In vitro bactericidal activity of human β-defensin 2 against nosocomial strains

Human beta-defensin 2 (hBD-2) is a 41-amino acid cationic peptide of the innate immune system that serves as antimicrobial molecule. We determined the bactericidal activity of synthetic hBD-2 against nosocomial strains belonging to eight different bacterial species and exhibiting various antimicrobial resistance phenotypes. The native disulfide connectivity was found essential for the bactericidal activity of hBD-2, while sodium chloride concentration was reversely associated with its potency. hBD-2 exhibited high bactericidal activity against Acinetobacter baumannii, Pseudomonas aeruginosa, Enterococcus faecalis, Enterococcus faecium and Staphylococcus aureus clinical strains. Characteristically, A. baumannii strains that exhibited multi-drug resistant (MDR) phenotypes were susceptible to lower concentrations of hBD-2 (vLD(90) = 3.25-4.5 mu g/ml) in comparison with non-MDR (wild-type) A. baumannii strains (vLD(90) = 3.90-9.35 mu g/ml). Bactericidal activity of hBD-2 was less pronounced against Escherichia coli, Klebsiella pneumoniae and Proteus mirabilis strains but was significantly enhanced against strains of these species that exhibited resistance to several beta-lactam antibiotics. These observations give indications that the natural hBD-2 has a potential therapeutic role against bacterial pathogens and particularly against those exhibiting MDR phenotypes. (C) 2010 Elsevier Inc. All rights reserved.