IJSRP, Volume 5, Issue 7, July 2015 Edition [ISSN 2250-3153]
Ngoc Tuan Tran, Ze-Xia Gao, James Milton, Li Lin, Yang Zhou, Wei-Min Wang
This study was carried out to confirm whether Aeromonas hydrophila is a main haemorrhagic pathogen in blunt snout bream Megalobrama amblycephala (BSB). The fish was challenged with bacterial concentrations of 1.7×104, 1.7×105, 1.7×106 and 1.7×107 cfu/fish for 7 days post infection. The results showed that mortality was bacterial-dose dependent, with 100% mortality observed at 1 day at the highest dose level (1.7×107 cfu/fish). For comparison, control fish exhibited cumulative mortalities of 0%. The median lethal dose (LD50) was 5×105 cfu/fish. A total of 15 bacterial strains of Aeromonas were re-isolated from challenged fish and re-identified based on morphological characteristics, biochemical tests and genomic DNA gene sequencing. No bacteria were isolated from the control group. This study results indicated that A. hydrophila is capable of causing haemorrhagic septicaemia in BSB. Antibiotic susceptibility test with two strains D4 and HU201301 was investigated; both strains showed sensitive to most of the tested drugs.