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United States Department of Agriculture

Agricultural Research Service

Research Project: Integrated Aquatic Animal Health Strategies

Location: Aquatic Animal Health Research

Title: Development and efficacy of a noviobiocin-resistant Streptococcus iniae as a novel vaccine in Nile tilapia (Oreochromis niloticus)

Authors
item Pridgeon, Yuping
item Klesius, Phillip

Submitted to: Vaccine
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 12, 2011
Publication Date: July 27, 2011
Repository URL: http://hdl.handle.net/10113/55582
Citation: Wei Pridgeon, Y., Klesius, P.H. 2011. Development and efficacy of a noviobiocin-resistant Streptococcus iniae as a novel vaccine in Nile tilapia (Oreochromis niloticus). Vaccine. 29: 5986-5993.

Interpretive Summary: A novel attenuated Streptococcus iniae vaccine, ISNO, was developed through selection for novobiocin resistance. The safety of this novel vaccine was then evaluated in Nile tilapia through injection. When tilapia were injected with 2×107 colony-forming units of the attenuated S. iniae vaccine strain, no fish died. However, when the same age and same size group of male tilapia were IP injected with 2×107 and 1×105 CFU of the virulent parent strain of S. iniae, 100 and 90% fish died, respectively. Backpassage safety studies of ISNO revealed that ISNO was unable to revert back to a virulent state. When vaccinated fish were challenged with virulent parent strain of S. iniae, relative percent survival (RPS) values of vaccinated fish were 100, 100, 100, 89, and 75, respectively, at 14, 28, 60, 90, and 180 days post ISNO vaccination. The RPS values of ISNO vaccinated fish at 60 dpv were 78, 90, 100, 100, and 100%, respectively, against infections by five heterologous virulent strains of S. iniae (F3CB, 102F1K, 405F1K, IF6, and ARS60). When tilapia were IP vaccinated by ISNO at dose of 1×102, 1×103, 1×104, 1×105, 1×106, and 1×107 CFU/fish, RPS values at 28 dpv were 81, 94, 100, 100, 100, and 100%, respectively. At 28 dpv, RPS of vaccinated fish by ISNO through bath immersion was 88%. Our results suggest that ISNO could be used as a novel safe and efficacious vaccine to protect Nile tilapia from S. iniae infections.

Technical Abstract: A novel attenuated Streptococcus iniae vaccine was developed from a virulent strain of Streptococcus iniae (ISET0901) through selection for novobiocin resistance (therefore named ISNO). The safety of ISNO was then evaluated in Nile tilapia (Oreochromis niloticus) through intraperitoneal (IP) injection. When male tilapia (average weight 10g) were IP injected with 2×107 colony-forming units (CFU) of the attenuated S. iniae vaccine strain, no fish died. However, when the same age and same size group of male tilapia were IP injected with 2×107 and 1×105 CFU of the virulent parent strain of S. iniae, 100 and 90% fish died, respectively. Backpassage safety studies of ISNO revealed that ISNO was unable to revert back to a virulent state. When IP vaccinated fish were challenged by the virulent ISET0901 strain of S. iniae, relative percent survival (RPS) values of vaccinated fish were 100, 100, 100, 89, and 75, respectively, at 14, 28, 60, 90, and 180 days post ISNO vaccination (dpv). The RPS values of ISNO vaccinated fish (IP vaccination) at 60 dpv were 78, 90, 100, 100, and 100%, respectively, against infections by five heterologous virulent strains of S. iniae (F3CB, 102F1K, 405F1K, IF6, and ARS60). When tilapia were IP vaccinated by ISNO at dose of 1×102, 1×103, 1×104, 1×105, 1×106, and 1×107 CFU/fish, RPS values at 28 dpv were 81, 94, 100, 100, 100, and 100%, respectively. At 28 dpv, RPS of vaccinated fish by ISNO through bath immersion (1×107 CFU/ml) was 88%. Our results suggest that ISNO could be used as a novel safe and efficacious vaccine to protect Nile tilapia from S. iniae infections.

Last Modified: 4/16/2014
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