Faculty of Medical Sciences, University of Sri Jayewardenepura.
Abstract
Objectives: Biosynthesis and characterization of silver nanoparticles (AgNPs) from Escherichia coli,Acinetobacter baumannii and Staphylococcus aureus and determination of antimicrobial activityagainst selected pathogens.Methods: E. coli (ATCC 25922), A. baumannii (clinical strain), S. aureus (ATCC 25923) were culturedin nutrient broth medium and used for biosynthesis of AgNPs. AgNO3 concentration, pH, incubationtime and temperature were optimized for AgNP biosynthesis. Antimicrobial activity of the synthesizedAgNPs was studied using the well diffusion assay.Results: All the selected bacteria produced silver nanoparticles at alkaline pH when the concentrationof AgNO3 was greater than 0.3 g/L. The optimum reaction temperature was 60oC. UV-Visiblespectroscopy with a maximum absorbance of approximately 420 - 430 nm confirmed the presence ofAgNPs. AgNPs produced by S. aureus resulted in larger zone of inhibition (ZOI) against the selectedpathogens where AgNPs produced by E. coli showed comparatively smaller ZOI. Gram negativebacteria (E.coli, P. aeruginosa) were more sensitive to AgNPs compared to gram positive bacteria(Methicillin Resistant S. aureus, S. aureus) and fungal species (Candida albicans).Conclusion: AgNPs produced by S. aureus are the most effective among the tested AgNPs while E.coli produced the least effective AgNPs
