Isolation, antibiotic resistance examination, and genomic characterization of pathogenic bacteria from Channa argus

Abstract:

[Background] Snakehead fish (Channa argus) is an important species of freshwater economic fish. The farming industry of C. argus is developing rapidly, while diseases, especially bacterial diseases, have become a bottleneck restricting the sustainable development of this industry. [Objective] To gain deep insights into the antibiotic resistance and infection mechanisms of the pathogens from C. argus and provide scientific guidance for disease prevention and control. [Methods] Three pathogen strains (SY1, SY3, and SY7) were isolated from diseased C. argus and subjected to antibiotic susceptibility testing and whole genome sequencing. The virulence genes, resistance genes, prophages, as well as potential virulence and resistance genes carried by the prophages, were annotated based on the whole genome sequencing data. [Results] Based on 16S rRNA sequencing and genomic average nucleotide identity (ANI) analysis, strains SY1, SY3, and SY7 were identified as Shewanella xiamenensis, Aeromonas dhakensis, and Nocardia seriolae, respectively. Antibiotic susceptibility testing revealed that these pathogens had resistance to multiple antibiotics, and all showed resistance to penicillin, oxacillin, ampicillin, erythromycin, clarithromycin, azithromycin, vancomycin, and lincomycin. The genome sizes of strains SY1, SY3, and SY7 were 4 895 555 bp (G+C content of 46.23%), 4 853 433 bp (G+C content of 61.54%), and 9 294 386 bp (G+C content of 68.24%), respectively. A total of 171 virulence genes were detected in the genomes of the three pathogens, and they were involved in motility, adherence, exotoxin, effector delivery system, nutrition/metabolism, and stress responses. The genes conferring resistance to 15 categories of antibiotic were detected in the bacteria. Prophage prediction analysis revealed that all the three strains carried prophages, while no virulence or antibiotic resistance genes were detected in the prophage sequences. [Conclusion] This study expands our understanding of antibiotic resistance and infection mechanisms of pathogens from C. argus, providing a scientific basis for the prevention and treatment of diseases in Channa argus.

Key words:Channa argus;pathogenic bacteria;antibiotic susceptibility;virulence gene;antibiotic resistance gene;prophage