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Isolation and Pathogenicity of Streptococcus iniae in Cultured Red Hybrid Tilapia in Malaysia
Author(s) -
Rahmatullah M.,
Ariff M.,
Kahieshesfandiari M.,
Daud H. M.,
ZamriSaad M.,
Sabri M. Y.,
Amal M. N. A.,
InaSalwany M. Y.
Publication year - 2017
Publication title -
journal of aquatic animal health
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.507
H-Index - 52
eISSN - 1548-8667
pISSN - 0899-7659
DOI - 10.1080/08997659.2017.1360411
Subject(s) - streptococcus iniae , biology , tilapia , microbiology and biotechnology , oreochromis , aeromonas veronii , nile tilapia , oreochromis mossambicus , veterinary medicine , aeromonas , bacteria , immunology , fishery , immune system , fish <actinopterygii> , medicine , genetics
This study describes the isolation and pathogenicity of Streptococcus iniae in cultured red hybrid tilapia (Nile Tilapia Oreochromis niloticus × Mozambique Tilapia O. mossambicus ) in Malaysia. The isolated gram‐positive S. iniae appeared punctiform, transparently white, catalase and oxidase negative and produced complete β‐hemolysis on blood agar, while a PCR assay resulted in the amplification of the 16 S rRNA gene and lactate oxidase encoded genes. The isolate was sensitive to tetracycline, vancomycin, and bacitracin but was resistant to streptomycin, ampicillin, penicillin, and erythromycin. Pathogenicity trials conducted in local red hybrid tilapia (mean ± SE = 20.00 ± 0.45 g) showed 90.0, 96.7, and 100.0% mortality within 14 d postinfection following intraperitoneal exposure to 10 4 , 10 6 , and 10 8 CFU/mL of the pathogen, respectively. The clinical signs included erratic swimming, lethargy, and inappetance at 6 h postinfection, while mortality was recorded at less than 24 h postinfection in all infected groups. The LD 50‐336 h of S. iniae against the red hybrid tilapia was 10 2 CFU/mL. The post mortem examinations revealed congested livers, kidneys, and spleens of the infected fish. This is the first report of S. iniae experimental infection in cultured red hybrid tilapia in Malaysia. Received January 20, 2017; accepted July 16, 2017 Published online October 11, 2017