Isolation and Characterization of Aeromonas hydrophila lytic Bacteriophages as a safe antibiotic alternative bio-control agent

Abstract

This study aimed to develop a safe bio-control approach for therapy and decontamination of Aeromonas hydrophila. The study focused on determination of the drug susceptibility of Aeromonas isolates from diseased tilapia; and establishment of a stock of partially characterized Aeromonas hydrophila bacteriophages. Eighteen (18) Aeromonas spp isolates were tested for antimicrobial resistance against 10 antibiotics. The susceptibility of the isolates to various antibiotics ranged from 0 to 100%. For bacteriophages, three lytic phages that had the highest host range (78.6% to 92.8%, n=28) were selected. Further characterization revealed a burst period of 20 ± 5 to 40 ± 5 minutes, a latent period that varied from 10 ± 5 to 40 ± 5 minutes; and burst size of 98–171 virions per infected cell. There were no significant changes in phage titers on exposure at 40°C and 50°C for 60 minutes (P = 0.05). However, a gradual decrease in the titres was observed at 60°C while a fast decline was noted at 70°C-90°C. All phages demonstrated at least some activity in the pH range of 1- 13. In water stability testing, the phages survived up to 22 days of the experiment, with a sharp decrease of 1 log PFU/mL to have been encountered within the first day. The findings of this study suggest phages as bio-control agents against Aeromonas infection in fish. However, further genomic characterization is required.