Preliminary in vitro screening of the antibacterial activity of leaf extracts from various Ficus species (Moraceae) against Yersinia ruckeri

Abstract

Remarkable progress in the field of antibacterial herbal therapy has been made in recent decades in response to the development of drug-resistant pathogens in aquaculture. Studies have focused on the in vitro antimicrobial activity screening of ethanolic extracts of various plants belonging to the genus Ficus. The aim of the present study was to evaluate the antibacterial efficacy of ethanolic extracts of various Ficus species against Yersinia ruckeri. In vitro tests for antibacterial activity revealed that ethanolic leaf extracts of various Ficus species and their cultivars offer a promising alternative to antibiotics and chemotherapeutics for controlling the growth of Y. ruckeri. In our study, ethanolic extracts obtained from leaves of F. natalensis subsp. leprieurii and F. macrophylla proved effective against a bacterial strain at a dose of 400 μl standardized inoculum (10⁸ CFU ml^-1). It should be noted that Y. ruckeri demonstrated an intermediate susceptibility to more extracts derived from the leaves of Ficus species. Our investigation showed that among the various Ficus species, ethanolic leaf extracts of ten Ficus species against Y. ruckeri were the most effective. The effect of the leaf extracts that expressed the highest antimicrobial activity (F. macrophylla, F. natalensis subsp. leprieurii) against Y. ruckeri was comparable to that of gentamicin. Therefore, preliminary screening indicated that the ethanolic leaf extracts of some Ficus species with antibacterial properties can be used in aquaculture as therapeutic and prophylactic agents against fish pathogens, including Y. ruckeri.