Study of Probiotic Candidate Bacteria CBL20 for Inhibiting of Aeromonas hydrophila with Different Concentration in Tilapia (Oreochromis niloticus)

Abstract

Aero moniasis is still a problem in tilapias culture industry since its caused mass mortality. Manipulation microbial population in the culture media using probiotic to prevent pathogenic bacterial bloom is becoming the most environmentally friendly approach. Probiotic candidate CBL20 was mo lecularly identified through 16s RNA method as Bacillus methylotropicus. The purposes of this study were to determine the ability of CBL20 to inhibit the growth of pathogenic bacteria (Aeromonas hydrophila) in vitro and to evaluate the performance of CBL20 to prevent Aeromoniasis outbreaks in vivo. Survival rate of experimental animals was observed. The 120 fish (Oreochromis niloticus) at an average weight of 11.85 + 1.02 g were used as experimental animals. Completely randomized design with 4 treatments and 3 replications was applied. The treatments were various mixture concentration of probiotic CBL20 at 106 CFU ml-1 with bacterial A. hydrophila (a) 0 CFU ml-1, (b) 102 CFU ml-1, (c) 103 CFU ml-1, and (d) 104 CFU ml-1. In vitro showed that CBL20 at a concentration of 106 CFU ml-1 were inhibited A. hydrophila with growth inhibition area of 9.3 + 0.9 mm. Addition of CBL20 as a candidate probiotic bacteria with concentration 106 CFU ml-1 has not been able to inhibit A. hydrophilla in the treatment given. The concentration of treatment did not have a significant effect (P> 0.05) on the survival of tilapia. CBL20 probiotic candidates with a concentration of 106 CFU ml-1 were able to maintain SR 33.33% for 14 days after infected by A. hydrophilla.