sodium phosphate buffer resulted in substantial killing (greater than 95%) of all organisms tested. Although NP-5 was virtually inactive under these same conditions, supplementation of the incubation mixture with dilute nutrient media sensitized otherwise resistant organisms to this defensin. For both NP-1 and NP-5, bactericidal activity was dependent on time and concentration. Our findings demonstrate that the spectrum of defensin bactericidal activities include clinically important bovine pathogens. Further, the data demonstrate that NP-1 and NP-5, peptides which are homologous in 18 of their 33 residue positions, possess distinct mechanisms of action.
authors.affiliation: Department of Clinical Pathology, School of Veterinary Medicine, University of California, Davis 95616.
authors.forename: J S
authors.initials: JS
authors.lastname: Cullor
authors.forename: S
authors.initials: S
authors.lastname: Wood
authors.forename: W
authors.initials: W
authors.lastname: Smith
authors.forename: L
authors.initials: L
authors.lastname: Panico
authors.forename: M E
authors.initials: ME
authors.lastname: Selsted
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001419:Bacteria / Q000276:immunology*; D001770:Blood Bactericidal Activity; D001798:Blood Proteins / Q000737:chemistry / Q000276:immunology*; D002417:Cattle; D023082:Defensins; D004926:Escherichia coli / Q000276:immunology; D008089:Listeria monocytogenes / Q000276:immunology; D008414:Mastitis, Bovine / Q000382:microbiology*; D008969:Molecular Sequence Data; D009504:Neutrophils / Q000276:immunology*; D011817:Rabbits; D012486:Salmonella typhimurium / Q000276:immunology; D013211:Staphylococcus aureus / Q000276:immunology; D023083:beta-Defensins
chemical_list: D001798:Blood Proteins; D023082:Defensins; D023083:beta-Defensins; C406410:bovine neutrophil beta-defensin 12