Antibacterial activity of silver and zinc nanoparticles against Vibrio cholerae and enterotoxic Escherichia coli

Abstract

Vibrio cholerae and enterotoxic Escherichia coli (ETEC) remain two dominant bacterial causes of severe secretory diarrhea and still a significant cause of death, especially in developing countries. In order to investigate new effective and inexpensive therapeutic approaches, we analyzed nanoparticles synthesized by a green approach using corresponding salt (silver or zinc nitrate) with aqueous extract of Caltropis procera fruit or leaves. We characterized the quantity and quality of nanoparticles by UV–visible wavelength scans and nanoparticle tracking analysis. Nanoparticles could be synthesized in reproducible yields of approximately 108 particles/ml with mode particles sizes of approx. 90–100 nm. Antibacterial activity against two pathogens was assessed by minimal inhibitory concentration assays and survival curves. Both pathogens exhibited similar resistance profiles with minimal inhibitory concentrations ranging between 5 × 105 and 107 particles/ml. Interestingly, zinc nanoparticles showed a slightly higher efficacy, but sublethal concentrations caused adverse effects and resulted in increased biofilm formation of V. cholerae. Using the expression levels of the outer membrane porin OmpT as an indicator for cAMP levels, our results suggest that zinc nanoparticles inhibit adenylyl cyclase activity. This consequently deceases the levels of this second messenger, which is a known inhibitor of biofilm formation. Finally, we demonstrated that a single oral administration of silver nanoparticles to infant mice colonized with V. cholerae or ETEC significantly reduces the colonization rates of the pathogens by 75- or 100-fold, respectively.

The antimicrobial activity of nanoparticles: present situation and prospects for the future

“…144 However, studies have shown that NPs can act on the ion channels in bacterial biofilms, thereby regulating the metabolic activity of bacteria. Salem et al 145 showed that the amounts of Ag NPs and ZnO NPs necessary for growth inhibition (minimal inhibitory concentration assay) and for inhibition of metabolic activity (INT assay) were nearly equal. The result suggested that the dominant antimicrobial targets of the NPs are the metabolic pathways of bacteria.…”

Antibacterial Activity of Biogenic Platinum Nanoparticles: An In vitro Study

“…In recent past nanoparticles have shown promising results to inhibit microorganisms and drug resistant microorganisms. Several studies conducted around the glove are reporting the antimicrobial properties of various nanoparticles such as silver, gold and zinc against a broad range of nanoparticles (Salem et al, 2015;Zhang et al, 2015;Thomas et al, 2014). However the activity of the particles can variety based on the method they are prepared and because of particle size.…”

Antibacterial Activity of Biosynthesized Silver Nanoparticles From Viola Serpens Against Multi Drug Resistant Strains of Staphylococcus Aureus and Pseudomonas Aeruginosa

“…[13] An earlier study exhibited that plant mediated synthesized Silver nanoparticles can inhibit the biofilm formation and reduce the threat of drug resistance. [14] The present study revealed that high antibacterial potential of silver nanoparticles was found against tested strains of P. aeruginosa even at very low concentration of AgNPs (in μg/ml) in comparison to plant extracts and reference drug used. Our findings also correlate with the study previously reported by researchers which evaluated the antibacterial effect of Silver nanoparticles against multi-drug resistant strains of P. aeruginosa.…”