Acta Veterinaria Hungarica 65 (1), pp. 50–59 (2017) DOI: 10.1556/004.2017.005 0236-6290/$ 20.00 © 2017 Akadémiai Kiadó, Budapest RAPID IDENTIFICATION OF PATHOGENIC STREPTOCOCCI ISOLATED FROM MORIBUND RED TILAPIA (OREOCHROMIS SPP.) Mohamed ABDELSALAM 1 , Mamdouh Y. ELGENDY 2 , Mohamed SHAALAN 3,4* , Mohamed MOUSTAFA 1 and Masayuki FUJINO 5 1 Department of Fish Diseases and Management, Faculty of Veterinary Medicine, Cairo University, Giza, Egypt; 2 Department of Hydrobiology, Veterinary Research Division, National Research Centre, Dokki, Giza, Egypt; 3 Department of Pathology, Faculty of Veterinary Medicine, Cairo University, Giza, Egypt; 4 Clinical Division of Fish Medicine, University of Veterinary Medicine, Veterinärplatz 1, A-1210 Vienna, Austria; 5 National Institute of Infectious Diseases, Tokyo, Japan (Received 14 August 2016; accepted 2 November 2016) Accurate and rapid identification of bacterial pathogens of fish is essential for the effective treatment and speedy control of infections. Massive mortalities in market-sized red tilapia (Oreochromis spp.) were noticed in mariculture concrete ponds in northern Egypt. Histopathological examination revealed marked conges- tion in the central vein of the liver with the presence of bacterial aggregates inside the lumen and in the vicinity of the central vein. A total of 12 isolates of strepto- cocci were obtained from the moribund fish. This study documented the ability of the MicroSeq 500 16S bacterial sequencing method to accurately identify Strepto- coccus agalactiae and S. dysgalactiae mixed infections from moribund red tilapia that were difficult to be recognised by the commercial biochemical systems. The continuously decreasing cost of the sequencing technique should encourage its application in routine diagnostic procedures. Key words: Streptococcus agalactiae, S. dysgalactiae, red tilapia, MicroSeq 500, histopathology Tilapia culture had been practised in Egypt via traditional methods for thousands of years as depicted by paintings on the walls of Egyptian tombs (Bar- dach et al., 1972). Egypt is now the second largest tilapia producer in the world, after China (Eltholth et al., 2015). The scarcity of freshwater resources and the competition with agriculture and other urban activities oriented the effort to- wards mariculture (Moustafa et al., 2015). Red tilapia is a promising species for mariculture due to its salinity tolerance (Romana-Eguia and Eguia, 1999). How- ever, the poor spawning performance of red tilapia and its vulnerability to infec- tious diseases are among the most significant constraints (Hulata et al., 1995). * Corresponding author; E-mail: Mohamed.Shaalan@vetmeduni.ac.at; Phone: 0043 (1) 250- 774-733