Phage pAh6.2TG improved survivability of Nile tilapia challenged with the MDR A. hydrophila
In vivo experiment showed that 100% fish in negative control group (no Ah + no phage) survived after 14 days, while only 25% survival was recorded in positive control group (Ah + no phage) (Figure 5). Interestingly, there was 62.5% and 80% survival in groups treated with pAh6.2TG with MOI = 0.1 (Ah + phage 0.1) and MOI = 1.0 (Ah + phage 1.0), respectively. These differences in percentage of survival of 2 phage treated groups were not statistically significant (p = 0.154) but statistically significant with positive control group (p = 0.000). The remaining two groups treated with phage without bacteria had 95 – 100% survival. The relative percent survival (RPS) of two treatments groups were 50% (MOI = 0.1) and 73.3% (MOI = 1), respectively. The moribund fish in challenge groups showed behavioral abnormalities (lethargy, loss of appetite, and surface swimming) and pale liver. Using selective medium, pure colonies with morphological characteristics of A. hydrophila were successfully isolated from representative dead fish (n=3).