Isolation and characterization of Aeromonas hydrophila-specific lytic bacteriophages

Aeromonas hydrophila can infect a broad range of fish living in freshwater and estuaries. Because the majority of A. hydrophila is resistant to antimicrobials, alternative treatment strategies should be developed. Bacteriophage may be an alternate approach to control infectious diseases. For this reason, we isolated AP-T65, AP-T5, AP-Y28, and AP-AT phages and assessed their lytic activity against A. hydrophila strains, described them phenotypically, kinetically, and genetically, and evaluated their cytotoxicity in vitro and in vivo assays. After sequencing the major capsid protein (MCP) gene of the phages, it was found that all phages belonged to the Myroviridae family. Phages demonstrated lytic activity against Aeromonas sp., A. salmonicida, A. veronii, and A. media. Phages had a short latent period of roughly 10-15 min and the burst sizes of all Aeromonas phages were found to be between 10 and 20 plaque forming units (PFU)/infected cell. The AP-T65, AP-T5, AP-Y28, and AP-AT phages survived a wide range of pH values ranging from 3 to 10, as well as temperatures ranging from 4 to 37 degrees C. Aeromonas phages showed no impact on fish or EPC cell lines. Therefore, Aeromonas phages are safe and they can be used as a cocktail to treat A. hydrophila infection. Because of their short latent period and greater burst size, phages isolated in the present study would be ideal candidates for phage therapy, and they might be used as a cocktail for improved control effects. The application of a cocktail of these phages may also prevent the formation of phage-resistant bacteria.

Automated summary

In this study, several lytic phages against A. hydrophila were isolated and characterized. These phages demonstrated cytotoxicity against A. hydrophila strains in vitro and in vivo, but showed no impact on fish or cell lines. Therefore, these phages can be used safely as a cocktail for treating A. hydrophila infection.