Restriction fragment length polymorphisms of 16S rDNA and of whole rRNA genes (ribotyping) of Streptococcus iniae strains from the United States and Israel.

Streptococcus iniae (junior synonym S. shiloi) isolated from tilapia and trout in Israel and in the United States were subtyped by restriction length polymorphism (RFLP) based on PCR amplified 16S rDNA and by ribotyping. 16S rDNA RFLP discriminated between S. iniae and other fish pathogens but not between S. iniae strains. HindIII and EcoRI ribotypes of S. iniae discriminated American from Israeli strains rejecting the possibility of an epidemiological link between S. iniae infections in the two countries. Israeli strains isolated from tilapia and trout could not be completely differentiated. The S. iniae ATCC 29178T (T = Type strain) strain, isolated from a freshwater dolphin belonged to a ribotype different from those of all the fish isolates.

Streptococcus shiloi, the name for an agent causing septicemic infection in fish, is a junior synonym of Streptococcus iniae.

Streptococcus shiloi strains, including the type strain, which were isolated in Israel and the United States, and Streptococcus iniae ATCC 29178(T) (T = type strain) are phenotypically identical (as determined with API 20STREP and API 50CH kits; beta-hemolytic on sheep blood agar). DNA-DNA hybridization experiments revealed levels of homology of 77 to 100%. Thus, S. shiloi should be considered a junior synonym of S. iniae. This bacterium is a major fish pathogen that is distributed worldwide.