Biosynthesized gold nanoparticles from Proteus mirabilis: A synergistic strategy against multidrug-resistant Gram-negative bacteria.

Gold nanoparticles (AuNPs) are increasingly explored as antimicrobial agents for the detection and treatment of multidrug-resistant (MDR) bacterial infections. This research tries to establish an eco-friendly, biological process for synthesizing AuNPs using Proteus mirabilis and studies their antibacterial efficacy against MDR Gram-negative pathogens and their potential to enhance standard antibiotic efficacy. Using the Vitek-2 system, 51 P.mirabilis isolates were analyzed, of which 74.5 % were MDR. Netilmicin was effective against 75 % of these isolates. P.mirabilis extracellularly biosynthesized AuNPs, which were then characterized by XRD, FTIR, TEM, and FE-SEM. Characterization showed AuNPs measuring ∼6-12 nm in size; the presence of amino and amide groups from FTIR spectra; and predominantly spherical or ellipsoidal morphology. Antibacterial activity, through broth microdilution, revealed that biosynthesized AuNPs inhibited Gram-negative bacilli at MICs of 156-1250 μg/mL. Moreover, biosynthesized AuNPs enhanced the effectiveness of antibiotics at low concentrations. Notably, when biosynthesized AuNPs were combined with ceftriaxone (commercial antibiotic), a marked synergistic effect was observed (P < 0.0001), with significantly enhanced prevention of pathogens compared to ceftriaxone used alone. These findings marched the function of biosynthesized AuNPs as adjuvants in drug development against MDR infections.