Oral feed-based administration of phage cocktail protects rohu fish (Labeo rohita) against Aeromonas hydrophila infection

• Published in: Archives of microbiology Vol. 206; no. 5; p. 219
• Main Authors: Rai, Sumeet, Tyagi, Anuj, B. T., Naveen Kumar
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.05.2024; Springer Nature B.V
• Subjects: Aeromonas hydrophila; Animals; Bacteriophages; Biochemistry; Biomedical and Life Sciences; Biotechnology; Cell Biology; Cyprinidae; Ecology; Fish; Fish Diseases - prevention & control; Freshwater fish; Gram-Negative Bacterial Infections - prevention & control; Gram-Negative Bacterial Infections - veterinary; Labeo rohita; Life Sciences; Medicated feeds; Microbial Ecology; Microbiology; Mortality; Oral administration; Original Paper; Phages; Room temperature; Spraying; Survival; Bacterial pathogens; Phage therapy; Oral administration; Fish culture; Aeromonas hydrophila
• ISSN: 0302-8933; 1432-072X
• DOI: 10.1007/s00203-024-03951-3

Aeromonas hydrophila is one of the major freshwater fish pathogens. In the current study, a cocktail of D6 and CF7 phages was given orally to Labeo rohita to assess phage survival in fish organs as well as to determine the therapeutic efficacy of phage treatment against fish mortality caused by A. hydrophila . In the phage-coated feed, prepared by simple spraying method, phage counts were quite stable for up to 2 months with a decline of ≤ 0.23 log 10 and ≤ 1.66 log 10 PFU/g feed during 4 o C and room temperature storage. Throughout the experimental period of 7 days, both phages could be detected in the gut of fish fed with phage-coated feed. Besides, both CF7 and D6 phages were also detected in fish kidneys indicating the ability of both the phage to cross the intestinal barrier. During challenge studies with LD 50 dose of A. hydrophila , phage cocktail doses of 1 × 10 6 – 1 × 10 8 PFU/g feed prevented the mortality in L. rohita with relative percentage survival (RPS) of 8.7–65.2. When challenged with LD 90 dose of A. hydrophila , an RPS value of 28.6 was obtained at a phage cocktail dose of 1 × 10 8 PFU/g feed. The RPS data showed that orally-fed phage cocktail protected the fish against the mortality caused by A. hydrophila in a dose-dependent manner. Simple practical approaches for phage cocktail development, medicated feed preparation and oral administration along with phage survival and protection data make the current study useful for farmer-level application.