Fish Pathology
Online ISSN : 1881-7335
Print ISSN : 0388-788X
ISSN-L : 0388-788X
Research Articles
Phage Therapy against β-hemolytic Streptococcicosis of Japanese Flounder Paralichthys olivaceus
Satoru MatsuokaTakaya HashizumeHiroyuki KanzakiEmi IwamotoPark Se ChangTerutoyo YoshidaToshihiro Nakai
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2007 Volume 42 Issue 4 Pages 181-189


We examined the therapeutic effect of Streptococcus iniae phages isolated from fish culture environments against experimental streptococcicosis of Japanese flounder Paralichthys olivaceus. Phage sensitivity tests with a double agar method revealed that 31 of 35 S. iniae strains from the flounder have a similar sensitivity to six phage isolates. In phage therapy experiments, fish were injected intraperitoneally (IP) with S. iniae PSi402 and 1 h later IP-injected with a mixture of two or four phage isolates, and observed at 25°C for 2 wk. Mortalities of fish receiving phages were significantly lower than those of control fish without phage-treatment in all four trials. The effect of phage treatment was also demonstrated even at 24 h post-infection, when cell numbers of S. iniae were 107.4 and 104.5 CFU/g in the kidneys and brains of fish, respectively. However, as phage-resistant S. iniae were frequently isolated from dead fish in the phage-treated group, further investigations are required to establish phage therapy of the disease.

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© 2007 The Japanese Society of Fish Pathology
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