INTERNATIONAL JOURNAL OF BIOMEDICINE http://dx.doi.org/10.21103/Article12(3)_OA20 International Journal of Biomedicine 12(3) (2022) 454-458 ORIGINAL ARTICLE Biotechnology Antibacterial Effcacy of Linezolid Alone and in Combination with Zinc Oxide Nanoparticles against Methicillin-Resistant S. Aureus Clinical Isolates Imran Khan 1 , Sara Ali 2 , Ikram Khan 3 , Salma Mohamed 2 , Sarmir Khan 4 , Feroz Khan 5 , Hassan Higazi 2* 1 Department of Microbiology, Khyber Medical University Peshawar, Pakistan 2 Department of Medical Laboratory Sciences, College of Health Sciences, Gulf Medical University, Ajman, United Arab Emirates 3 School of Life Sciences, Lanzhou University, Gansu province, China 4 National Institute of Genomic and Advanced Biotechnology (NIGAB), National Agricultural Research Centre (NARC), Islamabad, Pakistan 5 Department of Zoology, Pir Mehr Ali Shah Arid Agriculture University, Rawalpindi, Pakistan 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 effcacy. For this study, MRSA isolates were taken and confrmed 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.(International Journal of Biomedicine. 2022;12(3):454-458.). Keywords: nanoparticles • linezolid • zinc oxide • S. aureus • tissue infections For citation: Khan I, Ali S, Khan I, Mohamed S, Khan S, Khan F, Higazi H. Antibacterial Effcacy of Linezolid Alone and in Combination with Zinc Oxide Nanoparticles against Methicillin-Resistant S. Aureus Clinical Isolates. International Journal of Biomedicine. 2022;12(3):454-458. doi:10.21103/Article12(3)_OA20 Abbreviations BMDM, broth microdilution method; CLSL, Clinical Laboratory Standard Institute; FIC, fractional inhibitory concentration; LRSA, linezolid-resistant S. aureus; MIC, minimum inhibitory concentration; MRSA, methicillin-resistant S. aureus; MSSA, methicillin-sensitive S. aureus; SSTIs, skin and soft tissue infections; ZnO-NPs, zinc oxide nanoparticles.