Ocimum sanctum mediated silver nano particles showed better antimicrobial activities compared to citrate stabilized silver nano particles against multidrug resistant bacteria

Abstract

AimThough there are many chemical and physical techniques available for the synthesis of antimicrobial silver nanoparticle (AgNPs), but the green synthesis is the most emerging method of synthesis. However no comparative study was found evaluating the antimicrobial activities of chemically synthesized AgNPs with those synthesized by green methods. This article outlines the synthesis of AgNPs chemically by sodium citrate and also by a green method using aqueous extract of Ocimum sanctum to compare the effect of the AgNPs synthesized by both the methods against multidrug resistant (MDR) bacterial isolates from hospital wastes. MethodsMDR bacterial strains were isolated from hospital wastes and were identified as Staphylococcus aureus and Bacillus megaterium. Citrate stabilized AgNPs were synthesized by dissolving silver nitrate in water. The green synthesis of AgNPs was carried out by reducing silver nitrate by aqueous extract of O. sanctum. The formation of AgNPs were characterized by UV-VIS spectrophotometer and the size was confirmed by nano particle size analyser. The antimicrobial studies were initially carried out by KirbyeBauer’s disc plate method followed by the determination of minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) against the MDR bacterial isolates. ResultsThe size of the citrate stabilized AgNPs were found to be 120 nm and 157.2 nm for the AgNPs synthesized by the aqueous extract of O. sanctum. The MIC and MBC values of citrate stabilized AgNPs were found to be 60, 160 mg/mL and 80, 160 mg/mL respectively against S. aureus and B. megaterium. The MIC and MBC values of AgNPs synthesized by the aqueous extract of O. sanctum were found to be 40, 120 mg/mL and 80, 140 mg/mL respectively against S. aureus and B. megaterium. ConclusionThe results obtained by the green method were found to be more encouraging which encourage more research on green synthesis of antimicrobial AgNPs.