ARTICLE INFO

ABSTRACT

Received date: 29/07/2015

Accepted date: 19/02/2016

Streptococcus iniae, as a cause of Streptococcosis outbreak of cultured tilapia, is a hemolytic and Gram-positive bacterium. In this study, a one-step PCR method was developed for the detection of S. iniae from fish kidney. The oligonucleotide primers, assigned as LOX-1 and LOX-2, are designed from lactate oxidase gene of S. iniae. Using extracted DNA from bacterial cells or head kidney of S. iniae infected fish, the PCR reaction yields a 870 bp fragment specific to the S. iniae. Primers LOX-1 and LOX-2 did not amplify DNA from other common bacteria in cultured fish (Streptococcus agalactiae, Aeromonas hydrophila, Edwardsiella ictaluri, and Vibrio harveyi). The detection limit of this primer pair is 10² CFU/mL of S. iniae. The improved one-step PCR method provides a diagnostic tool for: (i) the detection of S. iniae directly from infected fish tissue; (ii) and the identification of S. iniae from bacteria cells.

KEYWORDS

PCR, red tilapia, Streptococcus iniae, tissue