A Novel Ag/AgCl/Ag3PO4 Nanocomposite Demonstrates Potent Antibacterial Activity Against Multidrug-Resistant and Pan-Resistant Pathogenic Isolates of Acinetobacter baumannii

Acinetobacter baumannii is a microorganism of major global clinical importance, whose carbapenem-resistant phenotype is considered a priority target for the development of new antimicrobial agents. Carbapenem-resistant A. baumannii is associated with healthcare-associated infections and exhibits high mortality rates, prolonged hospital stays, and extensive use of intensive care units. As a control strategy, green-synthesized silver nanoparticles have gained increasing attention. Based on this, the aim of this study was to synthesize a novel triphasic silver nanocomposite, characterize it, and evaluate its antibacterial activity against extensively drug-resistant and pan-drug-resistant isolates. The nanocomposite was synthesized using cell-free bacterial supernatant and was physicochemically characterized regarding concentration, size, morphology, and crystallinity. Its antibacterial activity was assessed using broth microdilution and time–kill assays, followed by toxicity assays using human erythrocytes. A nanoscale and stable nanocomposite was obtained and was composed of metallic silver, silver chloride, and silver phosphate, which exhibited antibacterial activity against all tested isolates. In the toxicity assay, the nanocomposite demonstrated low toxicity and a high selectivity index. These findings demonstrate that Ag/AgCl/Ag3PO4 nanocomposite exhibits strong activity against resistant phenotypes for which therapeutic options are limited, highlighting its potential as a control strategy against this pathogen.