Phenotypic characterization and genetic diversity of Flavobacterium columnare isolated from red tilapia, Oreochromis sp., in Thailand

Abstract

Flavobacterium columnare is the aetiological agent of columnaris disease and severely affects various freshwater aquaculture fish species worldwide. The objectives of this study were to determine the phenotypic characteristics and genetic variability among F. columnare isolates isolated from red tilapia in Thailand. Forty-four F. columnare isolates were recovered from diseased fish in different geographical locations. The isolates exhibited homologous phenotypic characteristics but exhibited genetic diversity. One isolate was assigned to genomovar I, and the remainder were assigned to genomovar II, indicating the coexistence of these genomovars but predominance of genomovar II. Phylogenetic analysis of the 16S-23S ISR sequences revealed that a subset of the Thai isolates (n = 25) contained a smaller intergenic spacer region (ISR) (523-537 bp) and formed a unique ISR phylogenetic group. Phylogenetic analysis of the 16S rRNA gene supported the unique cluster of Thai isolates. This is the first description of the phenotypic and molecular characteristics of F. columnare isolated from red tilapia in Thailand as well as five isolates of F. columnare derived from other fish species including Nile tilapia, koi carp and striped catfish.

Naturally concurrent infections of bacterial and viral pathogens in disease outbreaks in cultured Nile tilapia (Oreochromis niloticus) farms

“…To identify taxonomic classification of the bacteria, NK01 to NK14 and NK-Fc01 to NK- and CUVET1214 isolated from red tilapia described in our previous study (Dong et al 2014) ( …”

Emergence of tilapia lake virus in Thailand and an alternative semi-nested RT-PCR for detection

“…Massive die-offs due to infectious diseases have brought huge economic losses not only to aquaculture producers but also to other related sectors. Among the identified fish killers of cultivated tilapia in Thailand, a significant number of emerging infectious pathogens have been reported during recent years, notably a novel genetic group of Flavobacterium columnare (Dong et al, 2015a), Francisella noatunensis subsp. orientalis Jantrakajorn and Wongtavatchai, 2016;Nguyen et al, 2016), Hahella chejuensis , Aeromonas jandaei and Aeromonas veronii (Dong et al, 2015b;Dong et al, 2017), betanodavirus (Keawcharoen et al, 2015), and infectious spleen and kidney necrosis virus (ISKNV/Iridovirus) (Dong et al, 2015b;Suebsing et al, 2016).…”

Serotype distribution and antimicrobial susceptibilities of Streptococcus agalactiae isolated from infected cultured tilapia (Oreochromis niloticus) in Thailand: Nine-year perspective

“…The major pathogenic bacteria responsible for mortalities in tilapia include Aeromonas hydrophila (Tipmongkolsilp et al, 2012), Francisella noatunensis subsp. orientalis (Soto et al, 2013), Flavobacterium columnare (Dong et al, 2015), Vibrio vulnificus (Chen et al, 2006), Streptococcus iniae (Suanyuk et al, 2010) and Streptococcus agalactiae (group B Streptococcus, GBS) (Suanyuk et al, 2008).…”