Aquaculture America 2024

February 18 - 21, 2024

San Antonio, Texas

ISOLATION AND CHARACTERIZATION OF PHAGE AHFM11 AGAINST HYPERVIRULENT Aeromonas hydrophila AND ITS USE IN AQUACULTURE AS A THERAPEUTANT

Nithin Muliya Sankappa1,2,3, Kushala Kallihosure Boregowda1, Girisha Shivani Kallappa1, Linnea K. Andersen3 , Suresh Thangavel1 , Jason W. Abernathy3

1 Department of Aquatic Animal Health Management, College of Fisheries, Karnataka Veterinary, Animal and Fisheries Sciences University, Matsyanagar, Mangalore-575002, Karnataka, India

2Oak Ridge Institute for Science and Education (ORISE), ARS Research Participation Program, Oak Ridge, TN, 37830, USA

3USDA-ARS Aquatic Animal Health Research Unit (AAHRU), 990 Wire Road, Auburn, AL 36832, USA

nithin.sankappa@usda.gov

 



 Phages infecting hypervirulent  Aeromonas hydrophila  (vAh) had  not  been isolated anywhere in the world ; however,  phages have been isolated against  motile Aeromonas septicemia (MAS) with only few of them having been characterized. This study aimed at developing therapeutic phage against hypervirulent Aeromonas hydrophila infection in aquaculture systems.

 A total of 110  water  samples were collected aseptically. A novel phage AhFM11 specific to hypervirulent A. hydrophila  was isolated and shows  lytic  activity against reference A. hydrophila (ATCC 35654). Soft agar overlay method was used to determine titer and found to be 1.58 x 10 10 pfu/mL . Host range of the AhFM11 phage was performed for 131 Aeromonas spp. and 10 non Aeromonas. The results indicated that AhFM11 had a broad host range, infecting 65 Aeromonas species. Also, it was found that this phage did not harbor any antibiotic resistance genes. This is the first report of phage against  hypervirulent A. hydrophila.

Transmission electron microscopy (TEM) revealed that phage AhFM11 belongs to the family of Myoviridae (Figure 1). O ne-step growth curve of AhFM11 shown that the phage has an average burst size of 276 ± 15 PFU per infected cell, adsorption rate of 97.3% and found to be stable in different environmental conditions. The AhFM11 genome comprised of 176,963 bp with an average G/ C content of 41.5% (NCBI accession No. MZ450807.1). The novel bacteriophage-based strategies therapeutic approach (injection, oral feed and immersion) to prevent and treat A. hydrophila infection were studied. Therapeutic application in injection, immersion and feed impregnated phages showed 100%, 95.11% and 93.11% survival than the challenged untreated fishes.  These findings support that phage AhFM11 can be used to treat/control A. hydrophila  infection in cultured fishes and  has  immense value as a potential alternative to antibiotics.