Rapid identification of Vibrio species belonging to the Harveyi clade by MALDI-TOF MS profiling using main spectral profile database implemented with an in-house database: Luvibase. Luvibase

Vibrio bacteria, such as members of the Harveyi clade, are the causative agents of vibriosis. This disease is currently responsible for mass mortality events and important economic losses in aquaculture farms. Improvement in surveillance and diagnostics are required to successfully manage vibriosis outbreaks. The 16S rRNA gene sequencing is often considered as the reference gold standard for bacterial identification but the cost and long processing time make it difficult to apply for routine identification. On the contrary, MALDI-TOF MS offers a rapid diagnosis and is today commonly used in veterinary laboratories. The major limiting factor is the low environmental bacterial diversity in the commonly available databases. Indeed, our work demonstrates that the single use of the commercially available Bruker BioTyper database is not fully adequate for identification of Vibrio bacteria isolated from aquaculture farms. Consequently, this study reports the development of a new in-house database named Luvibase. This latter is composed of 23 reference MALDI-TOF mass spectra profiles obtained from Vibrio collection strains, mostly belonging to the Harveyi clade. The accuracy of MALDI-TOF MS profiling and 16S rRNA gene sequencing was compared and revealed a lack of resolution power for 16S rRNA gene sequencing. In contrast, MALDI-TOF MS profiling has proved to be a more reliable tool for resolving species-level variations within the Harveyi clade. Finally, the implementation of the Bruker v.9.0.0.0 database with the Luvibase, allowed the successful identification of 47 Vibrio isolates obtained from moribund raised abalone, seabass and oysters. Thus, the use of the Luvibase allow for increased confidence in identifying species belonging to the Harveyi clade.