Phage pAh6.2TG suppressed bacterial concentration in water and fish tissue
Fluctuation of bacterial concentration and phage titer in water and fish liver are shown in Figure 6 and Table S3. In rearing water, after 3 h of bacteria and phages exposure, bacterial concentration reduced 6.7 ± 0.5 folds in group treated with phage MOI = 0.1, and 18.1 ± 6.98 folds in group treated with phage MOI = 1.0 (Figure 6A). The calculation of fold changes is displayed in Table S3. In contrast, after 3 h, bacterial concentration increased 10.2 ± 3.15 folds in Ah + no phage group. Simultaneously, phage titer in groups treated with phage MOI = 0.1 and 1.0 after 3 h increased 51.04 ± 5.16 folds, and 20.98 ± 1.03 folds, respectively (Figure 6B). Phage was absent in Ah + no phage control group. At 24 h post-challenge, bacterial concentration in three groups was increased, while phage concentration in water slightly decreased. Besides, slight reduction of bacterial and phage concentration was observed in all groups at 48 h post-treatment (Figure 6A – B).
Moreover, in fish liver, bacterial concentrations of 5.8 ± 0.14, 5.52 ± 0.06, 5.51 ± 0.24 logCFU/g were recorded in Ah + no phage, Ah + phage 0.1, and Ah + phage 1.0 groups, respectively (Figure 6C). In Ah + phage 0.1 and Ah + phage1.0 groups, phage titers were 4.55 ± 0.2 and 4.75 ± 0.12 logPFU/g, respectively (Figure 6D). Similar pattern of phage concentration in rearing water was observed at 48 h post-challenge, while bacterial load decreased in all groups. In fish liver, compared to 24 h post-treatment, bacterial concentration in Ah + no phage groups increased 10.69 ± 3.85 folds, while in Ah + phage 0.1 and Ah + phage 1.0 groups, bacteria decreased 2.7 ± 0.24 and 34.08 ± 26.4 folds, respectively (Table S3).
The bacterial load in fish liver of Ah + no phage group decreased 3.8 ± 0.64 folds, from 6.58 x 106 ± 3.18 x 105 at 24 h post-challenge to 1.75 x 106 ± 2.12 x 105 CFU/g at 72 h post-challenge (Table S3). The same pattern was recorded in Ah+ phage 0.1 and Ah + phage 1.0 groups with 4.03 ± 0.83 and 2.18 ± 0.96 fold-reduction, respectively (Table S3). At 72 h post-challenge, phage titer in fish liver decreased 15.13 ± 3.35 and 13.96 ± 3.95 folds in groups treated with phage 0.1 and 1.0 at 24 h post-challenge, respectively (Table S3).