Alpha-hemolytic

Alpha-hemolytic streptococci are a type of bacteria that produce a green pigment when grown on blood agar, a type of laboratory medium. This green pigment is a result of the partial (alpha) hemolysis of red blood cells, which differentiates these bacteria from beta-hemolytic streptococci, which completely lyse red blood cells, and gamma-hemolytic streptococci, which do not lyse red blood cells.

Characteristics

Alpha-hemolytic streptococci are Gram-positive bacteria, meaning they retain the crystal violet stain used in the Gram stain procedure. They are also catalase-negative, which differentiates them from Gram-positive cocci that are catalase-positive, such as Staphylococcus species.

Pathogenesis

Some species of alpha-hemolytic streptococci, such as Streptococcus pneumoniae and Streptococcus viridans, are part of the normal flora of the human body, but can cause disease under certain conditions. For example, S. pneumoniae is a common cause of pneumonia, meningitis, and otitis media, while S. viridans can cause endocarditis in individuals with damaged heart valves.

Diagnosis

Diagnosis of infections caused by alpha-hemolytic streptococci is typically made by culture of the bacteria from a clinical specimen, such as blood or sputum. The bacteria can be identified by their characteristic appearance on blood agar, as well as by other laboratory tests.

Treatment

Treatment of infections caused by alpha-hemolytic streptococci depends on the specific species and the site of infection, but often involves antibiotics such as penicillin or cephalosporins.

Alpha-hemolytic Resources
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