LAUSR

Background Nowadays, tuberculosis (TB) is one of the top ten leading causes of mortality worldwide. The emergence of multidrug-resistant (MDR) – and extensively drug-resistant (XDR) – Mycobacterium tuberculosis (M. tuberculosis) is identified as one of the most challenging threats to TB control. Thus, new and safe nano-drugs are urgently required for the elimination of TB. The aim of this study was to investigate the anti-bacterial effects of Ag, ZnO, and Ag-ZnO nanoparticles (NPs) on MDR- and XDR-M. tuberculosis. Materials and methods In this study, Ag, ZnO, and Ag-ZnO NPs were synthesized by the chemical reduction and chemical deposition methods. NPs were characterized using ultraviolet–visible spectroscopy, dynamic light scattering, and transmission electron microscopy. Then, various dilutions of NPs were prepared and their minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) were determined against M. tuberculosis strains using the broth microdilution and agar microdilution methods. Finally, MTT test and cell culture assay were performed. Results The effects of concentrations of 1–128 µg/mL Ag NPs, ZnO NPs, 2Ag: 8ZnO, 8Ag:2ZnO, 3Ag: 7ZnO, 7Ag:3ZnO, and 5Ag:5ZnO on M. tuberculosis strains were investigated. MIC results showed the inhibitory effect of 1 µg/mL of all NPs against XDR-M. tuberculosis. In addition, the concentrations of 4 µg/mL Ag, 8 µg/mL 5Ag:5ZnO, 8 µg/mL 7Ag:3ZnO, 32 µg/mL 3Ag:7ZnO, 16 µg/mL 8Ag:2ZnO, and 64 µg/mL 2Ag:8ZnO inhibited MDR-M. tuberculosis growth. However, MBC results indicated the inability of Ag, ZnO and Ag-ZnO NPs, either in combination or alone, to kill MDR- or XDR-M. tuberculosis. Conclusion To the best of our knowledge, this is the first study to evaluate the effects of Ag and ZnO NPs against MDR and XDR strains of M. tuberculosis. According to the results, Ag and ZnO NPs showed bacteriostatic effects against drug-resistant strains of M. tuberculosis. Therefore, these NPs may be considered as promising anti-mycobacterial nano-drugs. However, further studies are required to affirm the bactericidal effects of these NPs against TB.