Streptococcosis is the most important bacterial disease in tilapia (Oreochromis sp.) production worldwide. It is caused mainly by Streptococcus agalactiae (GBS) serotypes Ia, Ib, III, IV, and IX in tilapia. Antibiotic resistance has been described for GBS in aquaculture, for this reason, it has an urgent need to discover new alternative therapies to control bacterial diseases. Phytoextracts have shown efficient activity against the most important bacterial pathogens in aquaculture. ALLIUM-OR® is a product composed of Allium sativum, Origanum vulgare, and ascorbic acid. TUR-AQUA® has Curcuma longa, Cinnamonium verum and choline chloride. We evaluated in vitro different doses of both products against S. agalactiae Ib. Streptococcus agalactiae (GBS) Ib was aerobically cultured for 24 h at 30 °C until the exponential growth phase was reached at 5,7 x 104 ufc/ml. Four doses of each product were incubated with GBS at 30ºC for 24 to 48h. All were tested in triplicate. ALLIUM-OR® completely inhibited the growth of S. agalactiae Ib in the different doses evaluated. TUR-AQUA did not show an inhibitory effect on Streptococcus agalactiae Ib growing at any concentration tested.
Oils and extracts of Allium sativum have been evaluated previously for their effect against S. mutants, S. pyogenes in humans, and S. iniae and S. agalactiae in vitro and in vivo in tilapia and trout with similar results to our study. Origanum vulgare had been evaluated against S. agalactiae Ib and our results showed that in combination with Allium sativum inhibited the growth of GBS Ib. Curcuma longa and Cinnamonium verum did not have an effect to reduce the growth of this bacterium. ALLIUM-OR® with Allium sativum, Origanum vulgare, and ascorbic acid inhibited the growing of GBS Ib and further studies are necessary to evaluate its effect in natural outbreaks.