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Strain variation and geographic endemism in Streptococcus iniae
1Israel Oceanographic and Limnological Research, National Center for Mariculture, PO Box 1212, Eilat 88112, Israel. kvitt@ocean.org.il
Diseases of Aquatic Organisms
|December 9, 2004
Summary
Distinct Streptococcus iniae strains cause disease in Israeli aquaculture. Molecular analysis revealed geographic differences, with marine and freshwater isolates being genetically separate, impacting fish health.
Area of Science:
- Microbiology
- Aquatic Animal Health
- Molecular Biology
Background:
- Streptococcus iniae causes significant losses in aquaculture.
- Understanding S. iniae strain variation is crucial for disease management.
Purpose of the Study:
- To molecularly characterize Israeli Streptococcus iniae isolates.
- To compare them with foreign isolates and identify strain variations.
- To determine if distinct strains affect different aquatic environments.
Main Methods:
- Biochemical profiling for initial identification.
- Polymerase Chain Reaction (PCR) amplification and 16S rDNA sequencing.
- Randomly Amplified Polymorphic DNA (RAPD) analysis.
- Amplified Fragment Length Polymorphism (AFLP) analysis.
Main Results:
- 16S rDNA sequencing confirmed S. iniae and identified a new variant.
- RAPD separated isolates into two main groups.
- AFLP analysis revealed a homogeneous cluster for marine isolates and distinct clusters for freshwater and foreign isolates.
- Significant genetic distance between marine and freshwater S. iniae strains was observed.
Conclusions:
- Distinct S. iniae strains are responsible for streptococcosis in Israeli marine and freshwater aquaculture.
- AFLP is a superior method for differentiating S. iniae strains compared to RAPD.
- A correlation between strain variation and geographic endemism in S. iniae was established.