Isolation, Characterization, and Application of a Bacteriophage Infecting the Fish Pathogen Aeromonas hydrophila.

Muhammad Akmal,Ali Hussain,Tae-Jin Choi,Aryan Rahimi-Midani,Muhammad Hafeez-Ur-Rehman

doi:10.3390/pathogens9030215

Muhammad Akmal, Ali Hussain + Show 3 more

Open Access

https://doi.org/10.3390/pathogens9030215

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Abstract

Bacteriophages are increasingly being used as biological control agents against pathogenic bacteria. In the present study, we isolate and characterize bacteriophage Akh-2 from Geoje Island, South Korea, to evaluate its utility in controlling motile Aeromonas septicemia. Akh-2 lysed four of the seven Aeromonas hydrophila strains tested. Transmission electron microscopy analysis showed that Akh-2 belongs to the Siphoviridae family, with head and tail sizes of 50 ± 5 and 170 ± 5 nm, respectively. One-step growth curve analysis revealed that the phage has a latent period of 50 ± 5 min and a burst size of 139 ± 5 plaque-forming units per infected cell. The phage appeared stable in a pH range of 6–8 and a temperature range of −80 to 46 °C. Based on next-generation sequencing analysis, its genome is 114,901 bp in size, with a 44.22% G + C content and 254 open reading frames. During an artificial induction of the disease, loach (Misgurnus anguillicaudatus) treated with Akh-2 showed an increased survival rate and time compared with the non-treated control. Our results suggest that Akh-2 is a potential biological agent for the treatment of Aeromonas infections in fish.

Highlights

Aquaculture is the fastest-growing food-production sector worldwide
Bacterial fish diseases are usually treated with antibiotics, and it is the reason for leakage to the environment and selection of resistance
Considering the advantages of biological disease control in aquaculture and the prevalence of the host bacterium in seawater, the present study aims to isolate and characterize a potentially suitable bacteriophage against A. hydrophila from water samples collected from marine environments

Summary

Introduction

Aquaculture is the fastest-growing food-production sector worldwide. In 2014, aquaculture produced nearly 74 million tons of fish, approximately 45% of the global production of fish-based food [1]. A Gram-negative rod-shaped bacterium, is the main cause of the disease motile Aeromonas septicemia, known as tail and fin rot. This bacterium causes serious infections in various freshwater fish species, including loach (Misgurnus anguillicaudatus), channel catfish (Ictalurus punctatus), and common carp (Cyprinus carpio), and infects some marine fish species to a lesser extent [4].

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