Antimicrobial Efficacy of Garlic ( Allium sativum ) Extract Against Aeromonas Hydrophila Isolated From Diseased Pangasius Catfish

Background Pangasius catfish ( Pangasianodon hypophthalmus ) is one of the most commercially and nutritionally valuable aquaculture species in Bangladesh. In recent years, outbreaks of bacterial diseases, particularly those caused by Aeromonas hydrophila , have posed serious challenges to its production. The frequent and often indiscriminate use of antibiotics for disease management has intensified the problem of antimicrobial resistance, emphasising the urgent need for safe, effective and sustainable alternatives. Objectives This study assessed the antibacterial potential of garlic ( Allium sativum ) extracts against A. hydrophila isolated from infected Pangasius catfish. Methods A total of 49 bacterial isolates were collected from different commercial Pangas fish farms located in Trishal, Muktagacha and Phulpur upazilas of Bangladesh. All isolates were molecularly confirmed as A. hydrophila . The antibacterial activity of aqueous and methanolic garlic extracts was subsequently evaluated using disc diffusion, minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) assays. Results The aqueous extract exhibited no detectable antibacterial activity, whereas the methanolic extract demonstrated marked inhibitory effects against A. hydrophila . The largest inhibition zone (15.11 ± 0.05 mm) was observed at 8 mg/mL of garlic extract in 20% methanol. MIC values ranged between 6 and 8 mg/mL, while MBC assays confirmed bactericidal activity at 8 mg/mL in 20% methanol. These findings indicate that the methanolic extract exhibited significant antibacterial properties and could be recommended as a phytobiotic alternative to antibiotics for managing A. hydrophila infections in Pangasius aquaculture. Conclusion Methanolic extracts of garlic exhibit significant antibacterial activity against A. hydrophila and could be recommended as a phytobiotic alternative to conventional antibiotics for managing A. hydrophila infections in Pangasius aquaculture. This natural approach may contribute to sustainable fish health management and mitigate the development of antimicrobial resistance.