Characterization and potential application of Thurincin H as an alternative to antibiotics in the control of...

In aquaculture, controlling emerging pathogenic bacteria is crucial, making the search for new antimicrobials a priority. We evaluated the antibacterial activity against Streptococcus iniae under in vitro and in vivo conditions of the bacteriocin Thurincin H (ThurH), recombinantly produced in Bacillus thuringiensis genotype Cry-B-pThur and purified via molecular weight screening. The results show that ThurH is stable in seawater and inhibits the growth of S. iniae by 100% at 70 µg/ml, with a MIC of 35 µg/ml. Bactericidal activity was observed within the first 10 min (16 MIC), eliminating 100% of viable cells. The in vivo assay with Artemia franciscana demonstrated that ThurH is non-toxic at 1000 µg/ml. Challenge tests with A. franciscana at 100 mL (4 artemias/mL) and histological analysis demonstrated the efficacy of ThurH in in vivo trials, improving organism survival with two doses (MIC). These results demonstrate for the first time in an in vivo assay that ThurH has potential as an antimicrobial against S. iniae in aquaculture.