Deciphering the inhibitory mechanism of antimicrobial peptide pexiganan conjugated with sodium-alginate chitosan-cholesterol nanoparticle against the opportunistic pathogen Acinetobacter baumannii

Abstract

The emergence of antibiotic resistance is one of the most challenging problems of modern times as the armory of conventional antibiotics is quickly exhausting due to the rapid rise of resistance in pathogenic microorganisms. Acinetobacter baumannii, a potential member of ESKAPE group of bacteria, has a great deal of clinical importance causing severe nosocomial infections which often become life-threatening. According to the World Health Organization (WHO), antimicrobial resistance accounts for 2-3 million deaths every year across the world. Since the pathogen has the remarkable ability to acquire or upregulate various resistant determinants in the form of secreting of β-lactamase, aminoglycoside modifying enzymes, uplifting the function of efflux pumps or altering the target sites of different antibiotics; conventional antibiotic therapy often falls short to eradicate the infection. As a possible solution, the application of alternative therapy is therefore the need of the hour. Here we emphasize potentiating the antimicrobial efficacy of pexiganan, a well-known antimicrobial peptide against Gram-negative bacteria. Conjugation with nanoparticles composed of sodium-alginate and chitosan-cholesterol has increased the antimicrobial effect of the peptide on this opportunist pathogen. The evaluation of the bactericidal analysis and minimum inhibitory concentration indicates this nanocomposite can kill the bacteria at a very low concentration (3 μg/ml). When applied to the bacterial biofilm, the key factor for producing recalcitrant infection; our synthesized complex could effectively reduce the biomass in a dose-dependent manner. Later we enfold the mechanism of killing by measuring oxidative stress, cell membrane perforation by biochemical analysis. Our analysis indicates this unique nanocomposite can bypass the need of antibiotic treatment by its pore-forming ability on bacterial membrane. The nominal in-vivo toxicity and non-specific mode of action make it an interesting candidate for future therapeutics.