Antimicrobial activity of twelve plant-derived compounds against fish-associated non-tuberculous mycobacteria

Nontuberculous mycobacteria (NTM) are important pathogens of fish, causing chronic infections that are difficult to control in aquaculture. In this study, we evaluated the in vitro antimicrobial activity of twelve plant-derived compounds against six fish-associated NTM strains using a broth microdilution assay. Minimum inhibitory concentrations (MICs) ranged from 0.25 to >32 µg/mL. Our results demonstrated that cinnamaldehyde exhibited the strongest antimycobacterial effect, followed by sesamol and farnesol, while several other phytochemicals showed moderate activity and salicylic acid was inactive. These findings highlight the potential of selected plant-derived compounds, particularly cinnamaldehyde, as promising candidates for alternative or adjunctive strategies against fish mycobacteriosis.