Green-synthesized gold nanoparticles: as emerging tools to combat antimicrobial resistance and therapeutic applications in poultry.

Antimicrobial resistance (AMR) nowadays has become a serious concern for poultry industry due to rapidly growing microbes. The frequent and overuse of antimicrobial drugs in the past few decades has raised serious queries in terms of AMR. To overcome AMR, various natural products, including probiotics, phytochemicals, and nanoparticles, have emerged as promising therapeutic alternatives. Among all, green-synthesized nanoparticles are increasingly being adopted to restore gut health and disease resilience. Green synthesis of gold nanoparticles (AuNPs) is a revolutionary technique in veterinary medicine. Their synthesis involves natural biomolecules, microorganisms, and plant extracts, rather than traditional chemicals. They can improve the therapeutic potential by causing damage to lethal pathogens of poultry, including bacteria, viruses, and protozoans. These nanoparticles rupture the bacterial cell wall and cell membrane, causing inhibition of biofilm formation, producing reactive oxygen species (ROS), causing oxidative stress. They also cause hindrance to the electron transport chain (ETC) and ultimately lead to leakage of cytoplasmic contents. They can also be used as additives along with antibiotics to demonstrate synergistic effects, providing a broad attacking strategy. However, AuNPs have several limitations, including resistance against pathogenic microbes, but the main focus of the study is to develop multifunctional NPs that have multiple functions in a single structure, like integrating antimicrobials, gene therapy, imaging, target drug delivery, real-time monitoring of infection, gene suppression resistance, diagnostic, and theranostics agents. This review discusses the green synthesis of AuNPs, their antimicrobial potential, applications, and how they combat disease-causing AMR pathogens, as well as their limitations and future perspectives, along with their physicochemical characteristics.