Antibacterial effect of biogenic silver nanoparticles on resistant bacteria

DORADO RITA DANIELA; PÉCORA LUCIANA A; HOLLMANN AXEL; RODRIGUEZ MÓNICA; CECILIA RODRÍGUEZ; ROMERO CINTIA; ESPECHE TURBAY M BEATRIZ

Congreso; Congreso SAIB 2023; 2023

Sociedad Argentina de Investigaciones en Bioquimica y Biologia Molecular

Antimicrobial resistance is currently a topic of global concern, which demands attention at different levels, and one of them is the need for novel antimicrobials effective against multidrug resistant (MDR) strains. Silver nanoparticles (AgNPs) enhances the antimicrobial activity of silver ions and, due to their versatile antimicrobial mechanism, makes them strong candidates for evading resistance mechanisms developed by microorganisms. Our aim was to develop AgNPs through an eco-friendly process and evaluate their antimicrobial activity against MDR strains. AgNPs were synthesized from an extracellular extract of Bacillus sp (AgNP@bc) and were characterized by UV-Vis and vibrational spectroscopy (FTIR), surface and transmission electron microscopy (SEM and TEM, respectively), particle size (DLS) and zeta potential (pZ). The antimicrobial effect was evaluated by agar diffusion and minimum inhibitory concentration, in Gram positive and Gram negative control strains, as well as in MDR strains isolated from clinical settings. The effect of AgNP@bc on the cell envelope (pZ of microorganisms) was determined, and the possible mechanisms of action on the cytoplasmic membrane (non-polar fluorescent probe 1-N-phenylnaphthylamine; NPN), and the ability to produce species reactive oxygen (ROS, nitrotetrazoyl blue reduction technique, NBT).The results demonstrated that through biogenic synthesis, AgNPs with spherical morphology, with a negative surface charge, were formed by the action of exopolysaccharides present in the extracellular extract. The AgNP@bc exhibited antimicrobial activity against Gram positive and -negative strains whose mechanism of action was strain dependen, in Gram negative strains disrupting the cytoplasmic membrane while in Gram positive strains the effect was associated with the production of ROS. The AgNP@bc were active on Gram-negative clinical strain sensitive to colistin, suggesting a similar possible mechanism. These results demonstrate that AgNP@bc are promising candidates for new antimicrobial therapies against MDR strains. Future studies are needed to evaluate their clinical application.