The parasitic infestation in the commercially important fish Clariusbatrachuswas investigated. The study based on examination of Clariasbatrachus under aseptic conditions collected from a commercial farm from Punalur, Kollam, Kerala revealed the bacterial parasite of the catfish to be fairly rich comprising Aeromonashydrophila. The gut region samples were serially diluted, incubated and plated.The edited sequence (16 S rRNA sequence) were then used for similarity searches using BLAST (Basic Local Alignment Search Tool) program in the NCBI Genbank DNA database for identifying the sample. The 16S rRNA gene was identical and exhibited 100% sequence similarity with the other known isolates of A. hydrophila available in the GenBank. Aeromonashydrophila is a heterotrophic, Gram-negative, rod-shaped bacterium mainly found in areas with a warm climate. This bacterium can be found in fresh or brackish water. It can survive in aerobic and anaerobic environments, and can digest materials such as gelatinand hemoglobin. A.hydrophila was isolated from humans and animals in the 1950s. It is the most well-known of the species of Aeromonas. In this paper, we reported the isolation and molecular detection of A. hydrophilafrom a Clariusbatrachus.
