Isolation and Identification of Aeromonas hydrophila from Carps, Catfishes, Perches, and an Eel from Mymensingh Region of Bangladesh

Aeromonas hydrophila is a causative agent of MAS (Motile Aeromonas Septicemia) disease, causing huge mortality of fish all over the country. Isolation and identification of this bacteria, A. hydrophila from eight infected fish species: catla (Catla catla), rui (Labeo rohita), mrigal (Cirrhina cirrhosus), tarabaim (Macrognathus aculeatus), tilapia (Tilapia mossambicus), shing (Heteropneustes fossilis), koi (Anabas testudineus), and magur (Clarias batrachus) were undertaken from Tarakanda and Trishal upazila of Mymensingh District of Bangladesh. Fishes showed pale body color, external hemorrhages, reddish head, and reddish anal region. The intestine, kidney, and liver of each fish were inoculated over the AIM (Aeromonas Isolation Medium) and TSA (Tryptone Soya Agar) plates. The colonies of the first plates (AIM) were used for characterizing Aeromonas and the colonies of TSA plates were used for quantitative study. TSA plates showed the minimum bacterial load was 1.20 × 10² CFU/g in the kidney of tilapia and a maximum of 8.70 × 10⁶ CFU/g in the intestine of catla. Isolated bacteria were finally identified as Aeromonas hydrophila by their physiological, biochemical, and morphological characteristics. They were rod-shaped, gram-negative, and motile. The bacteria showed positive reactions for catalase, oxidase, fermented glucose, and were resistant to vibriostatic agent 0129. A shortcut method of identifying A. hydrophila has been developed by this work. Thus, the bacteria as well as MAS disease can be detected easily, and our fish culturists will be able to save their cultured fish by using any recognized anti-Aeromonas drug.

Keywords: Pathogenic bacteria; Aeromonas hydrophila; Carps; Catfishes; Perches; Eel; Motile Aeromonas Septicemia.