Novel antimicrobial combinations for treatment against pathogens associated with infected diabetic foot ulcers

Abstract

Many promising conventional antimicrobial agents have low permeability and restricted biodistribution, their encapsulation into efficient drug delivery carriers is crucial to increasing their bioavailability and retention time. Lipodisq® (LQ) nanoparticles consist of a circular phospholipid bilayer that is stabilized by an annulus of polystyrene-co-maleic anhydride (PSMA). PSMA is used extensively in structural biology to extract lipids and stabilize integral membrane proteins for biophysical studies. Also, the use of enzymes has been shown to degrade extracellular polymeric matrices which can improve the penetration and efficacy of antimicrobials to eradicate biofilm. Biofilm extracellular polymeric matrix components (eDNA, protein and polysaccharides) play a key role in the impermeability of conventional antimicrobial agents in the biofilm. Treatment of biofilm-related infections with conventional antimicrobial agents usually results in prolonged treatment or failure due to their impermeability and restricted biodistribution within the biofilm extracellular polymeric matrices. Therefore, there is an urgent and crucial need for alternative therapeutic approaches that can enhance the penetration, and biodistribution (availability and retention) for easy inactivation of the biofilm viable cells. In this study, the enhanced susceptibility effect of the novel LQ-loaded antimicrobial nanoparticles was investigated against planktonic cells and further determine the potentiality for the eradication of biofilm viable cells using the ISO 14729 stand-alone test procedure. The susceptibility and time-kill assays of the novel LQ-loaded antimicrobial formulations (chlorhexidine-LQ (CHLX-LQ), polymyxin B-LQ, polymyxin E-LQ, linezolid-LQ and poly-ε-lysine-LQ) showed improved antimicrobial activity against test organisms. On the other hand, the free LQ nanoparticle without antimicrobial had no effect on viable cells. Novel polymyxin B and E-loaded LQ have a significant antimicrobial effect against S. aureus and C. albicans planktonic cells with low MIC/MBC values. The novel CHLX-LQ showed enhanced inactivation of S. aureus and C. albicans biofilm viable cells. Incorporation of DNase 1, lysozyme and proteinase K to octenidine, alexidine, and chlorhexidine-LQ against C. albicans and S. aureus biofilm significantly enhanced the inactivation of biofilm viable cells. This study, therefore, suggests that octenidine and alexidine have the potential as dispersal agents in S. aureus biofilm. Additionally, suggest that LQ have the potential to act as a delivery vehicle for antimicrobials to enhance penetration and effect in biofilms. And the combination of LQ-loaded antimicrobials and enzymes can further improve the therapeutic approach to treating biofilm-related infections.