In vitro Assessment of Antimicrobial Activity of Zinc Oxide Nanoparticles against Pathogenic Streptococcus parauberis

Abstract

Antibiotic resistance is a global issue that threatens public health. Searching for an eco-friendly antimicrobial agent that shows a positive effect against antibiotic-resistant pathogenic microorganisms is highly recommended. Nano size inorganic compounds have been shown a remarkable antimicrobial activity. The current study aims to assess the in vitro antimicrobial activity of chemically synthesized ZnO nanoparticles (ZnO NPs) against an isolated pathogenic strain of Streptococcus parauberis from an infected fish farm in Ismailia governorate, Egypt. Well diffusion test was performed to provide a qualitative assessment of the antimicrobial activity along with the determination of minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of the tested NPs. Additionally, the effect of NPs on the bacterial cell was investigated via viability test through 2, 3, 5-triphenyl-2H-tetrazolium chloride (TTC) and transmission electron microscopy (TEM) imaging. ZnO NPs showed clear inhibition of the visible bacterial growth at 0.125 mg/ml. and 0.250 mg/ml. as shown by MIC and MBC respectively. The bacterial cell viability was significantly reduced via adherence of the NPs to the cell membranes, and disrupting the membrane integrity along with leakage of the cellular protein that was validated by the protein Bradford assay. Collectively, these findings provide an essential basis for the development of a new strategy that opens a new avenue to curb fish streptococcal infections.