A Comprehensive Review of Nanoparticles in the Fight Against Antimicrobial Resistance.

(1) Background: The escalating crisis of multidrug-resistant (MDR) bacteria presents a formidable threat to global public health, necessitating the urgent development of alternative antimicrobial strategies. Nanoparticles (NPs) have emerged as a promising frontier in this effort, leveraging their unique physicochemical properties and multi-modal mechanisms of action to combat bacterial infections. This systematic review aims to comprehensively evaluate the current body of evidence on the dynamic interplay between nanoparticles and bacterial resistance. (2) Methods: A comprehensive search of electronic databases, including PubMed, Scopus, and Web of Science, was performed using a combination of keywords and Medical Subject Headings (MeSH) terms to identify relevant primary research articles. Eligibility criteria focused on studies evaluating the antimicrobial effects of nanoparticles on MDR bacterial strains, reporting on mechanisms of action, efficacy, or resistance development. (3) Results: The synthesis of findings revealed that nanoparticles exert their antimicrobial effects through multiple pathways, including the generation of reactive oxygen species (ROS), direct disruption of bacterial membranes, and the release of toxic ions. However, the analysis also confirmed that bacteria have evolved sophisticated defense mechanisms against nanoparticles, including surface modifications that prevent adhesion, upregulation of efflux pumps, and chemical neutralization of toxic ions. (4) Conclusions: Nanoparticles represent a potent and versatile tool in the global effort to combat antimicrobial resistance. Their long-term efficacy is not guaranteed, as bacteria have shown a remarkable capacity for adaptation. The future of this field lies in the development of rationally designed nanoparticle systems that not only possess intrinsic antimicrobial activity but also actively disarm bacterial resistance mechanisms. This includes the strategic use of synergistic combinations with conventional antibiotics and the exploration of resistance-agnostic approaches like nanotoxoid vaccines.