Jornal de Microbiologia e Patologia

Screening of Herbs and Spices for Antimicrobial Properties against Flavobacterium columnare

Abstract

Grace Ramena, Yathish Ramena, William Duke and Nitin Challa

Bacterial diseases like columnaris caused by Flavobacterium columnare, result in huge economic loss to aquaculture farmers. Although there are commercially available vaccines and antibiotics to control bacterial diseases, they are proven to be inefficient. Moreover, antibiotics lead to acquired resistance in bacteria, and the drug residual in fish, resulting in tight regulations for their usage. This calls for new alternative solutions that can be safe and cost-effective to prevent and treat fish diseases. Plant extracts are well known for their anti-microbial properties and they could be potential alternative candidates. Usage of plant extracts as therapeutics is largely used for human pathologies but there is limited knowledge for the same to treat piscine disease. We have evaluated the anti-microbial properties of extracts from eleven herbs and spices and compared their antimicrobial effect with commercially available antibiotic Oxytetracycline (Terramycin® 200), that is used to treat columnaris. We found that all the extracts (50 mg/ml) we have tested, had bactericidal effects against Flavobacterium columnare (3 × 10⁸ CFU/ml). Interestingly, Syzygium aromaticum, Cuminum cyminum and Thymus vulgaris showed highest antimicrobial activity against Flavobacterium columnare with an average inhibition of 20 mm and Cinnamomum verum showed 18 mm, which is similar to Oxytetracycline (30 μg). We speculate that the extracts we have identified could serve as potential alternative therapeutics to treat columnaris in fish that would have fewer or no regulations and be cost-effective.