Bacteriophage therapy using novel Aeromonas phage PAS-1 can be an alternative method to control salmonid furunculosis caused by antibiotic-resistant Aeromonas salmonicida subsp. salmonicida

Abstract

Aeromonas (A.) salmonicida subsp. salmonicida is the causative agent of furunculosis and bacterial septicemia in a broad variety of fish including salmonids, and is thus responsible for significant economic losses in the global aquaculture industry. Recently, the acquisitions of antibiotic resistance in the bacteria have been recognized as serious concerns. To search for the alternative biocontrol agents against this fish pathogen, the morphological, molecular and several biological characteristics of the lytic Aeromonas bacteriophage (phage) PAS-1 were investigated, and its therapeutic potential against A. salmonicida subsp. salmonicida infections were simultaneously evaluated. The phage showed broad host ranges to other subspecies of A. salmonicida as well as A. salmonicida subsp. salmonicida including antibiotic-resistant strains. The PAS-1 was morphologically classified as Myoviridae and possessed approximately 48 kb of ds DNA genome. And according to the genomic and proteomic analysis, the phage was closely related to other Myoviridae phages infecting enterobacteria or Aeromonas species. For the therapeutic applications of PAS-1, the phage was preferentially co-cultured with one virulent A. salmonicida subsp. salmonicida strain that possesses the type III secretion system (TTSS) related ascV gene, and strong bacteriolytic activity was observed against the bacteria. Administration of the phage in rainbow trout (Oindustry. Recently, the acquisitions of antibiotic resistance in the bacteria have been recognized as serious concerns. To search for the alternative biocontrol agents against this fish pathogen, the morphological, molecular and several biological characteristics of the lytic Aeromonas bacteriophage (phage) PAS-1 were investigated, and its therapeutic potential against A. salmonicida subsp. salmonicida infections were simultaneously evaluated. The phage showed broad host ranges to other subspecies of A. salmonicida as well as A. salmonicida subsp. salmonicida including antibiotic-resistant strains. The PAS-1 was morphologically classified as Myoviridae and possessed approximately 48 kb of ds DNA genome. And according to the genomic and proteomic analysis, the phage was closely related to other Myoviridae phages infecting enterobacteria or Aeromonas species. For the therapeutic applications of PAS-1, the phage was preferentially co-cultured with one virulent A. salmonicida subsp. salmonicida strain that possesses the type III secretion system (TTSS) related ascV gene, and strong bacteriolytic activity was observed against the bacteria. Administration of the phage in rainbow trout (O