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Development of a quantitative PCR assay for monitoring Streptococcus agalactiae colonization and tissue tropism in experimentally infected tilapia
Author(s) -
Su YL,
Feng J,
Li YW,
Bai JS,
Li AX
Publication year - 2016
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.12358
Subject(s) - biology , streptococcus agalactiae , oreochromis , microbiology and biotechnology , tissue tropism , tropism , polymerase chain reaction , real time polymerase chain reaction , 16s ribosomal rna , tilapia , virulence , colonization , bacteria , virology , streptococcus , fish <actinopterygii> , virus , gene , fishery , biochemistry , genetics
Streptococcus agalactiae has become one of the most important emerging pathogens in the aquaculture industry and has resulted in large economic losses for tilapia farms in China. In this study, three pairs of specific primers were designed and tested for their specificities and sensitivities in quantitative real‐time polymerase chain reactions ( qPCR s) after optimization of the annealing temperature. The primer pair IGS ‐s/ IGS ‐a, which targets the 16S‐23S rRNA intergenic spacer region, was finally chosen, having a detection limit of 8.6 copies of S. agalactiae DNA in a 20 μL reaction mixture. Bacterial tissue tropism was demonstrated by qPCR in Oreochromis niloticus 5 days post‐injection with a virulent S. agalactiae strain. Bacterial loads were detected at the highest level in brain, followed by moderately high levels in kidney, heart, spleen, intestines, and eye. Significantly lower bacterial loads were observed in muscle, gill and liver. In addition, significantly lower bacterial loads were observed in the brain of convalescent O. niloticus 14 days post‐injection with several different S. agalactiae strains. The qPCR for the detection of S. agalactiae developed in this study provides a quantitative tool for investigating bacterial tissue tropism in infected fish, as well as for monitoring bacterial colonization in convalescent fish.