Antibacterial Activity of Extracts Derived from Leaves of Ficus lyrata Warb. and its Cultivar Bambino against Some Fish Bacterial Strains

Abstract

The bioactive compounds present in various plant extracts offer a sustainable and environmentally friendly approach to the control of bacterial infections in farmed fish, thus contributing to the promotion of animal health, food safety and environmental sustainability in aquaculture. In the present study, we evaluated the antimicrobial activity of the ethanolic extracts of the leaves of Ficus lyrata Warb. and its F. lyrata cv. Bambino against Aeromonas sobria, Aeromonas hydrophila and Aeromonas salmonicida subsp. salmonicida, Serratia liquefaciens, Yersinia ruckeri, Pseudomonas fluorescens, Shewanella putrefaciens, to evaluate their possible use of these plants in the prevention of infections caused by these fish pathogens in aquaculture. The isolates used in our studies were Aeromonas sobria (K825), Aeromonas hydrophila (K886) and Aeromonas salmonicida subsp. salmonicida (St30), Serratia liquefaciens (Pt521), Yersinia ruckeri (UP 2), Pseudomonas fluorescens (Pt 433), Shewanella putrefaciens (St15). These strains, derived from freshwater fish species such as common carp (Cyprinus carpio L.) and rainbow trout (Oncorhynchus mykiss Walbaum), were isolated at the Department of Fish Diseases, National Veterinary Research Institute in Puławy (Poland). The antimicrobial susceptibility of the tested strains was determined by the Kirby-Bauer disc diffusion method (1966), according to the recommendations of the Clinical and Laboratory Standards Institute (2006, 2014), with our slight modifications. The results of our study showed that a group of Aeromonas strains showed resistance to F. lyrata and F. lyrata cv. Bambino extracts compared to oxytetracycline and enrofloxacin activity. Serratia liquefaciens, Yersinia ruckeri and Pseudomonas fluorescens strains were also resistant to the ethanolic extracts from the leaves of F. lyrata and its cv. Bambino. On the other hand, the Shewanella putrefaciens strain was sensitive to the ethanolic extracts of the leaves of F. lyrata and its cv. Bambino. The percentage increase in zone inhibition diameter for the F. lyrata cv. Bambino leaf extract was 43.3% (p <0.05) compared to oxytetracycline activity. This finding suggests the presence of bioactive compounds in F. lyrata leaves with antimicrobial properties against selected bacterial strains. It highlights the potential of this botanical resource to combat bacterial infections in aquaculture. In conclusion, the antibacterial activity demonstrated by F. lyrata and F. lyrata cv. Bambino leaf extracts against fish bacterial strains highlights their potential as valuable resources for disease prevention and treatment in aquaculture. Continued research efforts to elucidate their mechanisms of action, optimise their formulation, and validate their efficacy in vivo will further enhance their utility and facilitate their integration into sustainable aquaculture production systems.