Abstract:
Tilapia (Oreochrornis niloticus) is one of the most abundant cultured species in
Malaysia. In fact, it is also listed as major farmed fish species in global aquaculture
production. However, the intensification of fish farming has been accompanied by
outbreak of many infectious diseases. Motile Aeromonad Septicaemia (MAS) caused by
Aeromonas hydrophila nas been reported as the most common bacteria disease that
affects aquaculture industry. This study was conducted to isolate and identify A.
hydrophila from a farm-raised tilapia in Terengganu, Malaysia. Thirteen isolates that
successfully isolated from intestine of tilapia fry were identified using conventional
method including morphological tests, biochemical tests and physiological tests. Result
revealed that l 00% of presumptive isolates were A. hydrophila and all isolates were
capable to produce a or p hemolysis in blood agar. The phenotypic relationships among
isolates were investigated using numerical taxonomy. Dice coefficient (So) was used to
compute the similarity between isolates. Finally, dendrogram was constructed using data
clustering method performed by Unweighted Pair Group Method with Arithmetic Mean
