Synergistic Effect of Biosynthesized Silver Nanoparticles and Natural Phenolic Compounds against Drug-Resistant Fish Pathogens and Their Cytotoxicity: An In Vitro Study

• Main Authors: Ehab Essawy, Mohamed S. Abdelfattah, Mansour El-Matbouli, Mona Saleh
• Format: Article
• Language: English
• Published: MDPI AG 2021-01-01
• Series: Marine Drugs
• Subjects: AgNPs; rutin; heliomycin; synergistic effect; fish pathogens; EPC
• Online Access: https://www.mdpi.com/1660-3397/19/1/22

Fish pathogens causing disease outbreaks represent a major threat to aquaculture industry and food security. The aim of the presented study is to develop safe and effective bioactive agents against two bacterial isolates: <i>Aeromonas hydrophila</i> and <i>Pseudomonas fluorescens</i>. We employed a broth microdilution method to investigate the antibacterial effect of biosynthesized silver nanoparticles (AgNPs); rutin, a natural flavonoid extracted from <i>Ruta graveneoles</i>; and heliomycin, a secondary metabolite produced by marine actinomycetes AB5, as monotherapeutic agents. Moreover, AgNPs in combination with rutin (AgNP + R) and heliomycin (AgNPs + H) were examined for their synergistic effect. The cytotoxic effect of individual bioactive compounds and in combination with AgNPs was investigated on epithelioma papulosum cyprini (EPC) fish cell lines. Individual treatment of AgNPs, rutin, and heliomycin exhibited a dose-dependent antimicrobial activity against <i>A. hydrophila</i> and <i>P. fluorescens</i>. Rutin minimum inhibitory concentration (MIC) showed the lowest cytotoxicity when tested on EPC cell lines, while heliomycin MIC was highly cytotoxic. Combined subtherapeutic doses of AgNPs + R and AgNPs + H displayed additive and synergistic effects against <i>A. hydrophila</i> and <i>P. fluorescens</i>, respectively, with improved results and relative safety profile. The study findings demonstrate that a combination of AgNPs and natural bioactive compounds may represent novel therapeutics fighting fish pathogens potentially affecting the fish farming industry.