Streptococcus dysgalactiae

Streptococcus dysgalactiae (Beta haemolytic Streptococcus Lancefield Group G) on Columbia Horse Blood Agar - Detail

Streptococcus dysgalactiae is a species of bacteria belonging to the genus Streptococcus. It is a significant pathogen in both humans and animals, causing a range of infections. This bacterium is Gram-positive, meaning it has a thick cell wall that retains the crystal violet stain used in the Gram staining procedure. Streptococcus dysgalactiae is further classified into two subspecies based on genetic and biochemical characteristics: Streptococcus dysgalactiae subsp. equisimilis and Streptococcus dysgalactiae subsp. dysgalactiae. The former is more commonly associated with human infections, while the latter is often found in animals.

Characteristics

Streptococcus dysgalactiae is characterized by its spherical shape and tendency to form chains. It is a facultative anaerobe, capable of growing in both the presence and absence of oxygen. This bacterium is also beta-hemolytic, meaning it can completely lyse red blood cells, a property that is used to identify it in laboratory cultures.

Pathogenicity

Streptococcus dysgalactiae can cause a variety of infections. In humans, it is responsible for pharyngitis, skin and soft tissue infections, and, less commonly, invasive diseases such as bacteremia and endocarditis. In animals, particularly cattle, it causes mastitis, an infection of the mammary gland that is a significant concern in the dairy industry due to its impact on milk production.

Diagnosis and Treatment

Diagnosis of Streptococcus dysgalactiae infections typically involves the isolation and identification of the bacterium from clinical specimens using culture methods. The beta-hemolytic activity on blood agar and other biochemical tests help in identifying the species. Treatment usually involves antibiotics, with penicillin being the drug of choice. However, the emergence of antibiotic resistance necessitates susceptibility testing to guide therapy.

Prevention

Preventive measures against Streptococcus dysgalactiae infections include maintaining good hygiene practices to avoid skin infections and implementing control measures in healthcare settings to prevent nosocomial infections. In the agricultural sector, prevention strategies focus on improving animal health through vaccination and hygiene practices to reduce the incidence of mastitis.