SUPERTROUT is a European project aimed at improving sustainability and performance of aquaculture farming system mainly through the breeding for lactococcosis resistance in rainbow trout and the development of an orally administered recombinant protein vaccine.
Among infectious diseases, lactococcosis, sustained by Lactococcus garvieae , a warm water pathogen, is a major re-emerging bacterial disease, seriously affecting the sustainability of aquaculture industry worldwide. Lactococcosis is a septicaemic disease characterized by high mortality and great economic loss. The severity of the symptoms could vary according to the pathogenicity of the bacterial strain, fish species and size, and abiotic parameters such as water temperature and for this reason it is enhanced by global warming.
In the context of SUPERTROUT, genomes comparison and the characterization of L. garvieae strains, collected along the time in natural outbreaks recorded in Italy, Greece, Spain, and Turkey allowed to re-allocate different strains, previously classified L. garvieae , as Lactococcus petauri , a recently described novel species of the genus Lactococcus . L. petauri has been previously reported in California and Brazil and from our data, it appears widely spread in the Mediterranean area, with the only exception of Italy in which all the analyzed strains were L. garvieae . L. garvieae was routinary diagnosed using biochemical test, specific PCR targeting 16S and MALDI-TOF, but due to the high genetic similarity level, these methods failed to discriminate between the two species. Results obtained led us to develop new molecular and discriminating diagnostic tool such as a PCR based on ITS 16S-23S rRNA and to study differences in terms of pathogenesis (based on capsule genes cluster and hemolysins genes) and antimicrobial resistance.
Strains characterization associated to reverse vaccinology is particularly important to develop vaccines specifically targeting L. petauri , considering that actually only L. garvieae vaccines are available and to apply the appropriate antimicrobial treatment in field.