Phenotypic and genotypic heterogeneity among Streptococcus iniae isolates recovered from cultured and wild fish in North America, Central America and the Caribbean Islands

Authors: CHOU, LUCY - Ross University; GRIFFIN, MATT - Mississippi State University; FRAITES, TRELLOR - Ross University; WARE, CYNTHIA - Mississippi State University; FERGUSON, HUGH - St George'S University; KERISTEAD, NATALIE - Ross University; BRAKE, JOHN - Ross University; WILES, JUDY - Louisana State University; HAWKE, JOHN - Louisana State University; KEARNEY, MICHAEL - Louisana State University; GETCHELL, ROD - Cornell University; GAUNT, PATRICIA - Mississippi State University; SOTO, ESTEBAN - Ross University

Submitted to: Journal of Aquatic Animal Health
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/7/2014
Publication Date: 10/31/2014
Citation: Chou, L., Griffin, M.J., Fraites, T., Ware, C., Ferguson, H., Keristead, N., Brake, J., Wiles, J., Hawke, J.P., Kearney, M.T., Getchell, R., Gaunt, P., Soto, E. 2014. Phenotypic and genotypic heterogeneity among Streptococcus iniae isolates recovered from cultured and wild fish in North America, Central America and the Caribbean Islands. Journal of Aquatic Animal Health. 26:263-271.

Interpretive Summary: This study showed that the isolates of Streptococcus iniae isolated from diseased wild and cultured fish in the Americas and Caribbean are genetically different. The majority of isolates from the Americas also tended to have higher minimal inhibitory concentrations for different antibiotics and they also tended to be show more genetic variability. This could impact future vaccine development as well as treatment.

Technical Abstract: Streptococcus iniae, the etiological agent of streptococcosis in fish, is an important pathogen of cultured and wild fish worldwide. During the last decade outbreaks of streptococcosis have occurred in a wide range of cultured and wild fish in the Americas and Caribbean islands. To gain a better understanding of the epizootiology of S. iniae in the western hemisphere, over 30 S. iniae isolates recovered from different fish species and geographic locations were characterized phenotypically and genetically. Species identities were determined biochemically and confirmed by amplification and sequencing of the 16S rRNA gene. Repetitive-element palindromic PCR fingerprinting as well as biochemical and antimicrobial susceptibility profiles suggest that a single strain of S. iniae was responsible for two different disease outbreaks among reef fishes in the Caribbean, one in 1999 and another in 2008. Interestingly, a majority of the isolates recovered from cultured fish in the Americas were genetically distinct from the Caribbean isolates and exhibited a trend toward higher minimal inhibitory concentration with respect to several antibiotics as well as greater genetic variability. The biological significance of this genetic variability is unclear, but it could have implications for future vaccine development and treatment.