Enhanced antimicrobial effects of carvacrol against methicillin-resistant Staphylococcus aureus strains using niosome formulations

Abstract

Methicillin-resistant Staphylococcus aureus (MRSA) causes a wide range of infections and contributes to elevated morbidity, mortality, and healthcare costs. Herbal compounds combined with drug delivery systems could be an effective alternative option for treating resistant bacteria. This study evaluates the antimicrobial prowess of carvacrol-loaded niosomes against MRSA strains. In this study, six carvacrol–niosome formulations with different ratios of Span and Tween were prepared. The physicochemical attributes of the optimized synthesized niosomes were assessed using Fourier-transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) as well as DLS Zetasizer. Encapsulation efficiency (EE) and in vitro drug release were studied. The antibacterial activity of the synthesized carvacrol–niosomes, in concentrations varying between 7.8 and 1000 μg/ml, was evaluated using microdilution broth methods. The optimized niosomes, with a size of 207.3 nm and an impressive EE of 91%, exhibited a spherical structure as confirmed by the electron microscopy analysis. Impressively, these carvacrol–niosomes demonstrated superior antimicrobial effectiveness against S. aureus, reducing MIC levels 4-fold to 62.5 ± 0.0 μg/ml and MBC to 125 ± 0.0 μg/ml, a significant improvement over the 250 ± 0.0 μg/ml MIC and 500 ± 0.0 μg/ml MBC of free carvacrol. Additionally, while empty niosomes showed minimal cytotoxicity with 88.32 ± 1.32% cell viability at 100 μg/ml, free carvacrol led to a marked reduction in viability to 39.46 ± 1.26%. However, niosomes encapsulating carvacrol notably increased cell survival to 59.67 ± 1.62% at this concentration. These findings underscore the enhanced antimicrobial potency of carvacrol when enclosed within niosomes, suggesting its potential as a potent herbal remedy for combating methicillin-resistant S. aureus.