title: Bacteriophage control of Pseudomonas plecoglossicida infection in ayu Plecoglossus altivelis.
abstract: Two previously isolated phages were used to examine the therapeutic effects against Pseudomonas plecoglossicida infection in ayu Plecoglossus altivelis. Phage PPp-W4 (Podoviridae) inhibited the in vitro growth of P. plecoglossicida more effectively than Phage PPpW-3 (Myoviridae), and a mixture (PPpW-3/W-4) of the 2 phages exhibited the highest inhibitory activity. In phage therapy experiments, ayu were fed P. plecoglossicida-impregnated feed (10(7) CFU fish(-1)) and then fed phage-impregnated feed (10(7) PFU fish(-1)). Mortalities of fish receiving PPpW-3, PPpW-4, PPpW-3/W-4, and a control fish receiving no phages were 53.3, 40.0, 20.0 and 93.3%, respectively. Phage (PPpW-3/W-4)-receiving fish also showed high protection against water-borne infection with P. plecoglossicida. In a field trial, when phage (PPpW-3/W-4)-impregnated feed was administered to ayu in a pond where the disease occurred naturally, daily mortality of fish decreased at a constant level (5% d(-1)) to one-third after a 2 wk period. The causal relationship of phages in this phenomenon was verified by the long-lasting appearance of administered phages in the kidneys of the fish, and a disappearance of P. plecoglossicida from apparently healthy fish. Neither phage-resistant organisms nor phage-neutralizing antibodies were detected in diseased fish or apparently healthy fish, respectively. These results indicate the potential for phage control of the disease.
authors.affiliation: Fish Pathobiology Laboratory, Graduate School of Biosphere Science, Hiroshima University, Higashihiroshima 739-8528, Japan.
authors.forename: Se Chang
authors.initials: SC
authors.lastname: Park
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Nakai
mesh_terms: D000284:Administration, Oral; D000818:Animals; D017756:Aquaculture; D005393:Fish Diseases / Q000276:immunology / Q000382:microbiology / Q000517:prevention & control*; D007273:Injections, Intramuscular / Q000662:veterinary; D036441:Osmeriformes / Q000382:microbiology*; D011549:Pseudomonas / Q000502:physiology / Q000821:virology*; D011552:Pseudomonas Infections / Q000276:immunology / Q000517:prevention & control / Q000662:veterinary*; D017105:Pseudomonas Phages / Q000502:physiology*; D016019:Survival Analysis; D014871:Water Microbiology