Location: Aquatic Animal Health Research
Title: Development of live attenuated sparfloxacin-resistant Streptococcus agalactiae polyvalent vaccines to protect Nile tilapia Authors
Submitted to: International Aquaculture Meeting
Publication Type: Proceedings
Publication Acceptance Date: June 17, 2013
Publication Date: October 6, 2013
Citation: Wei Pridgeon, Y., Klesius, P.H. 2013. Development of live attenuated sparfloxacin-resistant Streptococcus agalactiae polyvalent vaccines to protect Nile tilapia. 10th International Symposium on Tilapia in Aquaculture. p. 24. Technical Abstract: To develop attenuated bacteria as potential live vaccines, sparfloxacin was used in this study to modify 40 isolates of Streptococcus agalactiae. Majority of S. agalactiae used in this study were able to develop at least 80-fold resistance to sparfloxacin. When the virulence of the sparfloxacin-resistant S. agalactiae isolates were tested in 10-12g Nile tilapia by intraperitoneal injection at dose of 2 X 107 CFU/fish, 31 were found to be avirulent to fish. Of the 31 avirulent sparfloxacin-resistant S. agalactiae isolates, 30 provided 75% to 100% protection to 10-12g Nile tilapia against challenges with a virulent S. agalactiae isolate Sag 50. When the virulence of the 30 sparfloxacin-resistant S. agalactiae isolates was tested in 3-5g Nile tilapia by intraperitoneal injection at dose of 2 X 107 CFU/fish, six were found to be avirulent to 3-5g Nile tilapia. Of the six avirulent sparfloxacin-resistant S. agalactiae isolates, four provided 3-5g Nile tilapia 100% protection against challenges with homologous isolates, including Sag 97-spar isolate that was non-hemolytic. However, Sag 97-spar failed to provide broad cross-protection against challenges with heterologous isolates. When Nile tilapia was vaccinated with a polyvalent vaccine consisting of 30 sparfloxacin-resistant S. agalactiae isolates at dose of 2 X 106 CFU/fish, the polyvalent vaccine provided significant (P<0.001) protection to both 3-5g and 15-20g Nile tilapia against challenges with 30 parent isolates of S. agalactiae. Taken together, our results suggest that a polyvalent vaccine consisting of various strains of S. agalactiae might be essential to provide broader protection to Nile tilapia against infections caused by S. agalactiae.