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Streptococcus pyogenes colonies on blood agar
microscope picture gram positive cocci in chains

Streptococcus pyogenes

Group A streptococci

Colonies of Streptococcus pyogenes cultivated on blood agar. Cultivation 24 hours in an aerobic atmosphere enriched with 5% carbon dioxide. Colonies are surroundend by a zone of beta-hemolysis.

Streptococcus pyogenes is a spherical, Gram-positive bacterium that is the cause of Group A streptococcal infections. S. pyogenes displays streptococcal group A antigen on its cell wall. S. pyogenes typically produces large zones of beta-hemolysis (the complete disruption of erythrocytes and the release of hemoglobin) when cultured on blood agar plates, and are therefore also called Group A (beta-hemolytic) Streptococcus (abbreviated GABHS).
Text: Wikipedia
Spherical or ovoid cells in chains of short to medium length (4-10 cells).