Green Synthesis of Silver Nanoparticles Using Terminalia arjuna Extract and their Antibacterial Activity Against ESBL-producing Escherichia coli

Background: The emergence of resistance among Escherichia coli bacteria, particularly those expressing extended-spectrum beta-lactamase enzymes, poses a significant threat to successful antibiotic treatment. Natural plant-based compounds with nanotechnology offer a sustainable method for generating alternative antibacterial agents. Aim: The objective of this study was to generate silver-based nanoparticles using the aqueous extract of Terminalia arjuna and assess their antibacterial efficacy against drug-resistant E. coli. Methods: Bacterial isolates were identified using conventional microbiological methods such as Gram staining, growth characteristics on MacConkey agar, and biochemical testing. Antimicrobial susceptibility was determined using the disc diffusion method in compliance with clinical laboratory guidelines. Resistance genes were detected using a polymerase chain reaction. Silver-based nanoparticles were created using green synthesis by combining an aqueous extract of T. arjuna with silver nitrate solution. Analytical techniques such as ultraviolet-visible spectroscopy, infrared spectroscopy, crystal structure analysis, scanning and transmission electron microscopy, and elemental composition analysis was used for confirmation of nanoparticle. The antibacterial activity was assessed using the agar well diffusion assay. Results: Four of the six bacterial isolates had high resistance to beta-lactam antibiotics and were found to have resistance-related genes. The synthesised nanoparticles were spherical in shape, with an average size of 30 to 35 nanometres and mean zeta potential value of -33.6 mV. Elemental analysis verified the presence of silver as its primary component. The silver-based nanoparticles exhibited potent antibacterial action, with inhibition zones rising proportionately with concentration and reaching up to 18.50±0.50 mm at the highest dose and MIC of 125μg/ml. The silver nanoparticles exhibited moderate cytotoxicity with an IC₅₀ value of 74.236 μg/mL in Vero cell lines. Concentrations below this threshold were found to be biocompatible, indicating potential for safe antibacterial applications. Conclusion: This study demonstrates the successful green synthesis and characterisation of silver nanoparticles using T. arjuna extract. Their proven antibacterial effectiveness against resistant E. coli, along with their biocompatibility, encourages more research into potential therapeutic and pharmacological uses. Major Findings: The green synthesis of silver-based nanoparticles with T. arjuna extract provides an effective friendly alternative for treating multidrug-resistant E. coli, indicating their potential use in future antimicrobial therapeutics.