Assessment of some medicinal plant’s potential as anti-infectious agents for red Tilapia fish pathogens

Abstract

Tilapia, a crucial species in global aquaculture, faces significant threats from microbial infections, leading to economic losses and potential transmission of zoonotic diseases. Excessive use of antibiotics to treat these infections has resulted in antibiotic resistance. This study evaluates the antimicrobial effects of aqueous and ethanolic extracts of medicinal plants: Rosmarinus tournefortii, Cedrus atlantica, Juniperus oxycedrus, Allium sativum, and Ocimum basilicum against 13 pathogenic microorganisms, including strains affecting Tilapia: 2 strains of Staphylococcus aureus, Enterococcus faecalis, Bacillus cereus, Bacillus subtilis, Listeria monocytogenes, Escherichia coli, Enterobacter cloacae, Salmonella enteritidis, Klebsiella pneumoniae, Pseudomonas aeruginosa, and 2 strains of Candida albicans. Subsequently, plants exhibiting the best antimicrobial activity were selected for in vivo testing on Tilapia infected with P. aeruginosa. Results indicate that all tested plants possess antimicrobial activity against the tested microbial strains at varying concentrations. Garlic, however, showed no effect on the tested microorganisms. Generally, ethanolic extracts of all plants were more effective against the tested microorganisms at lower concentrations compared to aqueous extracts. Ethanolic extract of rosemary showed the lowest MIC values compared to extracts from other plants, while Atlas cedar's aqueous extract exhibited the lowest MIC values among the aqueous extracts. Regarding in vivo experimentation, juniper, Atlas cedar, and rosemary were selected and tested as anti-infective and immunostimulant agents for Tilapia infected with P. aeruginosa. Hematological analyses indicated that Atlas cedar and juniper induce better resistance to infection compared to rosemary.