Silver nanoparticle-induced antimicrobial resistance in Pseudomonas aeruginosa and Salmonella spp. Isolates from an urban lake

Abstract

The antimicrobial properties and widespread incorporation of silver nanoparticles (AgNPs) into consumer products have raised concerns about their potential impact on public health and the environment. This study examined citrate-coated and uncoated AgNPs’ antimicrobial effects on microbial growth and their potential to induce antimicrobial resistance (AMR) in the natural environment. We isolated Pseudomonas aeruginosa and Salmonella spp. from a local lake. We exposed the pathogenic isolates to the AgNPs and examined their impact on antimicrobial susceptibility using the Kirby-Bauer method. Both citrate-coated and uncoated AgNPs caused a significant rapid decline in bacterial population growth. The LOEC of citrate-coated AgNP for the bacterial population was 10-fold lower than that of the uncoated AgNP. The NOECs of citrate-coated and uncoated AgNPs for AMR in Salmonella spp. was <47.8 μg/L and that of P. aeruginosa was 95.5 μg/L. Citrate-coated and uncoated AgNPs induced AMR in Salmonella spp. at 47.8 μg/L and P. aeruginosa at 192.3 μg/L. All AgNP-induced Salmonella spp. isolates were resistant to ampicillin while AgNP-induced P. aeruginosa isolates were resistant to ciprofloxacin and gentamicin. For citrate-coated AgNP antimicrobial susceptibility tests, 13.3 and 17.5% were positive for resistance in P. aeruginosa and Salmonella spp. respectively. Uncoated AgNP antimicrobial susceptibility tests showed 3.3 and 10.8% positive for resistance in P. aeruginosa and Salmonella spp. respectively. The AgNP-induced resistance was concentration-dependent. The findings of this study demonstrate that AgNPs can alter bacterial populations and stimulate AMR in pathogenic bacteria, raising concerns about the potential health risks associated with the contaminants of emerging concern.