Antimicrobial activity of β-lapachone encapsulated into liposomes against meticillin-resistant Staphylococcus aureus and Cryptococcus neoformans clinical strains.

The aim of this study was to determine whether encapsulation of β-lapachone (β-lap) into liposomes interferes with its in vitro antimicrobial activity against meticillin-resistant Staphylococcus aureus (MRSA) and Cryptococcus neoformans clinical strains. Liposomes (β-lap:lipo or β-lap:HPβ-CD-lipo) were prepared using the hydration of thin lipid film method followed by sonication. The in vitro antimicrobial activities of β-lap-loaded liposomes against MRSA and C. neoformans were evaluated using the microdilution method according to the Clinical and Laboratory Standards Institute (CLSI). The liposomes presented a mean particle size ranging from 88.7±1.5nm to 112.4±1.9nm with a polydispersity index ranging from 0.255 to 0.340, zeta potential from -0.26±0.01mV to +0.25±0.05mV and drug encapsulation efficiency from 97.4±0.3% to 98.9±0.4%. β-Lap and β-lap:HPβ-CD had minimum inhibitory concentrations (MICs) ranging from 2mg/L to 4mg/L, whereas the MICs of β-lap-lipo or β-lap:HPβ-CD-lipo ranged from 4mg/L to 16mg/L for the MRSA strains tested. β-Lap and β-lap:HPβ-CD were able to inhibit fungal growth [MIC=2-8mg/L and minimum fungicidal concentration (MFC)=4-8mg/L]. However, β-lap-lipo and β-lap:HPβ-CD-lipo were more efficient, with MICs and MFCs of <4mg/L. These findings suggest that the liposomal formulations tested do not interfere significantly with β-lap antibacterial activity against MRSA and improve its antifungal properties against C. neoformans.