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Microbiological evaluation of azithromycin-loaded elastic liposomes for the topical therapy of skin infections

Background: The effectiveness of topically applied antibiotics is often reduced because of the insufficient local drug concentration achieved, increase in antibiotic-resistant strains, biofilm formation or inability of drug to reach the site of action. The use of liposomes represents a promising approach for the effective topical delivery of antibiotics and overcoming drug-resistant strains in the skin.1 Objective: The purpose of this study was to evaluate in vitro efficacy of the two types of azithromycin-loaded elastic liposomes against Staphylococcus aureus and methicillin-resistant S. aureus (MRSA) strains. Methods: Deformable liposomes (DLs) and propylene glycol-containing liposomes (PGLs) encapsulating azithromycin were prepared by film-hydration method followed by extrusion through 400 and 200 nm pore sized membranes. The non-encapsulated drug was separated by ultracentrifugation method and the liposomes were tested in vitro against S. aureus and 5 different MRSA strains, both planktonic and biofilm forming bacteria.2 For comparison, conventional liposomes with azithromycin (CLs) were prepared and evaluated under the same conditions. Results: All the liposomes were negatively surface charged with average diameters 132-165 nm. DLs enabled increased encapsulation of azithromycin (64%) in comparison to PGLs (56%) and CLs (52%), and were characterized with more elastic bilayers than PGLs. DLs and PGLs exhibited equal antibacterial activities against S. aureus and MRSA strains with minimal inhibitory concentrations ranging between 0.5-1 µg/ml, compared with 1-4 µg/ml for CLs and 2-8 µg/ml for free azithromycin. Both types of elastic liposomes were also more effective at preventing biofilm formation than the CLs and particularly the free azithromycin. Conclusion: Comparison of the two types of elastic liposomes demonstrated better in vitro anti-biofilm activity of DLs, thus proving its potential for the topical treatment of MRSA-caused infections.

Elastic liposomes ; Azithromycin ; Skin

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