Isolation and characterization of phage (ETP-1) specific to multidrug resistant pathogenic Edwardsiella tarda and its in vivo biocontrol efficacy in zebrafish (Danio rerio)

Development of phage delivery by bioencapsulation of artemia nauplii with Edwardsiella tarda phage (ETP-1)

“…As suggested by other researchers, observed reduction in ETP-1 persistency or phage decay among tissues could be due to assemblage of factors such as the use of filtrating systems by higher organisms for removal of phages, production of phage neutralization antibodies, and irreversible adsorption to fish tissues [8,13]. We reported previously, that ETP-1 could withstand (40% survival) at the pH 3 up to 1 h in vitro, and completely loss the infectivity at ≤ pH 2 and ≥ 11 [23]. Thus, it could expect the stability issues of the phages while transporting through high acidic and proteolytic activity environments during oral delivery.…”

“…Bacteria strain and the bacteriophage E. tarda strain and its infecting phage ETP-1 were previously isolated from seawater obtained from marine aquaculture farm and characterized in detail [23]. The bacteria strain stored at − 80°C was streaked on a tryptic soy agar (TSA) plate and incubated over night at 25°C.…”

“…Filtrate was identified as F1, and assumed that it consist of artemia that had ingested or attached ETP-1. Standard soft agar assay was performed [23] in series of dilutions 10 1 -10 8 for the Sup1, W1, W2, and F1 at both 2 and 4 h to determine the presence of ETP-1.…”

“…Gut tissue (n = 3) was extracted at 7 days post ETP-1-enriched artemia feeding, snap frozen in liquid nitrogen, and stored in − 80°C. RNA isolation, cDNA synthesis, and quantitative real-time (qRT)-PCR to evaluate relative mRNA expression levels of the target genes (primer list; Table S1) were carried out as described previously [23,24], and gene expression data were analyzed according to the 2 −ΔΔCt method [25].…”

“…In the present study, we focused on to investigate whether E. tarda-infecting phage ETP-1 [23] could attach to the artemia or ingest by the artemia (ETP-1-enriched artemia). Moreover, ETP-1 distribution, abundance, persistency, or decay in zebrafish were investigated to find out whether the feeding of ETP-1enriched artemia is an efficient phage incorporation method to fish.…”