The study was carried out from November, 2014 to February, 2015 with the objective of isolating Aeromonas hydrophila an important fish pathogen from infected air-breathing catfish Magur (Clarias batrachus) in Mymensingh district. Quantitative study of the isolated bacteria from infected C. batrachus was found variation of number in different organs. Total bacterial load was found to be 1.16 x 105 to 3.15 x 106 cfu/g in lesions, 2.14 x 108 to 4.17 x 109 cfu/g in liver, 1.90 x 107 to 5.12 x 108 cfu/g in spleen and 2.32 x 106 to 5.24 x 108 cfu/g in kidney of infected C. batrachus in Mymensingh district. The isolates were found to produce acid from arabinose, whereas acid and gas from different sugar media such as maltose, sucrose, and dextrose. Morover, they were capable to ferment glucose but resistant to vibriostatic agent 0129 test. Further identification of A. hydrophila was accomplished using PCR. The PCR products of desired 760 bp were obtained for A. hydrophila. The isolated A. hydrophila were 96% sensitive to Enrofloxacin followed by 88% to Ciprofloxacin and 76% to Levofloxacin. On the other way, 100% were resistant to the Ampicillin followed by 96% to Penicillin and 92% to Novobiocin. So far, this is the first molecular identification of A. hydrophila from farmed C. batrachus in Bangladesh. The present study will provide future research scopes on identification of pathogenicity island in chromosome and serotyping of all A. hydrophila isolates. Asian Australas. J. Food Saf. Secur. 2017, 1 (1), 17-24

The present study was carried out to evaluate the comparative capability of producing infections and causing mortality of the experimental Magur (Clarias batrachus) with motile Aeromonas species. A total of 200 apparently healthy C. batrachus were acclimatized to the laboratory conditions for experimental study. Nine different groups (each group consisting of 20 fish) of healthy C. batrachus was injected with nine motile Aeromonas isolates (A. hydrophila-3, A. sobria-3 and A. caviae-3). Experimental C. batrachus were infected with motile A. hydrophila, A. sobria and A. caviae to groups 1-3, 4-6 and 7-9, respectively while group 10 was injected with sterile physiological saline (0.85% NaCl) and served as the control. The selected motile bacterial species via intramuscularly were injected at the rate of 4.5 × 105 cfu/fish for pathogenicity study on C. batrachus and monitored up to two weeks. The highest clinical infections were noticed 90% in group-3 whereas only 35% in group-8 within the experimental period. After two weeks of the experiment, the cumulative mortality rate was also found highest (60%) in group-3 but lowest (15%) in group-9 while no infection or mortality showed in group-10 (control group). The development of infection and mortality to the injected C. batrachus was associated more severely by Aeromonas hydrophila than A. sobria and A. caviae used in this study. However, the isolates motile Aeromonas species could serve as the primary cause of skin lesions as well as mortality in cultured C. batrachus. Asian Australas. J. Food Saf. Secur. 2017, 1 (1), 45-50

Stinging catfish, Shing (Heteropneustes fossilis) is been cultured in Bangladesh which is one of the most popular and highly valuable fish species. A total of 120 diseased H. fossilis were collected from twenty five fish farms in greater Mymensingh region, Bangladesh between November 2013 to February 2014. Remarkable clinical symptoms of the affected fishes were loss of equilibrium and, erosions at the bases of fins and tail, hemorrhages and skin lesions on body surface, profuse mucous secretion and congestion along with enlargement of most of the internal organs. Three different kinds of selective media were used for the isolation of total population of bacteria from the affected fishes. A number of biochemical tests were performed for the identification of the isolated bacteria. Commercially available panel of antibiotics were used for the determination of sensitivity of the isolated bacteria. A total of 85 bacterial strains were isolated and the isolated were Aeromonas hydrophila, A. salmonicida, A. sobria, Pseudomonas angulliseptica, P. fluorescens and Vibrio anguillarum. Aeromonas spp. appeared to be the main pathogen in the diseased fishes. Among the isolated spp of bacteria distribution of Aeromonas species was as follows: A. hydrophila 34 (40.00%), A. salmonicida 14 (16.47%), A. sobria 8 (9.41%) as well as 5 (5.88%) unidentified Aeromons strains. The other isolated of  Pseudomonas anguliseptica, P. fluorescens, Vibrio anguillarum and Vibrio spp were distributed as 12 (14.11%), 4 (4.70%), 3 (3.52%) and 5 (5.88%), respectively in infected H. fossilis. However, results of antibiotic sensitivity test revealed that all the bacterial isolates of H. fossilis were found more or less resistant to all most all the antibiotics with the exception of ciprofloxacin and levofloxacinn which were found highly sensitivity against all the strains of Aeromonass pp. and other species of bacteria. Asian Australas. J. Biosci. Biotechnol. 2016, 1 (1), 116-124