Abstract
INTRODUCTION: Silver nanoparticles (AgNPs) are widely utilized for their exceptional antimicrobial properties, but concerns persist regarding their environmental impacts, particularly in soil and water ecosystems. This study compared the effects of chemically and biologically synthesized AgNPs and ionic silver on bacterial communities commonly present in soil and the proliferation of antibiotic resistance in the soil ecosystem. RESULTS AND DISCUSSION: Biologically synthesized AgNPs exhibited the strongest antimicrobial activity, significantly reducing bacterial populations within a day, and demonstrated minimal impacts on the development of antibiotic resistance in long-term. Notably, resistance to ampicillin was lower by 72% in comparison with a control after 90 days in the presence of biologically produced AgNPs, while resistance to tetracycline and kanamycin dropped to nearly negligible levels. In contrast, chemically synthesized AgNPs and ionic silver substantially increased antibiotic resistance in long-term, particularly to ampicillin and chloramphenicol, where resistance levels were 11 to 13 times higher than the controls, respectively. Chemically synthesized AgNPs caused a gradual rise in resistance, while ionic silver induced consistently elevated resistance throughout the study. CONCLUSIONS: These differences highlight the complex interplay between nanoparticle composition and bacterial adaptation. The findings suggest that biologically synthesized AgNPs are a promising environmentally friendly alternative, reducing bacterial resistance and mitigating the risks associated with silver-induced antibiotic resistance in soil ecosystems. They have greater potential for sustainable applications while addressing critical concerns about antimicrobial resistance and environmental safety.