ARS | Publication request: Development and efficacy of a novobiocin-resistant Streptococcus iniae as a novel vaccine in Nile tilapia (Oreochromis niloticus)

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: June 16, 2011
Publication Date: August 1, 2011
Citation: Wei Pridgeon, Y., Klesius, P.H. 2011. Development and efficacy of a novobiocin-resistant Streptococcus iniae as a novel vaccine in Nile tilapia (Oreochromis niloticus). IN: 17th Annual USFWS Aquaculture Drug Approval Coordination Workshop, August 1-4, 2011, Bozeman, Montana. Biologics Presentation 1-5.

Technical Abstract: A novel attenuated Streptococcus iniae vaccine was developed from a virulent strain of Streptococcus iniae through selection for novobiocin resistance. The safety of the novel vaccine (named 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 (200ul of OD540nm=1.0) colony-forming units (CFU) of the attenuated S. iniae vaccine strain, no fish died. However, when the same age and size matched tilapia were IP injected with 1×105 CFU of the virulent parent strain of S. iniae, 90% fish died, respectively. Backpassage safety studies revealed that ISNO was unable to revert back to a virulent state. When IP vaccinated fish were challenged by the virulent strain of S. iniae, relative percent survival (RPS) values of vaccinated fish at 14, 28, 60, 90, and 180 days post ISNO vaccination (dpv) were 100, 100, 100, 89, and 75%, respectively, The RPS values of ISNO vaccinated fish (IP vaccination) against infections by five heterologous virulent strains of S. iniae at 60 dpv were 78, 90, 100, 100, and 100%, respectively. 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.