Genetic variability of Edwardsiella piscicida isolates from Mississippi catfish aquaculture with an assessment of virulence in channel and channel × blue hybrid catfish

The bacterium Edwardsiella piscicida causes significant losses in global aquaculture, particularly channel (Ictalurus punctatus) × blue (I. furcatus) hybrid catfish cultured in the south‐eastern United States. Emergence of E. piscicida in hybrid catfish is worrisome given current industry trends tow...

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Bibliographic Details
Published in:Journal of fish diseases 2021-11, Vol.44 (11), p.1725-1751
Main Authors: López‐Porras, Adrián, Griffin, Matt J., Armwood, Abigail R., Camus, Alvin C., Waldbieser, Geoffrey C., Ware, Cynthia, Richardson, Bradley, Greenway, Terrence E., Rosser, Thomas Graham, Aarattuthodiyil, Suja, Wise, David J.
Format: Article
Language:English
Subjects:
Aquaculture
Catfish
Edwardsiella piscicida
edwardsiellosis
Fingerlings
Freshwater fishes
Genes
Genetic diversity
Genetic variability
Genetic variance
hybrid catfish
Ictalurus punctatus
Mortality
multilocus sequence analysis
Nucleotide sequence
PCR
Primers
rep‐PCR
Sequence analysis
Sequencing
Variability
Virulence
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Summary:The bacterium Edwardsiella piscicida causes significant losses in global aquaculture, particularly channel (Ictalurus punctatus) × blue (I. furcatus) hybrid catfish cultured in the south‐eastern United States. Emergence of E. piscicida in hybrid catfish is worrisome given current industry trends towards increased hybrid production. The project objectives were to assess intraspecific genetic variability of E. piscicida isolates recovered from diseased channel and hybrid catfish in Mississippi; and determine virulence associations among genetic variants. Repetitive extragenic palindromic sequence‐based PCR (rep‐PCR) using ERIC I and II primers was used to screen 158 E. piscicida diagnostic case isolates. A subsample of 39 E. piscicida isolates, representing predominant rep‐PCR profiles, was further characterized using BOX and (GTG)5 rep‐PCR primers, virulence gene assessment and multilocus sequence analysis (MLSA) targeting housekeeping genes gyrb, pgi and phoU. The MLSA provided greater resolution than rep‐PCR, revealing 5 discrete phylogroups that correlated similarly with virulence gene profiles. Virulence assessments using E. piscicida representatives from each MLSA group resulted in 14‐day cumulative mortality ranging from 22% to 54% and 63 to 72% in channel and hybrid fingerlings, respectively. Across all phylogroups, mortality was higher in hybrid catfish (p 
ISSN:0140-7775
1365-2761
DOI:10.1111/jfd.13491