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''Streptococcus iniae'' is a species of Gram-positive, sphere-shaped bacterium belonging to the genus ''Streptococcus''. Since its isolation from an Amazon freshwater dolphin in the 1970s, ''S. iniae'' has emerged as a leading fish pathogen in aquaculture operations worldwide, resulting in over US$100M in annual losses. Since its discovery, ''S. iniae'' infections have been reported in at least 27 species of cultured or wild fish from around the world. Freshwater and saltwater fish including tilapia, red drum, hybrid striped bass, and rainbow trout are among those susceptible to infection by ''S. iniae''. Infections in fish manifest as meningoencephalitis, skin lesions, and septicemia. ''S. iniae'' has occasionally produced infection in humans, especially fish handlers of Asian descent. Human infections include sepsis, toxic shock syndrome, and inflammation of the skin, intervertebral discs, or inner layer of the heart. Identifying ''S. iniae'' in the laboratory can be difficult, since the conventional methods used to identify streptococci yield insufficient results. It cannot be grouped by the Lancefield antigen method typically used to categorize ''Streptococci'' species. The two known serotypes can be distinguished biochemically by differences in enzyme activity. Several antibiotics have been used to treat ''S. iniae'' infections. ==History== ''Streptococcus iniae'' was first isolated in 1972, from subcutaneous abscesses in a captive specimen of Amazon River Dolphin (''Inia geoffrensis'') suffering from an infection known as "golf ball disease". The bacterium was found to be sensitive to beta-lactam antibiotics, and the dolphin was treated successfully with penicillin and tylosin. The causative organism was recognized to be a new species of ''Streptococcus'', and was given the name ''Streptococcus iniae'' in 1976.〔 Around this time, other streptococcal outbreaks occurred in Asia,〔〔 and the US;〔 some strains associated with the Japanese outbreaks〔〔〔 were later suggested to be ''S. iniae''.〔 In the 1980s, a purported new species of ''Streptococcus'', named ''S. shiloi'', was identified as one of the causes of an epidemic of meningoencephalitis (an inflammation of the brain and its surrounding membranes) affecting farmed rainbow trout and tilapia in Israel since 1986. Since ''S. shiloi'' was alpha-hemolytic, had a G+C% content of 37% and did not ferment sugar galactose, it was not classified as ''S. iniae'', which is beta-hemolytic, has a G+C% content of 32%, and ferments galactose.〔 In 1995, ''S. shiloi'' was found in fact to be beta-hemolytic, and after DNA-DNA hybridization techniques with the ATCC type ''S. iniae'' and recalculation of the G+C% content, was reclassified by the same group as a junior synonym of ''S. iniae''.〔 Phylogenetic analyses based on 16S ribosomal DNA suggest that ''S. iniae'' is closely related to other streptococcal pathogens of humans and animals.〔〔 Specifically, it is clustered in the pyogenic group, along with other pathogenic streptococci such as ''S. pyogenes'', ''S. agalactiae'', ''S. uberis'', ''S. canis'', ''S. porcinus'', ''S. phocae'', and ''S. intestinalis''. Of these related species, it is most closely related to ''S. porcinus''.〔〔 Genomic restriction fragment analysis of diverse host and geographical panels of ''S. iniae'' isolates has shown common profiles between virulent fish and human strains,〔〔〔 though multiple pulsed field gel electrophoresis patterns have been identified among human isolates.〔〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Streptococcus iniae」の詳細全文を読む スポンサード リンク
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