Synthesis, Characterization, and Antibacterial Activity of Manganese Doped, Zinc Oxide Nanoparticles against Multidrug-Resistant Acinetobacter baumannii

Background: The rapid emergence of multidrug resistant (MDR) Acinetobacter baumannii has become a critical global healthcare challenge, necessitating the development of alternative antimicrobial strategies. Metal oxide nanoparticles have attracted considerable attention because of their broad-spectrum antibacterial activity. Manganese (Mn)-doped zinc oxide (ZnO) nanoparticles exhibit enhanced physicochemical properties that may improve antimicrobial performance. This study aimed to synthesize and characterize Mn doped ZnO nanoparticles and evaluate their antibacterial activity against a clinical MDR A. baumannii isolate. Methods: Mn-doped ZnO nanoparticles were synthesized using a co-precipitation method and characterized by UV Visible Spectroscopy, X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), and Atomic Absorption spectroscopy (AAS) to determine their optical, structural, morphological, and elemental properties. Antibacterial activity was assessed against a clinical MDR A. baumannii isolate using the broth microdilution assay at nanoparticle concentrations of 10, 20, and 30 μg/mL. Results: Characterization analyses confirmed the successful synthesis of crystalline Mn-doped ZnO nanoparticles with a hexagonal wurtzite structure and an average crystallite size of approximately 28 nm. The nanoparticles exhibited concentration-dependent antibacterial activity, producing growth inhibition of 45.6%, 62.7%, and 91.7% at concentrations of 10, 20 and 30 μg/mL respectively. The highest concentration resulted in near-complete suppression of bacterial growth, demonstrating the strong antibacterial efficacy of Mn-doped ZnO nanoparticles against MDR A. baumannii. Conclusions: Mn-doped ZnO nanoparticles demonstrated potent in vitro antibacterial activity against multidrug-resistant A. baumannii, highlighting their potential as a promising nanomaterial for combating antibiotic-resistant bacterial infections. These findings provide a foundation for further investigations into their antibacterial mechanisms, biocompatibility, and in vivo therapeutic applications.