Growth Pattern and in vitro Antibacterial Activity of Some Cultivated Herbs against Fish Pathogenic and Food Poisoning Bacteria

Abstract

The global concerns on the deleterious effect of synthetic antimicrobials in the production of food animals call for suitable and sustainable natural alternatives, one of which is the use of herbal products. This study aimed to investigate the growth pattern of some herbs of medicinal values and their antibacterial potentials against some sh pathogenic and food poisoning bacteria, compared with Aquamedics (a synthetic antibiotic) using agar well diffusion assay. The results showed that the number of leaves produced in Euphorbia hirta was more than the leaves produced in E. hererophylla; notwithstanding, E. heterophylla was higher than E. hirta. Ocimum gratissimum showed similar pattern of growth with E heterophylla during the rst 8 weeks while Phyllanthus amarus is characterized with production of higher number leaets at the early growth stages. All the herbal extracts investigated showed presence of avonoids and tannins. The ethanol E. hirta extract (EHE) and Jatropha gossypiifolia extract (JGE) exhibited signicantly higher (P < 0.05) zone of inhibition against Pseudomonas aeruginosa and P. uorescens, compared to other extracts and Aquamedics. The JGE also had higher zone of inhibition against Aeromonas hydrophila (26.67mm), and Streptococcus agalactiae (25.67mm) compared to Aquamedics (22.33mm) and other extracts while EHE, E. heterophylla and Moringa oleifera exhibited similar zones of inhibition, 23.67mm, 23.00mm, 21.67mm, respectively, compared with 22.33mm obtained for Aquamedics against A. hydrophila . The methanol extracts of JGE, EHE and P. amarus extract also exhibited higher zone of inhibition against P aeruginosa, compared to other extracts and the synthetic antibiotic. However, the synthetic antibiotic demonstrated higher zone of inhibition than the aqueous extracts of the herbs, except EHE
which had similar inhibitory activity with Aquamedics against P. uorescens. On the over all, the ethanol extracts seemed to have more potent antibacterial activity than other extracts. The present study has demonstrated the moderately inhibitory activities of the ethanol and methanol extracts of Euphorbia species, gossypiifolia and P. amarus against the food poisoning Pseudomonas species and pathogenic A. hydrophila and S. agalactiae. These extracts are therefore recommended for utilization and further in vivo study as herbal antibacterial agents for sh health management and sh preservation