Jantrakajorn S, Suyapoh W, Wongtavatchai J. Characterization of Lactococcus garvieae and Streptococcus agalactiae in cultured red tilapia Oreochromis sp. in Thailand.
J Aquat Anim Health 2024. [PMID:
38632692 DOI:
10.1002/aah.10217]
[Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/16/2023] [Revised: 01/04/2024] [Accepted: 02/20/2024] [Indexed: 04/19/2024]
Abstract
OBJECTIVE
Acute mortality with clinical symptoms of streptococcal-like infections was observed in red tilapia Oreochromis sp. cultured in floating cages in Prachin Buri Province, Thailand, during May 2023. Herein, we identified an emerging pathogen, Lactococcus garvieae, as the etiological agent.
METHODS
After bacterial isolation from the brain and kidney of diseased fish, identification was performed using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and the VITEK 2 system. Sequencing of the 16S ribosomal RNA (rRNA) gene and phylogenetic analysis were applied to confirm bacterial species. Antimicrobial susceptibility testing was conducted. Histopathological findings in the brain, kidney, spleen, liver, and heart were evaluated.
RESULT
From 20 fish samples, L. garvieae (n = 18 isolates) and Streptococcus agalactiae (n = 2 isolates) were identified. A phylogenetic tree of the 16S rRNA gene revealed that Thai isolates of either L. garvieae or S. agalactiae clustered with reference piscine isolates from intercontinental locations. Our isolates showed resistance against quinolones while being susceptible to other antimicrobials. Histopathological changes demonstrated severe septicemic conditions, with more invasive lesions-especially in the heart and liver-being apparent in L. garvieae-infected fish compared to S. agalactiae-infected fish.
CONCLUSION
This study represents the first reported outbreak of L. garvieae with a concurrent S. agalactiae infection in farmed red tilapia in Thailand.
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