3 years ago

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.

Arias, Welch, Waldbieser, LaFrentz, Gaunt, Cipriano, Reichley, Steadman, Wise, Griffin, Stine, Ware, Greenway, Thachil, Lawrence, García, Khoo, Loch
Edwardsiella spp. are responsible for significant losses in important wild and cultured fish species worldwide. Recent phylogenomic investigations have determined bacteria historically classified as E. tarda actually represent three genetically distinct, yet phenotypically ambiguous taxa with varying degrees of pathogenicity in different hosts. Previous recognition of these taxa was hampered by the lack of a distinguishing phenotypic character. Commercial test panel configurations are relatively constant over time, and as new species are defined, appropriate discriminatory tests may not be present in current test panel arrangements. While phenobiochemical tests fail to discriminate between these taxa, data presented herein revealed discriminatory peaks for each Edwardsiella spp. using MALDI-TOF methodology, suggesting MALDI-TOF can offer rapid, reliable identification in line with current systematic classifications. Furthermore, a multiplex PCR assay was validated for rapid molecular differentiation of the Edwardsiella affecting fish. Moreover, the limitations of relying on partial 16S rRNA for discrimination of the Edwardsdiella and advantages of employing alternative single copy genes gyrB and sodB for molecular identification and classification of the Edwardsiella were demonstrated. Lastly, sodB sequencing confirmed isolates previously defined as typical, motile, fish pathogenic E. tarda are synonymous with E. piscicida; while atypical, non-motile fish pathogenic E. tarda are equivalent to E. anguillarum Fish non-pathogenic E. tarda are consistent with E. tarda as it is currently defined. These analyses help deconvolute the scientific literature regarding these organisms and provide baseline information to better facilitate proper taxonomic assignment and minimize erroneous identifications of Edwardsiella isolates in clinical and research settings.

Publisher URL: http://doi.org/10.1128/JCM.00970-17

DOI: 10.1128/JCM.00970-17

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