Phytoextracts-Synthesized Silver Nanoparticles Inhibit Bacterial Fish Pathogen Aeromonas hydrophila

Abstract

Fish disease is a major stumbling block towards sustainable growth of the fisheries sector. Aeromonas hydrophila, which is a major infectious aquatic pathogen is reportedly the causative agent of ulcers, fin-rot, tail-rot, hemorrhagic septicemia in fish, and has reportedly developed resistance against many of the available antibiotics. In this context, the inhibitory function of silver nanoparticles (AgNPs) against A. hydrophila was studied to evaluate its possible application in aquaculture as alternative to antibiotics. AgNPs were synthesized using the leaf extracts of subtropical plants Mangifera indica (Mango), Eucalyptus terticornis (Eucalyptus), Carica papaya (Papaya) and Musa paradisiaca (Banana). The absorbance maxima, size range and shape of the AgNPs as characterized by the UV-Vis spectroscopy, high resolution transmission electron microscopy (HR-TEM), and energy dispersive X-ray spectroscopy (EDX) were, Mangifera-442, 50-65 nm, ovular; Eucalyptus-465, 60-150 nm, oval; Carica-442, 25-40 nm, round, irregular; and Musa-454, 10-50 nm, round, irregular, respectively. Well-diffusion of these AgNPs for their antimicrobial characteristics exhibited that, the papaya leaf extract synthesized AgNPs had maximum antimicrobial activity at 153.6 μg/ml concentrations, and that from the eucalyptus leaves was least effective. As observed, the potency of the nanoparticles enhanced with the decrease in particle size, from 60-150 nm in eucalyptus to 25-40 nm in papaya. Due to its purely natural sourcing, phytosynthesized AgNPs can be applied as alternative to antibiotics and other biocides as a cost-effective and eco-friendly therapeutic agent against A. hydrophila stimulated diseases in aquatic animals.

Keywords: Aeromonas hydrophila; Anti-microbial activity; Phytosynthesis; Silver nanoparticle.

Fig. 1

Photograph showing a 1 mM silver nitrate, AgNPs synthesized from b Eucalyptus, c mango, d papaya, e banana leaf extracts

Fig. 2

UV–Vis spectrum of the AgNPs during synthesis using a Eucalyptus, b mango, c papaya and d banana leaf extracts

Fig. 3

a Size, b histogram of the size distribution, c HEED and d EDX of the AgNPs synthesized from Eucalyptus leaf extract

Fig. 4

a Size, b histogram of the size distribution, c HEED and d EDX of the AgNPs synthesized from mango leaf extract

Fig. 5

a Size, b histogram of the size distribution, c HEED and d EDX of the AgNPs synthesized from papaya leaf extract

Fig. 6

a Size, b histogram of the size distribution, c HEED and d EDX of the AgNPs synthesized from banana leaf extract

Fig. 7

Antibacterial activity of the AgNPs synthesized using a Eucalyptus, b mango, c papaya and d banana leaf extracts, against Aeromonas hydrophila. Wells ii, iii, iv and v were loaded with 153.6, 76.8, 30.7 and 15.3 μg/ml AgNPs, while well i (control) in each case was loaded with the respective pure leaf extract alone