The range of healing targets for particular Ficus species compiled from local medicines can be competitive with that of broad-spectrum traditional remedies. In the current study, we studied the antimicrobial activity of the ethanolic extracts derived from the leaves of Ficus elastica Roxb. ex Hornem. and its cultivars (F. elastica 'Rubra', 'Robusta', 'Burgundy', 'Variegata') against Aeromonas sobria to evaluate the possible use of this plant in preventing infections caused by this fish pathogen in aquaculture. The current study was conducted as a part of an ongoing project between five universities undertaken in the frame of a cooperation program aimed at the assessment of medicinal properties of tropical and subtropical plants, cultivated in vitro. The leaves of F. elastica and its cultivars, cultivated under glasshouse conditions, were sampled at M. M. Gryshko National Botanic Garden (NBG), National Academy of Science of Ukraine. Specifically, the leaves of F. elastica and its cultivars, i.e. F. elastica 'Rubra', 'Robusta', 'Burgundy', 'Variegata' were sampled for our study. Aeromonas sobria (K825) strain, originated from freshwater fish species such as common carp (Cyprinus carpio L.) and rainbow trout (Oncorhynchus mykiss Walbaum), respectively, was isolated in the Department of Fish Diseases, The National Veterinary Research Institute in Pulawy (Poland). Antimicrobial susceptibility of the tested Aeromonas sobria was performed by the Kirby-Bauer disc diffusion method (1966) according to the recommendations of the Clinical and Laboratory Standards Institute (CLSI) (2014), with our some modifications. Our results of the antimicrobial screening revealed, that F. elastica and its cultivars possessed mild antibacterial properties against the A. sobria strain. The ethanolic extract obtained from leaves of F. elastica 'Variegata' exhibited the maximum antimicrobial activity against A. sobria. Thus, F. elastica and its cultivars (F. elastica 'Rubra', 'Robusta', 'Burgundy', 'Variegata') disclosed mild bioactivity, and this plant can be regarded as a potential source of antibacterial agents. The results of the current study provide a new perspective for the use of various species belonging to the Ficus genus as medicinal plants to improve the antibacterial responses in salmonid aquaculture.
Keywords: Ficus elastica Roxb. ex Hornem., extract, antimicrobial efficacy, Kirby-Bauer disk diffusion technique, fish pathogens, susceptibility, resistance.