Emerging novel bacteriophage candidates targeting multidrug-resistant Aeromonas spp. from striped catfish Pangasianodon hypophthalmus

The escalating threat of antibiotic resistance in aquatic pathogens has intensified interests in bacteriophage-based solutions for the sustainable aquaculture development. This study characterized two lytic phages, vB_AerC_LA93P1 and vB_AerC_LA93P2, isolated from striped catfish pond water samples. They demonstrated potent activity against Aeromonas dhakensis , an emerging agent posing a significant threat in striped catfish farming in Vietnam. Both phages exhibited considerable lytic capabilities across multidrug-resistant Aeromonas spp. isolates, when lysing 14 out of 16 tested Aeromonas spp. isolates, respectively. One-step growth curve experiments revealed that LA93P1 has a latent period of 30 mins and a burst size of approximately 506 ± 97 PFU per infected cell, while LA93P2 has a latent period of 35 mins and a larger burst size of 591 ± 89 PFU per infected cell. Genomic analysis revealed double-stranded DNA genomes of 52,193 bp (LA93P1) and 52,064 bp (LA93P2) with GC contents of 52.8 % and 52.9 %, respectively. Functional annotation identified 68 and 70 open reading frames (ORFs), including structural, replication, and lytic modules, with no of antibiotic resistance genes, virulence factors, or lysogeny-associated elements. Comparative genomics and phylogenetics placed both phages LA93P1 and LA93P2 within the family Chaseviridae and they shared the highest nucleotide identity (76 % and 81 %, respectively) with Aeromonas phage ZPAH14 (NC 070840). The absence of unsafe risks and their obligately lytic nature position both phages as promising candidates against multidrug-resistant Aeromonas spp. in striped catfish. • The phages represented a novel species within an established genus • The phages were effective in repression of the multidrug-resistant Aeromonas spp. • It was the first report of phages infecting A. dhakensis isolates from striped catfish farms.