Isolation and identification of Streptococcus spp. isolated from red tilapia (Oreochromis niloticus)

Abstract

Streptococcus spp. is one of the most significant diseases in tilapia culture worldwide and particularly in indoor system. Streptococcus spp. is the largest problem in intensive tilapia rearing systems throughout the world. Streptococcal infections in fish result in septicemic diseases that have been reported worldwide causing severe economic losses in fish production. This study was conducted to isolate and identify the Streptococcus spp. from red tilapia (Oreochromis niloticus). In this present study, a total of 127 red tilapias ( Oreochromis niloticus) were caught in tilapia cage culture in Sungai Manir (Terengganu), Sungai Arau (Perlis), Sungai Kodiang (Kedah), Sungai Tunjang (Kedah) and Aquaculture Development Centre, Jitra, Kedah. The fishes then were dissected and the organs of brain, eye and kidney were streaked directly on Blood Agar (Merck, Germany) containing 5% of human blood. The bacterial colonies then were subcultured on TSA media (Merck, Germany) to get the pure colony. The gram staining process was carried out to all isolates and only five out of 127 isolates turned out to be positive. Out of these, only three isolates showed negative result for catalase test.