Streptococcus iniae

Streptococcus iniae is a species of Gram-positive bacteria in the genus Streptococcus. This bacterium is a significant pathogen in aquaculture, causing disease in fish such as the tilapia, red drum, and hybrid striped bass. It is also known to cause rare but serious infections in humans, particularly in individuals who handle fish or are immunocompromised.

Taxonomy

The bacterium was first described in 1976, isolated from an outbreak of disease in Amazon freshwater dolphins. It was named Streptococcus iniae due to its initial identification in the Amazon river dolphin (Inia geoffrensis).

Pathogenicity

Streptococcus iniae is a major pathogen in aquaculture, causing bacterial meningitis and septicemia in fish. The bacterium is highly virulent, with outbreaks often resulting in high mortality rates. It is particularly problematic in intensive farming systems where high stocking densities and stress can promote disease spread.

In humans, S. iniae can cause a range of infections, including cellulitis, meningitis, endocarditis, and septic arthritis. Most human cases have been associated with handling fish, particularly in individuals with pre-existing skin lesions or immunocompromised states.

Diagnosis and Treatment

Diagnosis of S. iniae infection in fish is typically based on clinical signs, histopathology, and bacterial culture. In humans, diagnosis is usually confirmed by blood culture.

Treatment of S. iniae infection in fish involves the use of antibiotics, often in combination with management strategies to reduce stress and improve water quality. In humans, the bacterium is usually susceptible to penicillin and other beta-lactam antibiotics, although resistance has been reported.

Prevention

Prevention of S. iniae infection in aquaculture involves good husbandry practices, including maintaining optimal water quality, minimizing stress, and avoiding overcrowding. Vaccines are also available for some species of fish.

In humans, prevention involves careful handling of fish, particularly for individuals with skin lesions or who are immunocompromised.

See Also

• Streptococcus
• Aquaculture
• Fish diseases and parasites