Discovery of A Novel Membrane-Disruption Peptide against Multi-Drug Resistant Gram-Positive Strains Isolated from Cystic Fibrosis Patients

The prevalence of the infection by multi-drug resistant gram-positive strains, especially methicillin-resistant Staphylococcus aureus (MRSA), is increasing in the airways of cystic fibrosis (CF) patients. The survival of CF patients with the presence of the associated infections was even worse. Although antibiotic therapies have been employed to treat the infections, the environment of CF respiratory tract increases the biofilm-forming ability, which makes bacteria intrinsically resistant to be eradicated. Antimicrobial peptide (AMP) is a promising candidate against drug-resistant bacteria as well as the biofilm. In this study, we reported a novel antimicrobial peptide identified from the skin secretion of Limnonectes fujianensis by the combination of cDNA cloning and MS/MS sequencing, namely Japonicin-2LF. The peptide possesses an a-helical segment and a typical heptapeptide loop, rana box, at the C-terminus. The solid peptide synthesis was performed using Tribute® synthesizer (Protein Technologies), and the synthetic replicates exhibit potent antimicrobial activity against both widetyped and CF clinic-isolated gram-positive strains. The fluorescent staining reveals that Japonicin-2LF efficiently permeabilise the cell membrane of bacteria, leading to cell death. In addition, Japonicin-2LF can inhibit the formation of MRSA biofilm and eradicate it in vitro. To further investigate the antimicrobial effect of Japonicin-2LF in vivo, the acute infection module induced by CF isolated MRSA was employed, using larva of the wax moth, Galleria mellonella. The results demonstrated that 25 mg/kg of Japonicin-2LF increase the survival rate of MRSA infected larva significantly, without producing any toxicity. The study suggests that Japonicin-2LF is such potential molecule that can be developed as a new antibiotic agent for treatment of MRSA associated chronic infection in CF respiratory tract.