Isolation and characterization of the lytic bacteriophages and their application in combination with amoxicillin against Aeromonas dhakensis

Aeromonas dhakensis stands out as the most potent Aeromonas species causing a range of human diseases. This research marks the pioneering effort in isolating and characterizing virulent phages targeting A. dhakensis. Only the AM isolate among the Aeromonas isolates showed compatibility for phage isolation and was identified as A. dhakensis. Computational analysis identified the presence of virulence factors and antimicrobial resistance genes in A. dhakensis AM. Phage isolation was conducted using this particular strain as the host, resulting in the isolation of four virulent phages: vB_AdhM_DL, vB_AdhS_TS3, vB_AdhM_TS9, and vB_AdhS_M4. Bacterial numbers significantly decrease after both pre-treatment and post -treatment with individual phages and phage cocktails, ranging from 2.82 to 6.67 log CFU/mL and 4.01 to 6.49 log CFU/mL, respectively. Combining a phage cocktail with sub-MIC amoxicillin led to complete inactivation in both pre-treatment and post -treatment scenarios within a 200 mu L volume. The complete genomes of phages vB_AdhM_DL, vB_AdhS_TS3, and vB_AdhM_TS9 were determined to be 42,388 bp, 115,560 bp, and 115,503 bp, respectively. This study establishes the effectiveness of using phages as an complement with sublethal antibiotic concentrations, presenting a potential and effective therapeutic approach.