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United States Department of Agriculture

Agricultural Research Service

Title: Survival of Streptococcus Agalactiae from Frozen Fish Following Natural and Experimental Infections

Authors
item EVANS, JOYCE
item Wiedenmayer, Alyssa
item Klesius, Phillip
item SHOEMAKER, CRAIG

Submitted to: Aquaculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 14, 2003
Publication Date: April 13, 2004
Citation: Evans, J.J., Wiedenmayer, A.A., Klesius, P.H., Shoemaker, C.A. 2004. Survival of Streptococcus agalactiae from frozen fish following natural and experimental infections. Aquaculture. 233:15-21.

Interpretive Summary: We evaluated the survival of Streptococcus agalactiae from naturally infected wild mullet (Liza klunzingeri) and experimentally infected Nile tilapia (Oreochromis niloticus) frozen at -20 EC and -70 EC, respectively, for an extended period of time. The brain, eye, head kidney and intestine of individually frozen wild mullet (N=22), testing positive for S. agalactiae at the time of collection during an S. agalactiae epizootic in Kuwait Bay in 2001, were re-sampled after nine months. Nares and intestines, not previously sampled were also evaluated. Tilapia were inoculated with either 5.6 H102 colony forming units (CFU)/fish or 4.5 H106 CFU/fish and S. agalactiae survival assessed from frozen tissues after 7, 14, 30, or 180 d. Streptococcus agalactiae was recovered from nare, brain, eye, and head kidney of 100% of the infected frozen mullet after nine months post-freezing. The nare, brain, head kidney of 100% of the experimentally infected tilapia were culture positive at 7, 14, 30 and 180 d post-freezing. The use of frozen fish may prove to be a useful, alternative to fresh fish for recovering pathogenic streptococci in instances when fresh fish diagnostic analysis are unavailable or impractical. Furthermore, archived frozen fish can be used for retrospective microbiological analyses of streptococcal infection from multiple or different tissues.

Technical Abstract: We evaluated the survival of Streptococcus agalactiae from naturally infected wild mullet (Liza klunzingeri) and experimentally infected Nile tilapia (Oreochromis niloticus) frozen at -20EC and -70EC, respectively, for an extended period of time. The brain, eye, head kidney, and intestine of individually frozen wild mullet (N=22), testing positive for S. agalactiae at the time of collection during an S. agalactiae epizootic in Kuwait Bay in 2001, were re-sampled after nine months. Nares and intestines, not previously sampled, were also evaluated. Tilapia were inoculated with either 5.6 H102 colony forming units (CFU)/fish or 4.5 H106 CFU/fish and S. agalactiae survival assessed from frozen tissues after 7, 14, 30, or 180 days. Streptococcus agalactiae was recovered from nare, brain, eye, and head kidney of 100% of the infected frozen mullet after nine months post-freezing. The nare, brain, head kidney of 100% of the experimentally infected tilapia were culture positive at 7, 14, 30, and 180 days post-freezing. The use of frozen fish may prove to be a useful alternative to fresh fish for recovering pathogenic streptococci in instances when fresh fish diagnostic analysis are unavailable or impractical. Furthermore, archived frozen fish can be used for retrospective microbiological analyses of streptococcal infection from multiple or different tissues.

Last Modified: 7/28/2014