Augmented antibacterial activity of cefazolin with silver nanoparticles against Staphylococcus aureus and Escherichia coli

Antibacterial drug resistance is a growing challenge that can be dealt with by introducing novel drugs or improving the efficacy of existing drugs. Combining nanomaterials with existing drugs to enhance drug effectiveness has garnered substantial research attention. Herein, we evaluated the synergistic antibacterial potential of cefazolin and silver nanoparticles (AgNPs) against two resistant strains of bacteria, Escherichia coli (ATCC35218) and Staphylococcus aureus (ATCC6538P). The broth macrodilution method and the Time-Kill assay were used to determine the antibacterial potential of the AgNP-Cefazolin combination. The Propidium Iodide Assay (PIA) and Bicinchoninic acid assay (BCA) were performed to examine the bacterial damage. Both strains showed the same minimum inhibitory concentration (MIC) of 400 μg/ml for cefazolin alone. When combined with AgNPs, both strains observed a significant MIC decrease. AgNPs to cefazolin ratio of 0.063:300 μg/ml exhibited the best antimicrobial activity against Staphylococcus aureus and Escherichia coli. PIA exhibited much fluorescence when cefazolin and AgNPs were used together, indicating significant damage to bacterial cell walls and membranes. Similarly, BCA showed leakage of a considerable amount of bacterial cytoplasmic protein in the media. Our results show that using AgNPs and cefazolin together could be a promising nano-drug against the two tested strains.