Fish play a crucial role in the Bangladeshi diet, providing more than 60% of animal source food, representing a crucial source of micro-nutrients, and possessing an extremely strong cultural attachment. In this study isolation and identification of Aeromionas hydrophila was done by studying cultural properties, gram staining and biochemical properties of isolates of Shing fish (Heteropneustes fossilis) of different upazillas of Mymensingh district. Antibiogram profile of the isolated bacteria was studied by using wide range of commercially available antibiotics. Quantitative study of bacteria isolated from diseased Shing fish showed variation of number in different organ. Total bacterial load was found to be 1.90 × 10⁵, 1.19 × 10⁵, 3.21 × 10⁵, 2.18 × 10⁶ and 3.14 × 10⁵cfu/g in lesions; 2.52 × 10⁷, 2.34 × 10⁸, 5.41 × 10⁸, 2.54 × 10⁹ and 5.21 × 10⁹cfu/g in liver; 2.54 × 10⁸, 2.41 × 10⁸, 1.90 × 10⁷, 3.65 × 10⁷ and 3.45 × 10⁸cfu/g in spleen; 3.51 × 10⁷, 5.28 × 10⁷, 3.14 × 10⁶, 1.85 × 10⁷ and 4.52× 10⁷cfu/g in kidney in diseased Shing of Mymensingh sadar, Muktagacha, Tarakanda, Gouripur and Fulpurupazillas, respectively under Mymensingh districts. Aeromonas hydrophila was initially identified by their specific morphological, physiological and biochemical characteristics. Then molecular detection of A. hydrophila was done by PCR. PCR products of desired 760 bp were obtained for A. hydrophila. The results of the antibiotic sensitivity test is exhibited that most of the bacterial samples were sensitive against ciprofloxacin (92%) and levofloxacin (84%), intermediate resistant against gentamicin (40%) and resistant against novobiocin (84%), ampicillin (100%) and penicillin (92%).