Location: Warmwater Aquaculture Research UnitTitle: Comparative phenotypic and genotypic analysis of Edwardsiella spp. isolates from different hosts and geographic origins, with an emphasis on isolates formerly classified as E. tarda and an evaluation of diagnostic methods
|REICHLEY, STEPHEN - Mississippi State University|
|WARE, CYNTHIA - Mississippi State University|
|STEADMAN, JAMES - Mississippi State University|
|GAUNT, PATRICIA - Mississippi State University|
|THACHIL, ANIL - Cornell University|
|STINE, CYNTHIA - Food And Drug Administration(FDA)|
|Waldbieser, Geoffrey - Geoff|
|ARIAS, COVA - Auburn University|
|LOCK, THOMAS - Michigan State University|
|Welch, Timothy - Tim|
|CIPRIANO, ROCCO - Us Geological Survey (USGS)|
|GREENWAY, TERRENCE - Mississippi State University|
|KHOO, LESTER - Mississippi State University|
|WISE, DAVID - Mississippi State University|
|LAWRENCE, MARK - Mississippi State University|
|GRIFFIN, MATT - Mississippi State University|
Submitted to: Journal of Clinical Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/28/2017
Publication Date: 10/4/2017
Citation: Reichley, S.R., Ware, C., Steadman, J., Gaunt, P.S., Garcia, J.C., LaFrentz, B.R., Thachil, A., Stine, C.B., Waldbieser, G.C., Arias, C.R., Lock, T., Welch, T.J., Cipriano, R.C., Greenway, T.E., Khoo, L.H., Wise, D.J., Lawrence, M.L., Griffin, M.J. 2017. Comparative phenotypic and genotypic analysis of Edwardsiella spp. isolates from different hosts and geographic origins, with an emphasis on isolates formerly classified as E. tarda and an evaluation of diagnostic methods. Journal of Clinical Microbiology. 55:3466-3491.
Interpretive Summary: Bacteria from the genus Edwardsiella can cause significant economic losses to commercial catfish production. Therapeutic treatments depend on accurate clinical diagnosis but traditional diagnostic tests did not sufficiently differentiate all Edwardsiella species. Researchers at Mississippi State University, USDA-Agricultural Research Service, and five other institutions tested 47 isolates of Edwardsiella species for identify methods useful in diagnostic labs to differentiate the five Edwardsiella species (E. ictaluri, E. tarda, E. piscicida, E. anguillarum, and E. hoshinae). The team found no biochemical methods that would differentiate all five species, but DNA sequencing of the sodB and gyrase B genes could provide individual species identification. Matrix assisted laser desorption ionization time-of-flight technology was also capable of differentiating all five species. Sequencing of the 16S ribosomal RNA genes, a technique commonly used to identify species, was not sufficient to differentiate the Edwardsiella species. These diagnostic tests will be essential for accurate clinical diagnoses in diseased catfish.
Technical Abstract: Aims: Conventional phenotypic and genotypic analyses for the differentiation of phenotypically ambiguous Edwardsiella congeners was evaluated and historical E. tarda designations were linked to current taxonomic nomenclature. Methods and Results: Forty-seven Edwardsiella spp. isolates recovered over 47 years from 10 countries and 19 host species were analyzed using four commercial microbial identification systems. Matrix assisted laser desorption ionization time-of-flight technology and fatty acid methyl ester analysis was conducted and antimicrobial susceptibility profiles were generated. Phylogenetic analysis using 3 reference genes, genetic fingerprinting and plasmid profiling was performed. Lastly, a multiplex real-time PCR assay (mPCR) was validated for all Edwardsiella spp. affecting fish, affording identification in a single reaction. Conclusion: Microbial identification databases require updating to remain consistent with contemporary systematics. MALDI-TOF can distinguish the five Edwardsiella spp. 16S rRNA has limited utility for the Edwardsiella, while the single copy markers gyrB and sodB provide adequate resolution for species identification. Significance and Impact of the Study: This study identified discrete MALDI-TOF profiles for each Edwardsiella spp., while validating an mPCR assay to quickly distinguish amongst Edwardsiella spp. affecting fish. Furthermore, genetic sequence data linked E. tarda, E. piscicida and E. anguillarum to historical records of isolates previously classified as E. tarda.