Effects of bimetallic silver and copper nanoparticles on the proliferation and viability of clinical isolates of Staphylococcus aureus, Klebsiella pneumoniae, and Escherichia coli

Abstract

Bacterial resistance, exacerbated by the indiscriminate use of antibiotics, poses a serious threat to global health. The World Health Organization (WHO) identifies Staphylococcus aureus, Klebsiella pneumoniae, and Escherichia coli as key microorganisms in human infections that exhibit high resistance to conventional treatments. In this context, bimetallic silver-copper nanoparticles (Ag-CuNPs) emerge as a promising alternative with antimicrobial potential; therefore, their antibacterial activity was evaluated against clinical isolates of these three microorganisms. Synthesis and characterization were performed using UV-Vis spectrophotometry and scanning electron microscopy (SEM). Six-hour assays were conducted to evaluate cell proliferation and viability using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) reduction method, followed by 24-hour assays. The Ag-CuNPs significantly inhibited the growth of S. aureus (MIC of approximately 0.8 mg/mL). In contrast, K. pneumoniae and E. coli exhibited hormesis at low concentrations (0.2 and 0.4 mg/mL, respectively), with MICs close to 1 mg/mL. The difference in observed susceptibility may be attributed to the structure of the bacterial cell envelope. The Ag-CuNPs could represent an innovative and low-toxicity therapeutic strategy for combating infections caused by various pathogens, aiming to reduce the antimicrobial resistance crisis.