Fusogenic Liposomes Increase the Antimicrobial Activity of Vancomycin Against Staphylococcus aureus Biofilm

Abstract

Objective: The aim of the present study was to encapsulate vancomycin in different liposomal formulations and compare the in vitro antimicrobial activity against Staphylococcus aureus biofilms. Methods: Large unilamellar vesicles of conventional (LUV VAN), fusogenic (LUVfuso VAN), and cationic (LUVcat VAN) liposomes encapsulating VAN were characterized in terms of size, polydispersity index, zeta potential, morphology, encapsulation efficiency (%EE) and in vitro release kinetics. The formulations were tested for their Minimum Inhibitory Concentration (MIC) and inhibitory activity on biofilm formation and viability, using methicillin-susceptible S. aureus ATCC 29213 and methicillin-resistant S. aureus ATCC 43300 strains. Key Findings: LUV VAN showed better %EE (32.5%) and sustained release than LUVfuso VAN, LUVcat VAN, and free VAN. The formulations were stable over 180 days at 4°C, except for LUV VAN, which was stable up to 120 days. The MIC values for liposomal formulations and free VAN ranged from 0.78 to 1.56 µg/ml against both tested strains, with no difference in the inhibition of biofilm formation as compared to free VAN. However, when treating mature biofilm, encapsulated LUVfuso VAN increased the antimicrobial efficacy as compared to the other liposomal formulations and to free VAN, demonstrating a better ability to penetrate the biofilm. Conclusion: Vancomycin encapsulated in fusogenic liposomes demonstrated enhanced antimicrobial activity against mature S. aureus biofilms.

Liposomes as a Nanoplatform to Improve the Delivery of Antibiotics into Staphylococcus aureus Biofilms

“…To evaluate the influence of the charge, stearylamine (SA) was selected as a hydrophobic surface modifier to achieve positively charged liposomes, while DPPG and DMPG were included in the lipid composition to obtain negatively charged liposomes. All antibiotics were also incorporated in liposomes with fusogenic properties, since it has been described that this lipid composition increased their capacity to penetrate biofilm structure and fuse with the outer membrane of bacteria, due to the fluidity of the phospholipid bilayer [ 10 , 12 , 62 ]. In addition, the use of these types of lipids, such as DOPE in combination with CHEMS, promotes the destabilization of the liposome lipid bilayer and stimulates the release of incorporated antibiotics at a lower pH [ 63 ].…”

“…Bacterial biofilms are composed of bacteria aggregates, involved in an extracellular matrix, containing proteins, polysaccharides and DNA [ 9 ]. This structure provides an excellent mechanism of defense, against immune response and blocks the antibiotic penetration, leading to extended hospitalization periods and high social costs [ 8 , 10 , 11 , 12 ].…”

“…Three antibiotics were chosen for an initial screening, regarding susceptibility tests and incorporation in liposomes. The selected antibiotics were the fluoroquinolone, levofloxacin (LEV), usually recommended for the treatment of S. aureus bone and joint infections [ 24 ], the glycopeptide vancomycin (VCM), the gold standard antibiotic in clinical practice against S. aureus infections [ 12 , 25 ], and the rifamycin, rifabutin (RFB), a broad-spectrum antibiotic covering S. aureus strains [ 26 ]. To achieve our goal, the design and characterization of liposomes with different lipid compositions for each antibiotic were accomplished and the susceptibility of a S. aureus methicillin-susceptible strain (MSSA), both in planktonic and biofilm forms, was assessed.…”

Hybrid Pectin-Liposome Formulation against Multi-Resistant Bacterial Strains

“…In the in vitro release test, ofloxacin-loaded liposomes released around 90% after 10 h of experiment [9]. In another report, specialized (fusiogenic and cationic) liposomes composed of phosphatidylcholine/cholesterol/α-tocopherol released around 70% vancomycin after 10 h [31]. In addition, the acidic liposomes containing PCT in their inner aqueous phase (PCT@LIP/NOR) have driven a different release kinetic profile (first order) of NOR in comparison to LIP/NOR and PCT-LIP/NOR (Korsmeyer-Peppas), corroborating its more complex supramolecular structure.…”

“…These vesicles are composed of phospholipids that can be internalized by bacterial membranes [30], favoring the delivery of antimicrobial agents in situ. However, the huge increase of multi-resistant strains have encouraged the development of modified liposomes in order to increase the bactericidal effect of antimicrobial drugs [5], so that fusogenic and cationic liposomes containing vancomycin have been used against nosocomial and community-acquired infections [31].…”