Using Phage PSM-1 to Control Shewanella marisflavi Infection in Juvenile Sea Cucumber, Apostichopus japonicus

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• 作者：Zhen Li ; Yaxiong Song ; Xitao Wang ; Jiancheng Zhang ; Lili Wang ; Xiaoyu Li and Yongping Xu
• 刊名：Journal of the World Aquaculture Society
• 出版年：2017
• 出版时间：February 2017
• 年：2017
• 卷：48
• 期：1
• 页码：113-121
• 全文大小：689K
• ISSN：1749-7345

文摘

Shewanella marisflavi is considered responsible for infection in juvenile sea cucumber, Apostichopus japonicas. A bacteriophage specific to S. marisflavi was isolated from seafood wholesale market sewage and designated as vB_SmaM_PSM (PSM-1). The phage was classified as a member of the Myoviridae family by negative staining transmission electronic microscopy. The stability of phage PSM-1 was observed after treatment with different temperature gradients and pH values. The results showed that the lytic activity of phage PSM-1 was optimum at 28 C with a pH of 7.0 and ceased at temperatures higher than 60 C. A one-step growth curve analysis of the phage revealed eclipse and latent periods of 20 and 40 min, respectively, with a burst size of 219 plaque forming units per infected cell. The ability of phage PSM-1 to inhibit the growth of S. marisflavi AP629 was tested in vitro using the phage with three multiplicity of infection (MOI) values of 0.1, 1, and 10. All treated cultures that produced an inhibition of the growth of S. marisflavi AP629 were compared with the untreated culture, and the treatment group with a MOI value of 10 showed the highest inhibition effect among the three doses. In an in vivo performance experiment, the sea cucumbers (15–20 g) were randomly assigned to five groups (one negative control, one antibiotic treatment group, and three phage treatment groups) in a phage injection trial as well as a phage immersion trial. All groups were infected with S. marisflavi strain AP629 (3.3 × 10⁶ colony forming units/g, LD₅₀ [lethal dose 50%] level) by intraperitoneal injection. After 8 d of observation, the survival rates ranged from 40 to 80% in all phage treatment groups, while 10% in the negative control group. The optimal therapeutic time points of the two trials were also determined. The results showed that using phage prior to infection could be a good choice to protect sea cucumbers. The overall results of this experiment indicate that using phage may be a feasible biological control agent to prevent S. marisflavi infection in sea cucumbers.