Abstract
Canadian goldenrod (Solidago canadensis )i s one of the most destructive invasive weeds in South- eastern China. To evaluate its potential application as dietary supplement in red swamp crayfish (Procambarus clarkii), the antibacterial properties of aqueous and ethanol extracts of this plant against three major pathogenic bacteria in crayfish aquaculture were examined. Inhibition zone tests and determination of minimum inhibitory concentration revealed that the extracts had lower antibacterial activity than extracts from two traditional medicinal plants that possess antibacterial properties, garlic (Allium sativum) and cortex phellodendri (Phello- dendron chinense). However, they did exhibit greater antibacterial effects than extracts from another widely used medicinal plant, Sophora flavescens, and an aquatic weed, Alternanthera philoxeroides. Aqueous extracts of Cana- dian goldenrod gave greater inhibition than the ethanol extracts. Crayfish fed a diet with 2% these aqueous extracts exhibited significantly higher enzyme activity of alkaline phosphatase, catalase and phenoloxidase (P<0.05). Based on the results of this study, we conclude that aqueous extracts of Canadian goldenrod are highly promising for the development of new dietary supplement for use in crayfish aquaculture.
Highlights
Bacterial species from numerous Gram-negative genera including Aeromonas and Vibrio can cause asymptomatic bacteremia and bacterial septicemia in freshwater crayfish, with the former condition representing an early phase of the latter
With the growth of intensive crayfish aquaculture, the occurrence of disease outbreaks caused by these bacteria is likely to increase and the consumption of food contaminated with A. hydrophila, A. veronii bv
These results reveal that A. sativum extracts exhibited the strongest antibacterial effects against tested microorganisms followed by P. chinense
Summary
Bacterial species from numerous Gram-negative genera including Aeromonas and Vibrio can cause asymptomatic bacteremia and bacterial septicemia in freshwater crayfish, with the former condition representing an early phase of the latter. Aeromonas is one of the most frequently reported asymptomatic genera that have been isolated from the hemolymph of apparently healthy crayfish[1]. Ingestion of food contaminated with Aeromonas hydrophila and Aeromonas veronii bv. Sobria has been frequently reported to cause gastrointestinal diseases in human[2]. While the abundance of Vibrio species can lead to the development of vibriosis in crayfish, Vibrio parahemolyticus is of great concern for food safety because it is recognized as a human pathogen and is a leading cause of food poisoning especially in Asian countries[3]. With the growth of intensive crayfish aquaculture, the occurrence of disease outbreaks caused by these bacteria is likely to increase and the consumption of food contaminated with A. hydrophila, A. veronii bv. The development of safe therapeutants and the implementation of effective disease control methodologies are urgent requirements for the crayfish culture system and for consumers
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