Protective efficacy of phage PVN02 against haemorrhagic septicaemia in striped catfish Pangasianodon hypophthalmus via oral administration

Abstract

Haemorrhagic septicaemia caused by Aeromonas hydrophila in striped catfish (Pangasianodon hypophthalmus) is one of the most important aquatic diseases in the Mekong Delta, Vietnam. However, antibiotic‐resistant A. hydrophila strains have become popular and resulted in inadequate control of the disease in striped catfish farms. This study investigates the protective efficacy of bacteriophage PVN02 against haemorrhagic septicaemia in striped catfish via oral administration. The phage‐containing pellets were prepared by spraying the phage solution on food pellets at 20 ml/kg. The rate of phage desorption from the food pellets into the water was very low; the phage titres in the water were approximately log 1.0 PFU/ml or undetectable. The in vivo experiment evaluating the protective efficacy of PVN02 against haemorrhagic septicaemia in striped catfish was conducted using 21 groups of 1,260 fish in 50‐L plastic tanks in triplicate. The catfish were fed twice daily with phage‐sprayed pellets. Different densities of bacterial suspensions were added into the tanks for 24 hr. Without the existence of the phage, the highest mortality rate was 68.3 ± 2.9% at the highest density of bacterial suspension. In contrast, the mortality rate at the highest density of bacterial suspension was significantly reduced to 8.33 ± 2.9% or 16.67 ± 2.9% at the phage dose of log 6.2 ± 0.09 or log 4.2 ± 0.09 PFU/g. This study provides a very practical manner of applying phage therapy to prevent disease in large‐scale striped catfish farms.

Characterization and protective effects of lytic bacteriophage pAh6.2TG against a pathogenic multidrug-resistant Aeromonas hydrophila in Nile tilapia ( Oreochromis niloticus )

“…Cao et al (2020) applied phage MJG by injection, immersion, and oral administration to control a pathogenic A. hydrophila in rainbow trout and the fish gained RPS of 100%, 66.7%, and 50%, respectively. Dang et al (2021) showed protective efficacy of phage PVN02-sprayed feed against A. hydrophila 4.4T in striped catfish with RPS from 75.6 -87.8%.…”

“…In addition, intraperitoneal injection of phages FpV4 and FPSV-D22 showed protection of rainbow trout (Oncorhynchus mykiss ) to Flavobacterium psychrophilum with RPS of 53.8%, while feed-based and bath administrations were not effective (Donati et al, 2021). Previous studies have demonstrated that phages can be applied in aquaculture to combat A. hydrophila infection (Anand et al, 2016;Cao et al, 2020;Dang et al, 2021;Jun et al, 2013;Le et al, 2018). Hence, strategy using phages for biocontrol of A. hydrophila has become increasingly attractive.…”

Phage Revolution Against Multidrug-Resistant Clinical Pathogens in Southeast Asia

“…There is also a notable amount of research on in vitro testing of phages, including the testing for the phage's host range, biocontrol assays against pathogens, and phage formulation techniques. We retrieved a few publications on in vivo testing of phages using invertebrates, such as moth (Wintachai et al, 2019; and oysters (Le et al, 2020); in vivo vertebrate model systems included zebrafish (Assafiri et al, 2021), catfish (Le et al, 2018;Dang et al, 2021), tilapia (Dela Cruz-Papa et al, 2014, chicken (Wong et al, 2014;Kaikabo et al, 2017), and mice (Guang- Han et al, 2016). Lastly, a few publications focused on the applications of phages in combating MDR organisms.…”

“…Another study of lung infections caused by B. pseudomallei in mice indicated that phages administered peritoneally successfully protected the animals from disease progression and mortality (Guang- Han et al, 2016). Other in vivo phage therapy studies focused on treating infections in poultry (Wong et al, 2014;Kaikabo et al, 2017) and aquaculture (Dela Cruz-Papa et al, 2014Le et al, 2018;Dang et al, 2021). The implications for clinical use, however, may not be apparent especially if the bacterial pathogen is specific only to the animal (i.e., A. hydrophila in freshwater fishes, avian pathogenic E. coli in birds, and Vibrio alginolyticus in oysters).…”

Genomic analysis of \(\textit{Aeromonas hydrophila}\) bacteriophages isolated in striped catfish farms in the Mekong delta, Vietnam

“…The efficacy of phage therapy for the prevention and treatment of bacterial diseases in fish and shellfish has been reviewed (Doss et al, 2017;Culot et al, 2019). Some studies about phages to control A. hydrophila and other bacterial pathogens in striped catfish have been published since 2018 (Le et al, 2018;Hoang et al, 2018;Hoang et al, 2019;Dang et al, 2021).…”