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Streptococcus pyogenes, CAP agar (sheep blood agar with colistin + aztreonam). Cultivation 24 hours, aerobic atmosphere enriched with 5% CO2, 37°C. Colonies are surroundend by a wide zone of beta-hemolysis. Swab from skin.
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.
Streptococci are catalase-negative. In ideal conditions, S. pyogenes has an incubation period of approximately 1–3 days. It is an infrequent, but usually pathogenic, part of the skin flora.
It is estimated that there are more than 700 million infections world wide each year and over 650,000 cases of severe, invasive infections that have a mortality rate of 25%. Early recognition and treatment are critical; diagnostic failure can result in sepsis and death.
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