Synergistic action of silver nanoparticles synthesized from silver resistant estuarine Pseudomonas aeruginosa strain SN5 with antibiotics against antibiotic resistant bacterial human pathogens

Abstract

This study focuses on the extracellular synthesis of silver nanoparticles (AgNPs), carried out using the culture supernatant of silver resistant Pseudomonas aeruginosa strain SN5 isolated from Mandovi estuarine mangrove water sample. AgNPs were characterized using X-Ray diffraction (XRD) analysis which showed high intensity peaks at 28 degrees and 32.5 degrees, characteristic of silver oxide (Ag2O) and confirmed its crystalline nature by referring Joint Committee on Powder Diffraction Standards (JCPDS), File No. 00-076-1393. Transmission electron microscopy (TEM) analysis revealed the nano sized AgNPS particles in the range of 35 nm - 60 nm. AgNPs showed antibacterial activity against both standard cultures of Gram positive and Gram negative bacterial human pathogens. Moreover, the AgNPs also showed antibacterial activity against ampicillin resistant Staphylococccus aureus strain VN3 and ciprofloxacin resistant Vibrio cholera strain VN1 isolated from Mandovi estuary, Goa India, polluted with human feces, domestic and hotel waste. These AgNPs exhibited better antibacterial activity as compared to AgNPs synthesized from plant extract of Honey suckle mistletoe and star anise. Interestringly, synergistic activity was observed when synthesized AgNPs were used in combination with antibiotics ampicillin and ciprofloxacin against ampicillin resistant Staphylococccus aureus strain VN3 and ciprofloxacin resistant Vibrio cholera strain VN1. Thus these AgNPs can be employed in cosmetics and wound dressings as a nanoweapon to control human bacterial pathogens.