Biosynthesis of silver nanoparticles and study of their activities against drug-resistant pathogenic organisms.

Objective To determine biosynthesis of silver nanoparticles (AgNPs) by different bacteria and Aspergillus species and to study the effect of these prepared AgNPs alone and in combination with selected antimicrobial agents against resistant bacteria and Candida. Methods AgNPs were synthesized using different bacterial isolates (Bacillus cereus, Escherichia coli, Enterococcus faecalis, Pseudomonas aeruginosa, and Aspergillus niger). AgNPs were characterized by ultraviolet/visible spectrophotometer, transmission electron microscopy, scanning electron microscope, and energy-dispersive radiograph spectroscopy analysis. Antimicrobial activity of biosynthesized AgNPs was assessed alone and in combination with antimicrobial agents against resistant bacteria and Candida. Cytotoxicity assay of biosynthesized AgNPs was also assessed. Results The AgNPs thus obtained were confirmed through observed color change, and their evaluation using ultraviolet/ visible showed the highest optical density at 410–430 nm wavelength. Transmission electron microscopy and scanning electron microscope showed that the small particle size ranged and strong signal was detected by the energydispersive radiograph spectroscopy analysis. Antimicrobial efficacy was increased in combination with biosynthesized AgNPs (P<0.001). There was low cytotoxic activity of B. cereus AgNPs on Medical Research Council cell strain 5 (MRC-5) cells. Conclusion B. cereus-biosynthesized AgNPs have the best antimicrobial effect against resistant bacteria and Candida, in addition to their low cytotoxicity effect on normal cells. [ABSTRACT FROM AUTHOR]