Location: Warmwater Aquaculture Research UnitTitle: Edwardsiella piscicida identified in the southeastern United States by gyrB sequence, species specific and repetitive sequence mediated PCR Author
Submitted to: Diseases of Aquatic Organisms
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/16/2013
Publication Date: 2/4/2014
Citation: Griffin, M.J., Ware, C., Quiniou, S., Steadman, J., Gaunt, P., Khoo, L., Soto, E. 2014. Edwardsiella piscicida identified in the southeastern United States by gyrB sequence, species specific and repetitive sequence mediated PCR. Diseases of Aquatic Organisms. 108(1):23-35. Interpretive Summary: Edwardsiella tarda is a worldwide pathogen affecting both humans and aquatic animals. However it is known that the Edwardsiella tarda group is heterogenous and recent papers have identified a new taxa Edwardsiella piscicida among the Edwardsiella tarda group. A PCR assay was designed to distinguished between the different Edwardsiella and a survey of 44 archived bacterial specimens isolated from case submissions to the Aquatic Research and Diagnostic Laboratory in Stoneville, MS from 2007-2012 revealed that Edwardsiella piscicida was the most prevalent culprit in catfish aquaculture in the US.
Technical Abstract: A new taxa of Edwardsiella has recently been described from fishes of Europe and Asia. Researchers have determined this new strain does not belong to any established taxa within the genus Edwardsiella and have proposed the adoption of a new taxon, E. piscicida. A similar study in the United States also identified two genetically distinct taxa within the group of organisms traditionally classified as E. tarda. Comparisons of gyrB sequences between US isolates and isolates from Europe and Asia identified a group of US isolates homologous to the E. piscicida type strains, suggesting conspecificity. Using a newly developed discriminatory PCR, a survey was conducted of 44 archived bacterial specimens isolated from Mississippi farm-raised catfish from 2007-2012. Identified biochemically as E. tarda upon initial collection, all isolates were confirmed to be misclassified E. piscicida by PCR. In addition, repetitive sequence mediated PCR (rep-PCR) analysis of these archived bacterial specimens suggest a high degree of genetic homology. The gyrB sequence data, coupled with the E. piscicida specific-PCR and rep-PCR data, has confirmed E. piscicida from fish disease cases in the southeastern United States. Moreover, our data suggests E. piscicida is likely more prevalent in catfish aquaculture than E. tarda. This supports previous claims from Europe and Asia suggesting a cosmopolitan distribution of E. piscicida and a greater association with disease outbreaks in fish than E. tarda. To our knowledge, this is the first report of E. piscicida in the United States.