Antibacterial Activity of Cow’s Milk Silver Nanoparticles Synthesized across Various pH against Clinically Isolated MDR Staphylococcus aureus

Authors: Akshata G Athreya , Ismail Shareef M and S M Gopinath

DOI: 10.23880/nnoa-16000214

Volume 6, Issue 3

Abstract

The study aims to evaluate the antibacterial activity of silver nanoparticles (AgNPs) from pasteurized cow’s milk synthesized across various pH (3, 5, 7, 9 and 11) along with study of synergy with the selected antibiotics against the clinically isolated MDR Staphylococcus aureus (S. aureus). The results indicated successful synthesis of AgNPs across pH which were characterized using: a) UV–visible spectroscopy which displayed shifts in absorption peaks from 380 to 460 nm and b) Transmission Electron Microscopy (TEM): It confirmed the range of particles sizes between 10 to 100 nm. Antibiotic sensitivity test confirmed S. aureus as a potential MDR as it was resistant to over 80% of the antibiotics. Antibacterial studies of AgNPs (50 and 75 µl) across pH were performed using disc diffusion method vis-à-vis positive control (Antibiotics- Erythromycin, Ampicillin, Nalidixic acid, Cefazolin and Tetracycline) and negative control (cow’s milk+D.H2O). Results revealed AgNPs synthesized at pH 3, 7 and 9 exhibited 10-13 mm inhibition zones whereas AgNPs at pH 5 and 11 failed to exhibit any activity. The synergistic effect (antibiotics+AgNPs) exhibited greater sensitivity than its individual effects of either AgNPs or antibiotic in cases of 3,7 and 9 pH synthesized AgNPs. Synergistic effect of AgNPs was well observed with Erythromycin and Nalidixic acid followed by other antibiotics. Thus the results obtained indicated the possibility of cow’s milk synthesized AgNPs as an alternate to the current antibiotics to treat MDR bacteria. 

Keywords: AgNPs; Antibacterial; Antibiotics; Cow’s Milk; MRSA; pH

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