DEVELOPMENT OF THERAPEUTIC PHAGE CONSORTIA TO MANAGE AEROMONAS HYDROPHILA INFECTION IN AQUACULTURE SYSTEMS
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Date
2021
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KARNATAKA VETERINARY, ANIMAL & FISHERIES SCIENCES UNIVERSITY, BIDAR
Abstract
Motile Aeromonas Septicemia has contributed to severe economic loss in several aquaculture fish species such as carps, tilapia, salmons, and catfishes. In the present study, water and diseased fish samples were collected. Diseased fishes had a clinical sign such as enlarged abdomen, reddening, dropsy, fin rot and haemorrhages on the body surface. The etiological agent was identified as Aeromonas hydrophila and other Aeromonas spp. through biochemical and molecular methods. Further, Multiple Antibiotic Resistance (MAR) index showed >0.2 for the isolated A. hydrophila (n=35), which indicates the property of multidrug resistance. Therefore, as a preliminary approach to develop bio-control measure, novel lytic bacteriophages (phages AhFM1-AhFM22) were isolated from different water systems. Transmission electron microscopy (TEM) confirms that the lytic phages AhFM1 to AhFM11 & AhFM12 belong to family of Myoviridae and Siphoviridae respectively. Interestingly, phages (AhFM1- AhFM11) displayed adsorption in the range of 70 to 96%; latent period 15 to 25 min and burst 65 ± 27 PFU/host cell to 348 ± 13 PFU/host cell. The phages were stable over broad array of physicochemical parameters (temperatures, salinity, pH and chloroform). The novel bacteriophage-based strategies viz., prophylactic and therapeutic approach (injection, oral and immersion) to prevent and treat A. hydrophila infection were studied for first time in India. Prophylactic application in injection, immersion and feed impregnated phages showed 100%, 95.11% and 93.11% survival than the challenged untreated fishes. Therapeutic approach (injection) has resulted in 100% survival in initial (0 and 24) hours of treatment and delay in therapy resulted in 80% and 75% survival at 48 and 72 hr respectively. These findings support that phages (AhFM1-AhFM11) can be used to treat/control A. hydrophila infection in cultured fishes and have an immense capability to develop as a substitute to antibiotics