Antibacterial Efficacy of Linezolid Alone and in Combination with Zinc Oxide Nanoparticles against Methicillin-Resistant S. Aureus Clinical Isolates

Abstract

Skin and soft tissue infections caused by methicillin-resistant S. aureus (MRSA) are among the most common bacterial infections. Linezolid is a cortisone drug for the treatment of infections caused by MRSA. However, developing resistance to linezolid creates a hurdle in the treatment of these infections. The present study aimed to determine the activity of linezolid alone and in combination with zinc oxide nanoparticles (ZnO-NPs) for the purpose of reducing resistance and enhancing its efficacy. For this study, MRSA isolates were taken and confirmed by using the antibiotic susceptibility testing method. The minimum inhibitory concentration (MIC) of both antibiotics and nanoparticles against MRSA clinical isolates was done by using the broth microdilution method. A checkerboard assay has used the determination of the combined activity of linezolid and ZnO-NPs. ZnO-NPs displayed a spherical shape with smooth surface morphology and had a mean size of 10 nm to 20 nm, with a zeta potential of 3.57 mV. The activity of ZnO-NPs against MRSA clinical isolates was 200 µg/ml. Almost 81% of isolates were found sensitive to linezolid with MIC lower than 4 µg/ml, and 19% were resistant, having MIC greater than 4 µg/ml. The combination of an antibiotic and nanoparticles reduced the activity of each of them twofold. The current study revealed that both linezolid and ZnO-NPs have antimicrobial activity against MRSA when used alone. The combination of both medications reduces each other's MIC twofold and has an antagonistic impact. Further research is needed to determine the mechanism through which these medications inhibit each other's activity.