The pathogenic bacterium Streptococcus agalactiae is one of the main obstacles in tilapia farming worldwide. This project aimed to evaluate the immunoglobulin-IgM of Nile tilapia fed with AQUA-PHOTO® probiotic (composed of Bacillus subtilis and Lactobacillus plantarum ) and vaccinated against Streptococcus agalactiae .
The experimental design was completely randomized, with five treatments (CON – control; ADJ - only adjuvant injected, without probiotic feeding; PRO - with probiotic and without the vaccine; VAC - without probiotic and with the vaccine; PRO+VAC - with probiotic and with the vaccine) and five replicates , for 63 days . The fish was fed with ration + probiotic for 21 days (PRO and PRO+VAC). The fish was vaccinated at 21th day and revaccinated (booster) at 35th day of experiment. The fish blood (n=10 per treatment) was collected after anesthesia with eugenol (0.02 mg.L-1 ) at day 21 (phase I), 35 (phase II) , 49 (phase III) and 63 (phase IV) of experiment. The IgM antibodies d etection was performed in tilapia serum by indirect ELISA with S. agalactiae bacterin , Nile tilapia anti-IgM polyclonal antibody produced in rabbit , anti-rabbit IgG, peroxidase-conjugated and, the colorimetric substrate tetramethylbenzidine (TMB) . The reaction was read at spectrophotometer (450 nm).
In p hase III, the fish IgM quantification of PRO+ VAC was higher than other treatments (P<0.001) and VAC values was higher than CON, ADJ and PRO , but only lower concentration than PRO+VAC (P<0,05).
We conclude that PRO+VAC and VAC at phase III, provide good production of IgM of Nile tilapia after infection with S. agalactiaea and probable will protect against S. agalactiae infection.