Synergistic antibacterial effect of Persicaria odorata synthesised silver nanoparticles with antibiotics on drug-resistant bacteria

Abstract

For many years, combination therapies with two or more antimicrobial agents have gained interest to address the problem of emerging antibiotic resistance. Several studies have shown that the addition of AgNPs enhances the antimicrobial activity of antibiotics against resistant pathogens. However, the antibacterial activity of phytosynthesised silver nanoparticles (AgNPs) in combination with antibiotics has not been extensively studied. Therefore, this study aimed to investigate the antibacterial activity of the phytosynthesised AgNPs with different antibiotics against two common pathogenic bacteria, namely methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa. A green method was used to produce AgNPs, where Persicaria odorata extract acted as a reducing and stabilising agent in the aqueous synthesis process. The production of AgNPs was verified through various analytical techniques, including ultraviolet–visible spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy, high-resolution transmission electron microscopy and energy-dispersive X-ray. Notably, strong absorption spectrum corresponding to the surface plasmon resonance peaks of AgNPs was found at 436 nm, with particles ranging from 10 to 35 nm. The disc diffusion technique was used to investigate the antibacterial activity of AgNPs, both alone and in combination with antibiotics. Initially, the MRSA and P. aeruginosa showed 100 % resistance to antibiotics, especially ampicillin. However, the disc diffusion result exhibit a significant increase in the inhibition zone when ampicillin-AgNPs, cefoxitin-AgNPs and chloramphenicol-AgNPs were used in combination. In short, the findings of this study showed that AgNPs exhibit a promising synergy when used in combination with antibiotics, opening up possibilities for future combination therapies against antibiotic-resistant pathogens.