Lucilin is a 36 residue cecropin antimicrobial peptide identified as a partial genetic sequence in Lucilia sericata maggots. The antimicrobial spectrum and toxicity profile of Lucilin is unknown. We first report the expression of Lucilin as an active recombinant fusion protein with a cysteine protease domain (CPD) tag. The fusion protein, GWLK-Lucilin-CPD-His8, showed maximum overexpression in Escherichia coli BL21 cells after 12 h induction with 0.5 mM IPTG (isopropyl beta-D-thiogalactoside) and growth conditions were 37 degrees C and 150 rpm shaking. The fusion protein was expressed as a soluble form and was purified by Ni-IMAC. The purified protein was active against E. coli ATCC 35218 with a MIC of 0.68 uM, and a clinical isolate of E. coli with extended spectrum beta-lactamase (ESBL) with a MIC of 0.8 mu M. The recombinant GWLK-Lucilin-CPD-His8 was not toxic against human erythrocytes or Vero cells with a therapeutic index > 63. The results suggest that GWLK-Lucilin-CPD-His8 represents a potential candidate for therapy against multidrug resistant Gram-negative bacteria. (C) 2014 Elsevier Inc. All rights reserved.