[In vitro antimicrobial activity of defensins from rabbit neutrophils against Pseudomonas aeruginosa and its multiple-drug-resistance strains].

OBJECTIVE: To investigate the role and mechanism of defensins from rabbit neutrophils against the multi-drug-resistant (MDR) strains of Pseudomonas aeruginosa. METHODS: Defensins were extracted from rabbit peritoneal neutrophil granules with citric acid and purified by acid urea polyacrylamide gel electrophoresis (AU-PAGE). An agrose gel radial diffusion assay for bactericidal activity in vitro was used and ultrastructural changes of the killed Pseudomonas aeruginosa were examined by use of transmission electron microscope. RESULTS: NP2 was isolated and purified successfully by AU-PAGE. NP2 demonstrated concentration-dependent killing of Pseudomonas aeruginosa and its MDR strain. When the two kinds of Pseudomonas aeruginosa cells exposed to NP2 were examined by transmission electron microscope, we found that the cell membrane was incomplete, the components of cells condensed into pyknotic bodies accompanied by vacuolization, and there was some transudate between the cells. CONCLUSION: Defensin from the rabbit neutrophils exerts potent bactericidal activity against the MDR strain of Pseudomonas aeruginosa. The findings under electron microscope suggest the theory that defensins are capable of destabilizing the cell membrane permeability and causing the death of microorganism.