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First identification and characterization of Streptococcus iniae obtained from tilapia ( Oreochromis aureus ) farmed in Mexico
Author(s) -
Ortega C,
García I,
Irgang R,
Fajardo R,
TapiaCammas D,
Acosta J,
AvendañoHerrera R
Publication year - 2018
Publication title -
journal of fish diseases
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.819
H-Index - 85
eISSN - 1365-2761
pISSN - 0140-7775
DOI - 10.1111/jfd.12775
Subject(s) - streptococcus iniae , biology , rainbow trout , tilapia , oreochromis , aquaculture , danio , microbiology and biotechnology , zebrafish , oreochromis mossambicus , 16s ribosomal rna , aquatic animal , veterinary medicine , fish farming , trout , fishery , fish <actinopterygii> , bacteria , genetics , gene , medicine
This is the first study to isolate, identify and characterize Streptococcus iniae as the causative disease agent in two tilapia ( Oreochromis aureus ) populations. The populations were geographically isolated, of distinct origins, and did not share water sources. Affected fish showed various external (e.g., exophthalmia and cachexia, among others) and internal (e.g., granulomatous septicaemia and interstitial nephritis, among others) signs. All internal organ samples produced pure cultures, two of which (one from each farm, termed S‐1 and S‐2) were subjected to biochemical, PCR and 16S rRNA sequencing (99.5% similarity) analyses, confirming S. iniae identification. The two isolates presented genetic homogeneity regardless of technique (i.e., RAPD , REP ‐ PCR and ERIC ‐ PCR analyses). Pathogenic potentials were assessed through intraperitoneal injection challenges in rainbow trout ( Oncorhynchus mykiss ) and zebrafish ( Danio rerio ). Rainbow trout mortalities were respectively 40% and 70% at 10 4 and 10 6 CFU per fish with the S‐1 isolate, while 100% mortality rates were recorded in zebrafish at 10 2 and 10 4 CFU per fish with the S‐2 isolate. The obtained data clearly indicate a relationship between intensified aquaculture activities in Mexico and new disease appearances. Future studies should establish clinical significances for the tilapia industry.