This study was conducted to isolate and characterize the bacteriophages capable of lysing Aeromonas hydrophila causing hemorrhagic septicemia in striped catfish (Pangasianodon hypophthalmus). The isolation and characterization were conducted in various samples of water, sludge, intestines and kidneys of animal. It was shown that, a total of 64 bacteriophages (58.2%) were isolated from 110 samples, with the highest value being from sludge samples (100%). When phages were tested in different pH levels (2-10), the above 64 phages were well adjusted to the pH 5-8 after 24 hours at 28oC, representing a rate of more than 60%. In addition, in one hour, 50% of the phages could survive at different temperatures (4^oC, 20^oC, 60^oC, 80^oC, 100^oC, and 120^oC) with no effects on phages observed at 4^oC and 20^oC. From the pH and temperature tests, six phages (B.N26, B.N16, B.R18, B.B8, B.R22, and B.N1) were selected to evaluate the lysis capacity against A. hydrophila in tap and river water for 21 days in vitro. The results revealed that the bacteriophages could survive better in river water than in tap water. All six phages could be utilized to investigate the effectiveness of treating A. hydrophila-caused hemorrhagic disease in catfish in vivo.

Keywords: Aeromonas hydrophila; Bacteriophage; Isolation; pH; Striped Catfish; Temperature