Preparation, characterization and efficacy of lysostaphin-chitosan gel against Staphylococcus aureus

Lysostaphin (LST) is a bacteriocin that cleaves within the pentaglycine cross bridge of Staphylococcus aureus peptidoglycan. Previous studies have reported the high efficiency of LST even against multi drug resistant S. aureus including methicillin resistant S. aureus (MRSA). In this study, we have developed a new chitosan based hydrogel formulation of LST to exploit its anti-staphylococcal activity. The atomic interactions of LST with chitosan were studied by molecular docking studies. The rheology and the antibacterial properties of the developed LSTC gel were evaluated. The developed LST containing chitosan hydrogel (LSTC gel) was flexible, flows smoothly and remains stable at physiological temperature. The in vitro studies by agar well diffusion and ex vivo studies in porcine skin model exhibited a reduction in S. aureus survival by ∼3 Log₁₀CFU/mL in the presence of LSTC gel. The cytocompatibility of the gel was tested in vitro using macrophage RAW 264.7 cell line and in vivo in Drosophila melanogaster. A gradual disruption of S. aureus biofilms with the increase of LST concentrations in the LSTC gel was observed which was confirmed by SEM analysis. We conclude that LSTC gel could be highly effectual and advantageous over antibiotics in treating staphylococcal-topical and biofilm infections.