PENAMBAHAN KANDIDAT PROBIOTIK Bacillus methylothrophicus SECARA BERKALA PADA MEDIA PEMELIHARAAN UNTUK PENCEGAHAN INFEKSI BAKTERI Aeromonas hydrophila PADA IKAN NILA (Oreochromis niloticus)

Abstract

Aeromonas hydrophila is a bacteria that causes of MAS disease (motile aeromonad septicemia) in freshwater fish cultivation and can cause mass death in a fairly short period of time in some species including tilapia. There are several alternative strategies in prevention, one of which is the use of probiotic bacteria as agents for controlling or preventing this disease. One candidate for probiotics that has been molecularly identified as 16sRNA and is known to have the ability to inhibit pathogenic bacteria is B. methylotrhrophicus. The aim of this research was to study B.methylotrophicus in inhibiting  A. hydrophila in Oreochromis niloticus culture. This research consisted of in vitro and in vivo test that used experiment method with completely randomized design with 4 treatments (density of 1 fishes/l) and 3 replications. The treatment consisted of a mixture of A. hydrophila 102 CFU/mL with B. methylotrophicus 109 CFU/mL (a) without addition of B. methylotrophicus (b) Addition every 3 days, (c) Addition every 5 days, (d) Addition every 7 day. 120 fishes at average weight of 17,5±1,9 g was used as experimental animals. Based on the in vitro test, the most powerful concentration of B. methylotrophicus to inhibit A. hydrophila was 109 cfu/mL with clear zone of 24,9±4,2 mm. In vivo tests show that the addition of B. methylotrophicus periodecally does not significantly affect survival rates, but can slow the gowth of A. hydrophila. Treatment D showed the highest survival rate (13.33%), followed by treatment A (6.66%), B (3.33%), and C (3.33%). These results indicate that B.methylotrophicus can prevent the gowth of A. hydrophila in vitro, and can increase SR by 6.66% in the in vivo test.