Antimicrobial and cytotoxic activities of Ag/AgCl nanoparticles biosynthesized by Bacillus cereus against multidrug-resistant Pseudomonas aeruginosa from hospital environments

Hospital surfaces can serve as reservoirs for multidrug resistant (MDR) Pseudomonas aeruginosa․ Continuous and effective surface-directed decontamination strategies are required․ The current study investigates the use of Bacillus cereus-biosynthesized Ag/AgCl nanoparticles as an antimicrobial surface-directed decontamination strategy for drug-resistant Pseudomonas aeruginosa isolated from hospital samples․ An environmental screening of three hospitals found P. aeruginosa in 23 of 224 environmental swabs (10․3%), with sinks being the most contaminated sampling location (39.1% of positive samples)․ Phenotypic profiling revealed a concerning resistance spectrum: 26.1% MDR, 13% XDR, and 4.3% PDR, including a 13.0% incidence of colistin resistance. This is the first time that Ag/AgCl NPs have been biogenic produced from Bacillus cereus biomass‚ incorporating hospital environmental surveillance and the antimicrobial resistance profile with Ag/AgCl NPs biosynthesis and functional characterization toward MDR‚ XDR‚ and PDR local P. aeruginosa isolates‚ as well as the antibacterial and antibiofilm activity assessment of the synthesized Ag/AgCl NPs․ Comprehensive physicochemical characterization (UV-Vis, FTIR, XRD, TEM, FESEM, and zeta potential) confirmed the production of quasi-spherical, face-centered cubic (FCC) Ag/AgCl nanoparticles with a mean crystallite size of 9.58 nm and a zeta potential of − 30.7 mV, indicating moderate to good colloidal stability. The NPs demonstrated robust antibacterial activity, with a MIC of 24 µg/mL against all six tested P. aeruginosa strains, and achieved near-complete biofilm inhibition at concentrations ≥ 24 µg/mL. The Ag/AgCl nanoparticles had cytotoxicity in HaCaT keratinocytes lower than MIC concentration (IC50 = 13.8 µg/mL; SI = 0․575)‚ and the excessive cytotoxicity against normal cells may limit their clinical usage․ Nevertheless‚ additional studies may be required to pursue the use of unmodified Ag/AgCl nanoparticles as antimicrobial agents on vertical and horizontal surfaces in hospitals to eliminate drug-resistant P. aeruginosa from inanimate reservoirs․ Studies to optimize and standardize surface-disinfection methodologies will help determine the practical and safety implications of these systems․ These findings support the potential application of the biosynthesized Ag/AgCl nanoparticles in environmental surface decontamination; however, their effectiveness and safety on hospital surfaces require validation in standardized surface-based and simulated environmental models.