Antimicrobial effects of chitosan silver nano composites (CAgNCs) on fish pathogenic Aliivibrio (Vibrio) salmonicida

Abstract

Chitosan is one of the promising bio-degradable natural products which can be applied in nano forms in disease prevention, and treatment measures in aquaculture. The aim of this study was to develop and investigate the antibacterial function of chitosan-silver nano composites (CAgNCs) against fish pathogenic Aliivibrio salmonicida. Zeta potential and average size of synthesized CAgNCs were +32.1mV and 281nm, respectively. The Ag content of the CAgNCs was 0.643±0.012% (w/w). Antibacterial results revealed that CAgNCs could inhibit the A. salmonicida growth which indicates minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) at 50μg/mL and 100μg/mL, respectively. We confirmed the attachment of AgNPs on the surface of A. salmonicida which indicates the interaction of CAgNCs with the bacterium. Propidium iodide (PI) uptake results suggested that CAgNCs has affected to permeability of cell membrane of A. salmonicida. Also, CAgNCs induced the level of reactive oxygen species (ROS) in concentration and time dependent manner (up to 3h) suggesting that it may generate oxidative stress leading to bacterial cell death. Also, the level of protein was decreased in A. salmonicida cells after CAgNCs (50μg/mL) treatment. DNA fragmentation assay results confirmed that CAgNCs can cause extensive DNA degradation of A. salmonicida which may inhibit the expression and production of bacterial proteins. Toxicity and safety results prove that CAgNCs is not toxic to zebrafish (Danio rerio) at 12.5mg/kg of body weight/day as a feed ingredient and rock bream (Oplegnathus fasciatus) testis cells up to 50μg/μL. Overall results from this study suggest that CAgNCs is potential antibacterial agent to control fish pathogenic bacteria. Statement of relevanceThe fisheries and aquaculture industry can be optimized by using biodegradable nano materials such as chitosan for disease detection, control as well as delivery system of drugs such as hormones, vaccines and nutrients.Aquaculture can be optimized by using biodegradable nano materials such as chitosan for disease detection, control as well as delivery system of drugs such as hormones, vaccines and nutrients.Application of biodegradable nano materials in aquaculture