Antibacterial Activity of Extracts Derived from Leaves of Ficus elastica Roxb. ex Hornem. (Moraceae) and its Cultivars against Three Aeromonas spp. Strains

Abstract

The present study aimed to evaluate the antimicrobial activity of the ethanolic extracts derived from the leaves of Ficus elastica Roxb. ex Hornem. and its cultivars (Rubra, Robusta, Burgundy, Variegata) against Aeromonas sobria, Aeromonas hydrophila, and Aeromonas salmonicida subsp. salmonicida to evaluate the possible use of this plant in preventing infections caused by this fish pathogen in aquaculture. The leaves of F. elastica and its cultivars, cultivated under glasshouse conditions, were sampled at M.M. Gryshko National Botanic Garden, National Academy of Science of Ukraine. Specifically, the leaves of F. elastica and its cultivars were sampled for our study. Three Aeromonas strains: Aeromonas sobria (K825) and Aeromonas hydrophila (K886), as well as Aeromonas salmonicida subsp. salmonicida (St30), originated from freshwater fish species such as common carp (Cyprinus carpio L.) and rainbow trout (Oncorhynchus mykiss Walbaum), respectively, were isolated in Department of Fish Diseases, National Veterinary Research Institute in Puławy (Poland). Antimicrobial susceptibility of the tested Aeromonas strains was performed by the Kirby-Bauer disc diffusion method according to the recommendations of the Clinical and Laboratory Standards Institute (CLSI, 2014), with some modifications. Our results of the antimicrobial screening revealed, that F. elastica and its cultivars possessed mild antibacterial properties against the A. sobria and A. hydrophila strains. The ethanolic extract derived from leaves of F. elastica ’Variegata‘ exhibited the maximum antimicrobial activity against A. sobria, while the ethanolic extract derived from leaves of F. elastica exhibited the maximum antimicrobial activity against A. hydrophila and Aeromonas salmonicida subsp. salmonicida strains. The results of this study provide baseline information on the potential validity of extracts derived from leaves of F. elastica and its cultivars in the treatment of infections associated with fish pathogen Aeromonas spp..