Multilocus Variable-Number Tandem-Repeat Analysis of Yersinia ruckeri Confirms the Existence of Host Specificity, Geographic Endemism, and Anthropogenic Dissemination of Virulent Clones

• Published in: Applied and Environmental Microbiology
• Main Authors: Gulla, Snorre, Barnes, Andrew C, Welch, Timothy J, Romalde, Jesús L, Ryder, David, Ormsby, Michael J, Carson, Jeremy, Lagesen, Karin, Verner-Jeffreys, David W, Davies, Robert L, Colquhoun, Duncan J
• Other Authors: The Norwegian Seafood Research Fund, Norwegian Veterinary Institute, University of Queensland, USDA – Agricultural Research Service, USA, University of Santiago de Compostela (USC), CEFAS - Centre for Environment, Fisheries and Aquaculture Science, University of Glasgow, Tasmanian Department of Primary Industries, Parks, Water and Environment, orcid:0000-0002-3991-2336
• Format: Article in Journal/Newspaper
• Language: English
• Published: American Society for Microbiology 2018
• Subjects: Atlantic salmon; MLST; MLVA; Yersinia ruckeri; fish pathogen; geographic endemism; host specificity; molecular typing; rainbow trout; yersiniosis
• Online Access: http://hdl.handle.net/1893/33657; https://doi.org/10.1128/AEM.00730-18; http://dspace.stir.ac.uk/retrieve/1ba01df1-c5c8-41c7-94b9-8cbf597faddd/AEM.00730-18.pdf

This comprehensive population study substantially improves our understanding of the epizootiological history and nature of an internationally important fish-pathogenic bacterium. The MLVA assay developed and presented represents a high-resolution typing tool particularly well suited for Yersinia ruckeri infection tracing, selection of strains for vaccine inclusion, and risk assessment. The ability of the assay to separate isolates into geographically linked and/or possibly host-specific clusters reflects its potential utility for maintenance of national biosecurity. The MLVA is internationally applicable and robust, and it provides clear, unambiguous, and easily interpreted results. Typing is reasonably inexpensive, with a moderate technological requirement, and may be completed from a harvested colony within a single working day. As the resulting MLVA profiles are readily portable, any Y. ruckeri strain may rapidly be placed in a global epizootiological context. A multilocus variable-number tandem-repeat analysis (MLVA) assay was developed for epizootiological study of the internationally significant fish pathogen Yersinia ruckeri , which causes yersiniosis in salmonids. The assay involves amplification of 10 variable-number tandem-repeat (VNTR) loci in two five-plex PCRs, followed by capillary electrophoresis. A collection of 484 Y. ruckeri isolates, originating from various biological sources and collected from four continents over 7 decades, was analyzed. Minimum-spanning-tree cluster analysis of MLVA profiles separated the studied population into nine major clonal complexes and a number of minor clusters and singletons. The major clonal complexes could be associated with host species, geographic origin, and serotype. A single large clonal complex of serotype O1 isolates dominating the yersiniosis situation in international rainbow trout farming suggests anthropogenic spread of this clone, possibly related to transport of fish. Moreover, subclustering within this clonal complex indicates putative ...