Characterization of Isolates of Streptococcus agalactiae from Diseased Farmed and Wild Marine Fish from the U.S. Gulf Coast,Latin America,and Thailand |
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| Authors: | Esteban Soto Rui Wang Judy Wiles Wes Baumgartner Christopher Green John Plumb |
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| Affiliation: | 1. Department of Biomedical Sciences, School of Veterinary Medicine, Ross University, Post Office Box 334, Basseterre, St. Kitts, West Indies;2. Present address: Department of Pathobiological Sciences, School of Veterinary Medicine, Louisiana State University, 1909 Skip Bertman Drive, Baton Rouge, Louisiana 70803, USA;3. Department of Pathobiological Sciences, School of Veterinary Medicine, Louisiana State University, 1909 Skip Bertman Drive, Baton Rouge, Louisiana 70803, USA;4. Department of Pathobiology and Population Medicine, College of Veterinary Medicine, Mississippi State University, 240 Wise Center Drive, Mississippi State, Mississippi 39762, USA;5. Aquaculture Research Station, Louisiana State University Agricultural Center, 2410 Ben Hur Road, Baton Rouge, Louisiana 70820, USA;6. School of Fisheries, Aquaculture, and Aquatic Sciences, Auburn University, 203 Swingle Hall, Auburn, Auburn, Alabama 36830, USA;7. Retired |
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| Abstract: | We examined Lancefield serogroup B Streptococcus isolates recovered from diseased, cultured hybrid Striped Bass (Striped Bass Morone saxatilis × White Bass M. chrysops) and wild and cultured Gulf Killifish Fundulus grandis from coastal waters of the U.S. Gulf of Mexico (Gulf coast) and compared those isolates to strains from tilapias Oreochromis spp. reared in Mississippi, Thailand, Ecuador, and Honduras and to the original Gulf coast strain identified by Plumb et al. (1974 Plumb, J.A., J.H. Schachte, J.L. Gaines, W. Peltier, and B. Carroll. 1974. Streptococcus sp. from marine fishes along the Alabama and northwest Florida coast of the Gulf of Mexico. Transactions of the American Fisheries Society 103:358–361.[Taylor &; Francis Online], [Web of Science ®] , [Google Scholar]). The isolates were subjected to phylogenetic, biochemical, and antibiotic susceptibility analyses. Genetic analysis was performed using partial sequence comparison of (1) the 16S ribosomal RNA (rRNA) gene; (2) the sipA gene, which encodes a surface immunogenic protein; (3) the cspA gene, which encodes a cell surface-associated protein; and (4) the secY gene, which encodes components of a general protein secretion pathway. Phylogenies inferred from sipA, secY, and cspA gene sequence comparisons were more discriminating than that inferred from the 16S rRNA gene sequence comparison. The U.S. Gulf coast strains showed a high degree of similarity to strains from South America and Central America and belonged to a unique group that can be distinguished from other group B streptococci. In agreement with the molecular findings, biochemical and antimicrobial resistance analyses demonstrated that the isolates recovered from the U.S. Gulf coast and Latin America were more similar to each other than to isolates from Thailand. Three laboratory challenge methods for inducing streptococcosis in Gulf Killifish were evaluated—intraperitoneal (IP) injection, immersion (IMM), and immersion plus abrasion (IMMA)—using serial dilutions of S. agalactiae isolate LADL 97-151, a representative U.S. Gulf coast strain. The dose that was lethal to 50% of test fish by 14 d postchallenge was approximately 2 CFU/fish via IP injection. In contrast, the fish that were challenged via IMM or IMMA presented cumulative mortality less than 40% by 14 d postchallenge.Received July 31, 2014; accepted March 11, 2015 |
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