Efficacy of Aeromonas hydrophila S-layer bacterins with different protein profiles as a vaccine in Nile tilapia (Oreochromis niloticus)

Farming of Nile tilapia is in full development throughout the world. However, an increase is still seen in the prevalence and severity of bacterial diseases. The aim of this study was to develop a vaccine against Aeromonas hydrophila in Nile tilapia (Oreochromis niloticus) based on protein patterns of S-layer proteins. The proteins were extracted using glycine and NaOH with subsequent visualization through SDS-PAGE. Based on the protein patterns observed, bacterins were produced that were tested in an experiment in vivo with the use of 144 fingerlings of Nile tilapia that were distributed in 24 aquariums in a completely randomized design. Eight distinct protein patterns were observed in SDS-PAGE, with apparent molecular mass from 52 to 72 kDa. All the unvaccinated fish inoculated with A. hydrophila died within 24 h after inoculation. The bacterins produced reduced the probability of death of the vaccinated fish when compared to unvaccinated ones. Hepatic histological analysis showed that the use of vaccines was able to revert changes in the liver of the fish. Key words: S-layer protein, SDS-PAGE, Aeromonas hydrophila, vaccine, Oreochromis niloticus.