Identification of Vagococcus salmoninarum from rainbow trout (Oncorhynchus mykiss Walbaum, 1792) using proteomics–based MALDI–TOF MS

Vagococcus salmoninarum is a pathogen causing vagococcosis in rainbow trout (Oncorhynchus mykiss, Walbaum 1792) broodstock and large fish. In this study, conventional diagnostic methods, including phenotypic, genomic and high throughput proteomic MALDI‐TOF MS were tested together for accurate and rapid identification of V. salmoninarum. Twelve isolates from extensively infected internal organs (fins, gills, liver, heart and kidney) of a total of fifty fish were phenotypically confirmed as V. salmoninarum by biochemical–enzymatic characteristics using the BBL Crystal™ GP identification system. However, the presence of positive PCR amplification of 16S rDNA gene was detected only in 83% of these isolates and the same samples were identified as V. salmoninarum by MALDI–TOF MS method with high mass score value (m/z) between 2.00 and 3.00. Based on the comparative data obtained in this study, we conclude that the MALDI–TOF MS method is the most promising and recommended method for the definitive identification of V. salmoninarum.